February 8, 2012


What are the side effects of aspartame, stevia, and other sugar substitutes?

by Peter Attia

Read Time 10 minutes

Once you realize how harmful sugar is (by sugar, of course, I mean sucrose and high fructose corn syrup or HFCS, primarily, but also the whole cast of characters out there like cane sugar, beet sugar, dextrose, corn syrup solids, and others that masquerade as sugar), you inevitably want to understand the impact of substituting non-sugar sweeteners for sugar, should you still desire a sweet taste.

If you’re not yet convinced sugar is a toxin, it’s probably worth checking out my post, Sugar 101, and the accompanying lecture by Dr. Lustig. Sugar is, tragically, more prevalent in our diets today than we realize – our intake of sugar today is about 400% of what it was in 1970.  And it’s not just in the “obvious” places, like candy bars and soda drinks, where sugar is showing up, either.  It’s in salad dressings, pasta sauces, cereals, “healthy” sports bars and drinks, low-fat “healthy” yogurt, and most lunch meats, just to name a few places sugar sneaks into our diet.

I know some people have an aversion to aspartame (i.e., Nutrasweet, Equal) over sucrose (i.e., table sugar, sucrose, or HFCS).  In other words they think Coke is “better” that Diet Coke because it uses “real” sugar instead of “fake” sugar.   If you find yourself in this camp, but you’re now realizing “real” sugar is a toxin, this poses a bit of a dilemma.

There are two things I think about when considering the switch from sugar to non-sugar substitute sweeteners:

  1. Are non-sugar sweeteners more or less chronically harmful than sugar?
  2. What are the immediate metabolic impacts of consuming these products, relative to sugar?

Let’s address these questions in order.

Question 1: Are artificial (i.e., non-sugar or substitute) sweeteners more chronically harmful than sucrose/HFCS?

There’s no shortage of fear out there that consuming aspartame, sucralose, or other non-sugar substitute sweeteners will lead to chronic diseases like cancer or heart disease.  However, there is no credible evidence of this in humans.  One can actually make a convincing case that no substance ingested by humans has been more thoroughly tested by the FDA than aspartame.  The former Commissioner of the FDA noted, “Few compounds have withstood such detailed testing and repeated, close scrutiny, and the process through which aspartame has gone should provide the public with additional confidence of its safety.”  While it might be the case that you can harm a rat with aspartame, it seems you need to force the rat to eat its bodyweight in aspartame every day for a year to do so (I’m being a bit facetious, but you get the idea).   In fact, even water would be harmful to us in the quantities required to render aspartame harmful if we extrapolate from rat studies.

Since its invention/discovery in 1965, there is not a single well-documented case of chronic harm to a human from ingesting aspartame, and prior to its approval for human consumption in the early 1980’s it had been studied in approximately 100 independent studies.  A possible exception to this might be in the rare person with phenylketonuria (PKU).  Such folks lack an enzyme required to metabolize a breakdown product of aspartame.

So, aside from the rare person with PKU, does this mean aspartame is 100% harmless?  Not necessarily. 100% harmless is a pretty high bar.  “Harmless,” using air travel as an analogy, is not getting on an airplane at all.  Consuming aspartame is more like getting on a commercial airplane – statistically speaking you are very safe, but something bad could happen that we’re not aware of yet.  Consuming sugar in the amounts we typically do, by contrast, is downright harmful.  “Harmful,” by the air travel analogy, is not only getting on an airplane but skydiving with a poorly-packed parachute – you might make it, but you’re really taking a chance.

As far as other non-sugar substitute sweeteners go (e.g., sucralose, saccharin, stevia, xylitol), the same logic holds except that we don’t have quite as much data on them because most of them (see figure, below, for the most popular ones) haven’t been on our tables quite as long as aspartame.  However, to date there are no data linking these substances to the diseases people tend to erroneously link them to in casual conversation.


Sugar substitutes with molecular structures

Question 2: What are the metabolic differences between sugar and non-sugar substitute sweeteners?

The metabolic effects of table sugar (sucrose) and high fructose corn syrup (HFCS) are well understood, so I won’t review them again.  If you want a quick review of sugar and why it’s probably as chronically harmful as tobacco, see my previous post on the topic.  Also, Dr. Lustig and his colleagues last week published a paper in the journal Nature titled, The toxic truth about sugar, which you may want to check out if you have a subscription to Nature.  The press picked this up in spades, also, and here is one such story.

So how do non-sugar substitute sweeteners compare to sucrose/HFCS in the acute or immediate metabolic phase?  Most non-sugar sweeteners (e.g., aspartame, saccharin, sucralose, stevia) are much more potent in their sweetness relative to sucrose, and therefore require a fraction of the amount to give the same “sweetness” as sucrose.  So for these sweeteners, only a fraction of the substance is required for equal sweetness.  That’s why when you look at a can of Diet Coke it has no calories in it.  The amount of aspartame that’s used is so small (given its sweetness), it doesn’t even add a calorie worth of energy.  Hence, we consume a fraction of them, relative to “real” sugar to get the same sweetness.

Other non-sugar substitute sweeteners, such as alcohol sugars (e.g., xylitol, sorbitol), are not actually sweeter than sucrose, but they have very different metabolic and digestive properties.  Furthermore, one actually uses similar amounts of these sweeteners, relative to sucrose (e.g., substituting an alcohol sugar in the place of sucrose occurs at about a one-to-one ratio).  In other words, when consuming alcohol sugars you actually ingest non-zero calories of them.  This is why you’ll note non-zero amounts of them when you look at the ingredient labels of foods containing them.  Even a piece of gum sweetened with alcohol sugars contains 1 to 2 grams per piece.  While an excess of alcohol sugars can cause gastrointestinal distress (e.g., if you overdo it on these you can get diarrhea), in most people they do not cause secretion of insulin from the pancreas due to their distinct chemical structure (see figure of their structures, above).

The same is true for the first group of non-sugar substitute sweeteners I mentioned (e.g., aspartame, saccharin, sucralose), with respect to the lack of insulin response.  In addition to studies confirming this, I’ve also documented this in myself for xylitol (my personal favorite), aspartame (Equal), and sucralose (Splenda).  I cannot speak to the other substitute non-sugar sweeteners in myself, but these three compounds seem to pass through my digestive tract without ever alerting my pancreas (i.e., without stimulating insulin).  When I consume these non-sugar sweeteners neither my blood glucose nor insulin levels rise.

I should point out that some people have noted/suggested a cephalic insulin response to non-sugar substitute sweeteners.  A cephalic insulin response occurs when the pancreas begins to secrete insulin before the “meal” actually gets into the bloodstream – the usual step required for the pancreas to secrete insulin.  In other words, the anticipation of the meal leads to the release of insulin.  This has been documented in humans, and a few studies have attempted to elucidate the mechanism indirectly by using various drugs to attempt to block this response.  Furthermore, some have suggested that you can still experience the harmful effects of regular soda while consuming an equal amount of diet soda.  It’s not clear to me this is true.  First, this hypothesis has never been studied rigorously (i.e., prospectively and with random assignment in a controlled setting).   Second, if there is some cephalic insulin response to non-sugar sweeteners, it is probably significantly less than that of sugar in both magnitude and duration, based on the studies I’ve read.  To reiterate a common theme – this phenomenon is probably minimal in most people but significant in others.  When I work with people who seem to be doing everything “right” but can’t seem to make improvements (e.g., fat loss), I will usually suggest removing all non-sugar substitute sweeteners to test this hypothesis.

Lastly, there has been some recent discussion about how diet soda may cause even more harm than regular soda.  A few observational studies have commented on this, including a study released last week in the Journal of General Internal Medicine.  Due to time and space, I’m not going to comment broadly on this paper in this post (though I will write a great deal more about this sort of study in the future).  I do want to make one very important point that is true of virtually every study of this nature: it is impossible to make a correct inference without doing a prospective, random-assignment, controlled trial.

While the authors of this study acknowledge that “further study is warranted,” the lay press picks up the title of this paper: Diet soft drink consumption is associated with an increased risk of vascular events in the Northern Manhattan study, and fails to ask any questions.  While I am not trying to be overly critical of the study authors (whom I do not know, either personally or by reputation), I am actually quite critical of the press that like to report on bumper-sticker messages without reading the fine print.  Most people (including many policy makers, who are bombarded with this sort of bumper-sticker information) tend to form their opinions based on this sort of information.

A table from this study (Table 2) is shown below.  It’s a bit hard to read unless you click on it, which I’d suggest you do to see what I’m talking about.  The group of 163 people who consumed diet soft drinks daily had worse clinical outcomes than the group of 1,948 people who consumed no more than 1 diet soft drink per month (all self-reported).  That is, the people who drank more diet soda were more likely to have a vascular “event” (on a per person basis).  Seems pretty bad, right?  Is drinking diet soda actually causing this?

Well, let’s double-click on this question.  Note that the people who were consuming daily diet soda (relative to those not) also had a few other factors not working in their favor including higher blood pressure, higher circulating triglycerides, a higher rate of diabetes, higher BMI, lower HDL-C, higher pre-existing vascular disease, a higher rate of metabolic syndrome, and a higher rate of previous cardiac surgery just to name a few.  And in many of these factors the difference between the groups was very large (e.g., diabetes, history of peripheral vascular disease).  You will also note that both groups of diet soft drink consumers reported between 1,500 and 1,700 calories per day, below the national average, suggesting yet another problem with this sort of study — self-reporting.

The authors try to correct for this obvious shortcoming by employing a statistical technique called “adjustment.”  This means you try to “strip out” the differences between groups and see if the effect still holds.  I do not want to turn this into a detailed post on elaborate statistics (a topic I greatly enjoy), but it’s REALLY important that you understand why this is a dangerous way to conduct science.  The reason this is “dangerous” is that it only proves an association exists, not that there is any causal link between drinking diet soda and getting cardiovascular disease.

If anyone is really interested in the details of this, I actually reached out to my thesis adviser who did his Ph.D. in applied statistics at Berkeley at the age of 20 (and is one of the smartest people I’ve ever met).  Just to make sure I hadn’t gone too far off the reservation, I asked him his view.  Here was his response:

Do I buy the analysis? The unadjusted data (Table 2) is pretty hard to disagree with. The adjusted results are open to debate, because the conclusions depend on the form of the model that the authors proposed.  A Cox proportional hazards model assumes that the predictors enter linearly into the model. This form is chosen for computational and mathematical convenience, not because anybody has a convincing argument for why the model is correct. But it’s the most popular model out there for survival analysis.

Remember also that the study is observational, not a controlled experiment. The authors can’t conclude that the diet soda is the cause of the greater disposition toward a vascular event, only that there is an association.

My translation: Taken as-is (i.e., unadjusted) there is no way to draw any conclusion from this.  After statistical adjustment, you might be able to make the case that it’s worth looking into things further, but as it stands there is only an association between consuming diet soda and having a vascular event.

Want another way to think about? Think of a simple (and silly) example:  I once read (I’m not making this up) that people with red cars are more likely to get into car accidents.  Let’s assume this is true (though I can’t confirm it).  Does it mean owning a red car causes you to have a higher chance of getting into a car accident? Or is it more likely that someone who buys a red car may drive in such way that they are more likely to have an accident?  My guess is, even if this correlation between car color and accident frequency were true, there is no causal information contained within it.


Table 2 JGIM paper

Yes, it is possible the reporting of all behavior (e.g., intake) was accurate, and yes it is possible that, even when adjusting for these pre-existing differences between the groups, the outcome would have been the same.  But is it likely? It is very hard for me to believe this.

There is a reason I refer (only half-jokingly) to observational epidemiology studies as “scientific weapons of mass destruction.”  If you remember nothing else I write or say, please remember this: Never confuse association with causation.  If we want to definitively know the answer to this question, we need to design a prospective, well-controlled, random-assignment experiment.

So what is the upshot of all of this?

I would argue (along with a legion of others) that once you eliminate sugar from your diet, your cravings for sugar actually vanish.  So the question, rather than, Is it ok to consume sugar substitutes?, may actually be: Why do we need things to be sweet in the first place?

I think this is a personal choice, and something worthy of self-experimentation.  I know many people who have eliminated everything sweet (both sugar and non-sugar sweeteners) from their diet, and within weeks they completely lose the desire or craving for sweet foods.  Others (like me) still like the occasional taste of sweet things. One of my favorite snacks is home-made whip cream (heavy cream whipped with a touch of xylitol). But the point is this: despite occasionally consuming sugar substitutes I’ve really shed my pathologic need for sweet things.   There was a day when I needed something sweet with every meal.  That’s no longer true.  I go days without ingesting anything sweet and don’t miss it.  Other days, I feel like having some xylitol-enriched whip cream, or drinking a Diet Dr. Pepper, and I do so.  Would I be better off without them?  Maybe.  But now we’re well past first-, second-, and third-order terms.  (For a refresher on the concept of “ordered terms,” check out my post on irisin).

In summary, if you must drink a sweet beverage (or add sweetener to your coffee or tea) you are better off using a substitute for sugar than you are using sugar.  But if you want to be really sure, and you want to kick the habit of needing a sweet taste, you’re probably better off avoiding substitute sweeteners altogether.  If you want to be 100% safe, drink water.  Just don’t make it bottled water (though that’s a whole other story).  And don’t fly in airplanes or drive in cars, either.


Photo by Brooke Lark on Unsplash

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  • James P

    First off, wonderful blog. Your insight & expertise combined with what another commenter called your superb writer’s tone makes for easy to digest (sorry bad pun 😉 ) reading.

    First question: Perhaps I missed it somewhere, and I’m quite tired (11:33pm EST and been up since 6am) but how would we go about getting our blood serum insulin levels checked? Is there an at-home device like a blood glucose meter or does it have to be done by a blood lab with a MD’s prescription?

    Second question(sorry its a long one): I have recently learned read Gary Taubes books. I began with “Why We Get Fat” and then read “Good Calories, Bad Calories”. Over the last 4 months, with my own body and blood lipid profile labs, I have seen the positive results that come from changing from the Standard American Diet to low-carb diet. My body fat has decreased, my LDL was elevated & now only slightly elevated and my triglycerides are within normal ranges. So would say that I certainly have a good understanding of both the concept and the application of the statement “Carbs drives insulin which drives getting fat”.

    That said, I am concerned about my own mother. She is 61 years old and has metabolic syndrome. She is overweight & has been diagnosed as borderline Type-2 diabetic. She was on metformin, but is now off it and can manage without it via diet (avoiding high GI carbs). She is post-menopausal and is on hormone replacement therapy to alleviate the emotional/mental effects of being post-menopausal. Her blood pressure was high but has resisted the doctor’s attempts at putting her on another drug. She had her gallbladder removed about 13 years ago and has to take nexium for heartburn flare-ups after eating too much fats, most often the culprit is beef fat.

    She has never been a big fan of junk food but had cut out junk (soda, crackers, cookies, chips, icecream) within the past 5 years. She has also read “Why We Get Fat” and for the past 2 months, she has begun following carb-restriction ideas and no longer eats traditional sources of carbs (bread, pasta, grains, fruit, potatoes). Her observation is that she has not seen any amount of on-the-scale body weight change either up or down. Her clothing is not any tighter or looser.

    I am reminded of a certain paragraph in “Good Calories, Bad Calories”.
    "All other hormones will work to release fatty acids from the fat tissue, but the ability of these hormones to accomplish this job is suppressed almost entirely by the effect of insulin and blood sugar. These hormones can mobilize fat from the adipose tissue only when insulin levels are low - during starvation, or when the diet being consumed is lacking in carbohydrates. (If insulin levels are high, that implies that there is plenty of carbohydrate fuel available.) In fact, virtually anything that increases the secretion of insulin will also suppress the secretion of hormones that release fat from the fat tissue."

    So with this knowledge, do you know if Type-2 diabetics have an easier or harder time losing the body fat on a low-carb diet compared to someone who is simply overweight but not insulin resistant? Perhaps I assume too much and perhaps my little knowledge on this topic might be a dangerous thing, but I gather that as a Type-2 diabetic, upon seeing glucose, that her pancreas creates too much insulin (hyperinsulinemia ?). I have no conclusive proof (blood labs, etc.) that would show consistent elevated levels insulin in the blood which would inhibit lypolysis.

    I have to guess that she is eating about 30g carbs per day and probably ranges from 20g/day to 40g/day during an average week. Is it possible that some people had achieve a lypolytic or ketogenic state at about 30g carbs/day but do Type-2 diabetics have to shoot for a lower number? Atkins diet book recommends for Phase 1 induction about 20g/day and I as understand it that person must stay below that to be in ketosis.

    But could it be that even at 30g carbs/day that it is too much carbs because the pancreas puts out too much insulin? I am wondering if it could be that some Type-2 diabetic’s blood serum levels of insulin remain elevated for long periods of time, much longer than that of a normal person, and this results in no body fat loss. Thus they must be even more strict about their carb-restriction.

    Again, thank you for the blog and we all look forward to your work with Mr. Taubes on NuSI.


    • James, to your first question, unfortunately insulin can not be check with a home device the way glucose and ketones can, but it can be easily checked at a lab. I won’t bore you with the reason but it has to do with the chemical technique of quantifying insulin, which is quite difficult, given that it’s a large polypeptide (vs a small molecule like glucose).

      To your second question, it’s really hard to answer a specific question about your mom, but I will say that from both the scientific literature and my personal experience, even the most “brittle” diabetic patient (e.g., one on several medications, plus >100 units/day of insulin) can reverse this trend with steady and consistent carbohydrate removal from their diet. Some folks take longer than others. But remember, insulin is a very short-lived hormone. So what insulin you secrete in response to a given meal is gone later. The question is what insulin response are you generating, and over time this can be reversed.

      To me it always comes back to getting more data. It’s probably worth asking her doctor to do some tests to see if she is improving her insulin resistance, such as HOMA-IR and OGTT.

    • I wanted to share my thoughts on this because in my own past experience with going low-carb (~30 grams carbs/day), after the first couple weeks, I stopped losing weight. I was clueless and angry. I now realize that just as much as my body gets fat from carbs, especially refined ones, I am also sensitive to protein.

      I weigh myself everyday because I want to ensure that I am in ketosis and losing weight (at 330 lbs, it works out to about 1 pound a day loss). Some days, if I eat too much meat, I have actually gained 3 to 5 pounds overnight (sucks!). Whatever part of that is water-versus-fat, I don’t care. Bottom line is that the effect is observable.

      So, I am now making an effort at keeping both my carbs low, but also my protein. Yes, it is annoying because I really don’t yet know what to eat, sometimes, but I muddle through it.

      Remember, though, despite less carbs and less protein, I am enjoying my butter, cream, and my (Julia Child-based) hollandaise sauce over my eggs.

      There is a lot of trial-by-error here. I wish it weren’t, but it is. Please accept my experience as just that, as I don’t mean to pontificate anything, but all I can say is that I am losing weight.

      • jake3_14

        To the poster who observed that excess protein made him gain: the body can convert protein it doesn’t need for enzymes and structural repair to glucose through the process of gluconeogenesis. And we know what happens when the body has excess glucose.

    • greensleeves

      Hi James:

      You can go chat with the post-menopausal in-remission-T2D ladies over on the Atkins forum. As a group they all have your answers (and in fact, some advise against an OTTG and in favor of a HOMA). Here is the collected wisdom they report over there:

      “Is it possible that some people had achieve a lypolytic or ketogenic state at about 30g carbs/day but do Type-2 diabetics have to shoot for a lower number?”

      Yes. Often. Some, even the renowned Dr. Mary Vernon, live on as little as 12 net carbs a day in order to keep their issues in check. This the trade-off for total remission of T2D. But as a result, they eat well with plenty of green leafy veggies and no more drugs of any kind.

      “Atkins diet book recommends for Phase 1 induction about 20g/day and I as understand it that person must stay below that to be in ketosis.”

      This is a misconception. Atkins follows the science (of Dr. Phinney) and argues that most people are in ketosis anywhere below 50 total carbs a day, and the active male may be in ketosis at up to 80 grams a day. Too much bother is placed on ketosis for women. Your mom should focus on finding the net carb level that puts her T2D into remission. And then she should stay there! 🙂

      “But could it be that even at 30g carbs/day that it is too much carbs because the pancreas puts out too much insulin? I am wondering if it could be that some Type-2 diabetic’s blood serum levels of insulin remain elevated for long periods of time, much longer than that of a normal person, and this results in no body fat loss. Thus they must be even more strict about their carb-restriction.”

      Absolutely yes. Totally yes. In fact, weight loss is very slow for post-menopausal women overall. Life and metabolism are different after menopause. Most women are actually poorly educated about the full range of metabolic changes after menopause. It’s a different country, and most doctors who aren’t specialists in post-menopause are also undereducated, frankly. Many will act as if post-menopausal women are suddenly men, but no no no!

      T2D is a triple-whammy. It just is, ‘cuz life ain’t fair. So you just have to keep at it, focus on keeping the net carb level at a place where the T2D stays in remission. Some of the ladies on the Atkins board who were quite ill report it taking up to 18-24 months before their insulin resistance fully disappeared. Some then were able to “up” their carbs – but only to 20 net a day, with the majority coming from veggies.

      Your mom may just want to spot check a couple of days of calories to ensure she’s around 1800-ish, just to ensure the appetite suppression of low-carb is working for her. But after that she shouldn’t worry about calories at all – focus relentlessly on getting off all meds. There are a few women who even after a year still require a bit of metformin, and a couple on the Atkins forum added the lowest dose of Januvia. These are women who were however 300 lbs+ and severely ill with T2D. Still, even this group reports on the Atkins forum that they have markedly improved their health, have normal sugar numbers, and all are below 200 lbs. They also all exercise for the benefits not of weight loss but for blood chemistry improvement.

      The question that rages in this group is “normal weight.” If you’ve been in this group, followed a very strick 12-net-carb Atkins for 2 years or more, you may not reach that pre-menopausal goal weight. You may never be 130 lbs again. You may have to be content at 170.

      It’s a problem that the low-carb community offers very little information for this group of women, even tho’ ironically they may be one of the largest segments on the diet. I do wish more focus was offered overall on women of all ages who live low-carb. Our bodies are different than men’s and we really do have a different experience, esp. after age 30 or 35.

  • Bill

    Neurosurgeon Russell Blaylock has been a very articulate critic of aspartame. A few examples of his arguments:


    Putting aside comparisons with sugar toxicity, I wonder if you find Blaylock’s concerns credible.

    • Hi Bill, yes, I’ve seen much (but not all — there is so much of this work out there) of this work. Certainly there is a chance that Dr. Blaylock’s concerns are valid, but I have yet to see any data to convince me. You probably know by now that I’m pretty dismissive of animal data, and also longitudinal observational data (like the study I present in this post).

      I am not suggesting that Dr. Blaylock is not credible or that he’s out there selling books on the topic just to make a buck. I can’t speak to that, given that I don’t know him personally. I would give him the benefit of the doubt, though, as I do most people, so I am sure he this insight reflects his honest assessment of the data. It’s all a question of individual risk tolerance.
      I still stand behind my assertion 100% that you are better off drinking a Diet Coke than Coke but, as I said, we don’t yet have enough data to “prove” you can drink an unlimited amount of Diet Coke with no harm. It’s a tough one.

      • Barbara Hvilivitzky

        Hi Peter, gee I really hate to see your comment about Dr. Blaylock: “or that he’s just out there selling books on the topic to make a buck.” I don’t think you are intentionally being unkind, Peter, because you’re not that sort of person – but be careful! Once YOU write a book, or make videos, or whatever you decide on, people will say that about you too!!!!!

        I’ve even seen it written about Mr. Taubes for heaven sake – don’t people realize he’s writes for a living! But seriously, there is NOTHING wrong with wanting to make money from one’s expertise, while helping people at the same time.

        Anyway great post, thanks.

        • Barbara, I think you may have missed my point. I wrote (or at least I hope I wrote), that I DO NOT think he’s out there trying to make a buck…though, now you’ve got me worried I was typing too quickly. Completely agree, nothing wrong with making money.

  • Marilyn

    Thanks. Great post! Have you ever noticed that when you sweeten whipped cream with a bit of stevia, the leftover doesn’t collapse and separate in the ‘frig like whipped cream sweetened with sugar? 🙂

    Xylitol has some antibacterial properties:

    • Marilyn, I’ve never made it with sugar (back when I was a sugar-eater I would not have DARED to eat whipped cream)…

    • Laura

      Marilyn, you have LEFT OVERS! Wow.

    • Correct. the mechanism by which Xylitol (toxic to canines)retards dental caries is this: the mouth flora take in the 5-carbon sugar, can’t process, & die off. Xylitol has no effect on the gut flora, BUT sucraclose does. There is a massive die-off of gut bacteria. The gut bacteria make a lot of your neurotransmitters (serotonin) for one, & hormones.

      Peter, u really blew this whole article- it needs to be redone. Just google mercola & sucralose to get the references!

      Other than that, take care & happy swimming!

      • “Peter, u really blew this whole article- it needs to be redone.” Really? I wasn’t writing about gut flora, so I’m a bit confused by your point.

    • Dr Attia. i like u lot. we may be realted- my grandmother was an Attiyeh. But u r really blowing it on Splenda. The name of this article is “What are the side effects of … sugar substitutes.” They have a side effect on flora. In Finland during WWII, there was a shortage of hops, so they started using a 5 carbon wood alcohol sugar. The data came in that they were having fewer cavities. The bacteria causing the cavities ingested the Xylitol, could not digest it & died. A side effect of changing the flora too much is that yeasts can run rampant. Xylitol does not effect the gut flora, where serotonin is made, and is very active in the immune system, b/ sucralose does! This is a side effect of a sweetner. No? http://articles.mercola.com/sites/articles/archive/2000/12/03/sucralose-dangers.aspx

      looking forward to your post on superstarch- the NFL teams have been using it, I understand. Take Care!

      • Fair point, if we believe this side-effect of sucralose is clinically relevant for fat accumulation (which is my implied “side effect”). Your point is taken, though. Thanks for sharing.

    • Joe Marzano

      Blend a few drops of culinary lavender oil or ground dried lavender flowers into your Stevia, Splenda etc, and allow to sit in a jar for the flavors to meld for a few days or longer. Use some in your next batch of whipped cream, or try it in puddings or tapiocas, and try to tell me you have not gone to Heaven. Enjoy!

  • John Pane


  • maXXX poWer

    Thanks Peter for an outstanding blog,,,Gary Taubes turned me on and I’m astounded by the great insight and prose from a true professional in the field. Gary needs all the help he can get in spreading the word.

    • Thanks so much, but it’s safe to say we still need all the help we can get! Thank you for your support.

  • villjamur stefansson

    Great blog write up, I really appreciate the information. I am an admitted Diet Soda addict – I have been living low-carb for over 15 years, but diet soda is a big vice. So these subjects are always personally concerning to me. There was a study that came out last year ago showing diet soda having an effect on kidney cells:
    Clin J Am Soc Nephrol. 2011 Jan;6(1):160-6. Epub 2010 Sep 30.
    Associations of sugar and artificially sweetened soda with albuminuria and kidney function decline in women.
    Lin J, Curhan GC.

    This study alone was enough for me to kick the habit for about 8 months. Have you read anything new on aspartame and kidney function? Because my addiction is back, and I drink a lot of diet soda. Thanks for the great blog!

    • I actually have not read this study, but I will try to check it out when I can climb out from the burial ground of papers I’m drowning in. What was the effect on you when you gave up the habit? What changed?

      • villjamur stefansson

        I really didn’t notice much difference. Initially, I felt like I was dragging because of the lack of caffeine, but that only last 3 weeks or so. I also drank a lot of iced tea to compensate.

    • Eddie

      I too was once “hooked” on diet soda. I have not had one in over 10 years. Here is a substitute I really enjoy, especially appropriate to mention on this thread about non-sugar sweeteners.

      Flavored sparkling water, (Poland Spring is one brand, and there are others,) with stevia (I buy the liquid Whole Foods brand,)is excellent!


      • Hello,

        I would highly recommend “Zevia” soda. It has zero calories, is made with stevia, comes in 12 flavors, and is incredibly good. For what it’s worth, it is also completely natural. You can buy it by the case (one flavor or a variety pack) on Amazon, and other places, I’m sure.

        • brenna

          i believe if you check zevia’s nutrition info you will find that it contains a significant amount of carbs. sadly, it is sweeted with sugar alcohols in addition to the stevia. frowny face.

  • Adam

    another incredibly informative post. thank you much for your efforts.

    i agree with the relative safety of most artificial sweeteners as you laid out… but there seems to be some mounting evidence against Splenda (google: Splenda Duke study).

    and as you know, i am having a great deal of trouble with fat loss despite a near perfect ketogenic diet, and exercise. the latest casualty has been my morning cup of Peets (i get it shipped in from CA!). I tried drinking it black but almost gagged, so i just gave it up completely. Another testament to the side-effects of a ketogenic diet, I find myself not even missing the coffee in the morning, whereas I used to not be able to function without it. Basically, I sleep deeper now and am completely rested when i wake up at 6am. never though that would happen!

    thanks again…

    • Hi Adam, thanks for a great point. If I recall, I think the Duke study was in rats or mice, correct? I’m not suggesting that EVERYTHING studied in rats or mice is not important, but they have to be taken with the proverbial grain of salt. Also, keep in mind the dose response. A lot of the negative effects of things we eat are relative (like carbohydrates!). All that said, I think your approach is completely logical and makes perfect sense. Start changing things around and measuring the outcomes. Keep up the great work.

  • jake3_14

    It’s my understanding that stevia has a long track record (thousands of years) of safe use. So, even though stevia’s technially a sugar substitute, I think it should be considered as separate from wholly synthetic alternatives, e.g., sugar alcohols, aspartame, sucralose. For example, I’ve never heard of any research showing that stevia produces a cephalic insulin response.

    • Jake, the same case can be made for xylitol, which occurs naturally in fruit. However, it’s still important to think about it for 2 reasons: 1) the process of isolation and purification can add toxins, potentially, or otherwise change the composition in a deleterious manner, and 2) lots of natural things are actually harmful (both acutely or chronically), so just because something is natural, does not ensure it is good for you. Fructose may be the best example of this.

      • I agree. I tried stevia for the first time (from Trader Joes) which is in a white powder form. I also wondered about the potential hazards of a natural plant now a highly refined form.

        I have to admit I really am NOT crazy about the taste, as it is both bitter and and sweet; yet, it works well in “stronger” dishes (like Thai beef salad with lime juice and fish sauce). It is okay with whipped cream over blueberries, but it is a different taste.

        I am a little “scared” of the names like xylitol, erithrytol, etc., because they sound so “chemical”. Intellectually, I realize how ridiculous that sounds, but I find that it’s just best for me to avoid all this stuff entirely. I don’t have any sweet tooth now and I don’t want to “toy around” with tempting myself, as I know how easy it can be to start making some of these low-carb recipes and slide back into some bad habits.

      • jake3_14

        “the process of isolation and purification can add toxins, potentially…”

        This statement indicates that, to the best of your knowledge, this problem is still theoretical. Regarding fructose, the problem is in the dose (as you pointed out to another commenter). If people ate fructose in the amounts our paleolithic ancestors did, our livers could handle it quite adequately, and we wouldn’t have an epidemic of NAFLD.

        Since, as you point out, it takes less stevia than sugar to get the same sweetness effect, moderate consumption seems like a third-order (or lower) contributor to appetite and insulin regulation.

        • Eddie

          If you are open to stevia safety-wise, I suggest experimenting with it in different drinks and dishes. With some it combines deliciously, (as with flavored sparkling water, which I mentioned above,) with some it tastes terrible.

          • Eddie, maybe I’ll give it a try, but right now the only thing I like the taste of is xylitol. Sucralose is ok. I don’t really consume much of either, though.

  • Alexandra

    How does one offer to be of assistance with the NuSci project? I thought I saw something on your blog about it, but now I can’t find it.

    I continue to tell anyone who will listen (very few people)about your and GT’s work. I wonder if it will start another flamewar if I share the article from Nature? The fallout from the NY Times article went on for weeks!

    • Alexandra, please send me a personal email/comment in the next month or so as we get closer to it. Hope to be launching in May or so. Thanks so much for your interest in helping. LOTS to do.

      • Alexandra

        Will do!

  • Amadna

    Hi Peter,

    I came across the website sugarstacks a few years ago, and I thought I’d pass it on. The bloggers use sugar cubes to visualize how much sugar is in a given product. http://www.sugarstacks.com/

  • Edmund Brown

    I noticed you left fructose out of the list of sugar sweeteners at the start of the post. Agave nectar is an increasingly popular sweetener and it is almost 100% fructose. It is used to sweeten coconut ice cream that I used to enjoy but now pass-up because of the fructose. Do you have more writing dedicated specifically to addressing fructose? It is my understanding that it doesn’t provoke much of an insulin response, but I assume (I know the old trope about assumptions) you don’t like it in the diet. If so, why are the alcohol sugars any better?

    • Edmund, I’ve written quite a bit about fructose previously. Most of the harm from sugar is actually from the fructose. If you haven’t already, look at the Sugar 101 post (and definitely watch the video). You’ll learn everything you need to know about fructose. As far as sugar alcohols versus fructose, sugar alcohols are typically far less digestible (i.e., GI losses), and don’t undergo the same metabolic pathways, but you’re right, in this case the insulin spike is not the issue.

  • Steve Pehnec

    Dear Peter

    As I’m sure you must be aware, sucrose is 1/2 glucose, 1/2 fructose. It is the glucose that causes the insulin response when sugar is consumed.

    Dextrose is the commercial name for glucose. And Dextrose shows up as a major component in Equal and other “artificial” sweeteners, such as “Stevia in the Raw”. This is BAD NEWS and the reason I do not use such sweeteners.

    I think you should shine some light on this use of dextrose.


    Steve Pehnec

    • Steve, yes fully aware of the 50/50 split in sucrose and 55/45 in HFCS and the “semantic swap” of glucose to dextrose. And you are correct, some commercial brands of non-sugar sweeteners (such as Equal) actually contain dextrose! All the more reason to read the labels. Dextrose is not found (at least in any great amount) in most diet beverages, though.

      • Steve Pehnec

        Thank you!

  • I’ve lost a great deal of weight (50 lbs) being low carb for the last 8 months, however I seem to have stalled with about 10-15 lbs to go. The one thing I have not been able to give up is Diet Pepsi. I drink 3-5 cans a day. Other than that, I’m very nearly zero carb with my diet. Maybe it is what’s stalling me. I feel like a need to have it, and maybe that need is tied to insulin in some Pavlovian way, and that insulin is what’s keeping those few lbs on.

    • Mike, I would definitely suggest you see if you can reduce that (ideally, to near zero). I’ll be very interested in hearing about your results.

  • Thanks! I’ve been looking forward to this post.

  • PK

    Peter – here’s a question and non-scientific observation.

    What is your take on sugar (or artifical sweetener) and “feeling hungry.”

    My experience: I have been off all sugar and non-sugar sweeteners for nearly 5 months. Water & coffee with a dab of heavy cream. Very low-carb diet, in full ketosis at least 5 days a week. NEVER get hunger pangs. Two weeks ago, I “craved” a DIET Dr. Pepper soda. I bought one and drank it.

    For the remainder of the day – I was starving! In and out of the kitchen opening the fridge, etc. My mind & body was under the control of something else, and I didn’t enjoy the feeling at all. Luckily I didn’t snack on anything, but it was a definitely unusual and abnormal day.

    What is your take on that? Can I draw any correlations to that? Or just pure coincidence? I don’t want to experiment with that again, but I will if you suggest it.

    • Awesome question and very conflicting data. Suggests there is probably some truth to this hypothesis, but that (as usual!) individual variation plays a role. I think you’ve already got an idea of which side you may be on, but it’s good to know that you can test it.

      • PK

        What I’m saying basically is – that since going low carb, my between meal cravings for snacks virtually vanished.

        After drinking the diet soda, something screwed with my body, and I became a different person – heavy hunger pangs… urge to snack on something…

        If the artificial sweeteners don’t have an effect on insulin like you suggest – what is causing that feeling of hunger, desire to eat?

        • My comment about non-sugar sweeteners, to be completely accurate, is that many of them do not produce an insulin response in most people. Still likely in some people, with some compounds. On the hunger question, it’s not entirely clear. Hunger is a physiologic response that has not been completely figured out. Certainly possible it’s one of the other hormones (besides insulin) that plays a role, such as leptin. All that said, focus on what matters: YOU have figured out that these things are bad for you. Very important to know.

        • PK

          Thank you!

        • greensleeves

          Again, group experience from the Atkins board – those formerly T2D or borderline report this often. Thus the Atkins community will tell you to just stay away from all sweeteners. And they argue it’s a brain thing – you have been addicted to sugar, and the artificial sweetener revived your brain’s addictive response, with predictable results. 🙂 It’s basically based on Lustig’s remarks at Jumpstart MD.

          Hope this helps.

  • Fred

    For the people thinking of giving up diet pop, I would suggest you do it asap. I used to drink 2-4 cans a day, then one day I decided to just give it up. The results were, I got past a weight loss plateau and I craved sweets a LOT less. I just don’t miss drinking that type of stuff anymore and it will be 3 years in June. I still crave sweets, but definitely a lot less than before.

    BTW, great work Peter. I am surprised with your findings in this post, because I always thought the results of the sweeteners did cause a insulin spike. Good to know now though, but I am not going back to diet soda…I am not going back. 🙂

    • Fred, really glad to hear it. You did some troubleshooting, had a hypothesis, tested it, fixed it. Great example for us all.

  • Christina

    First of all thank you for this great website and the effort you put into helping people. You’re doing amazing work and making a huge difference in people’s lives.

    My experience with Diet Coke is the same as Fred’s, the previous commenter. I would just start having all sorts of craves after drinking it, and definitely be eating more on that day and the one after. Based on that, I do believe there are people (e.g. me) for which aspartame causes that insulin spike.

    On the other hand, there is this fragment in your article which indicates you might be the holder of some piece of information I am missing. You said: “When I work with people who seem to be doing everything “right” but can’t seem to make improvements (e.g., fat loss), I will usually suggest removing all non-sugar substitute sweeteners to test this hypothesis.”

    I think I am doing everything right – I have an average of 20g of carbs per day, between 1 and 1.5g of proteins per kg of weight, rest comes from fat but never ever go above 1800 cal per day (from carbs, fat and protein). I average at about 1600. This might seem very little, but I do weight 53kg and I’ve been getting on with that kind of number for years. A bit of history: I’ve been on low carb for years (no sweets, no pasta, bread, potatoes, etc, in the fruits department just berries and the occasional small orange etc) and I oscillate between 51 and 54kg. Again, this might seem very little, but I’m one of those persons with really thin bones. One year ago I had my body fat percentage measured and it was 28%, so there’s plenty of stuff to shed off.
    Since the start of the new year, I decided to go for the full ketosis… and it sort of worked, in the sense that I lost about 2.5kg, but in the past 10 days I actually gained about 1.2kg back… I do still eat 100g of berries every 10 days or so and have the occasional square of 90% cocoa chocolate (never more than 2 a day)… but other than that I can’t really think of anything else which I eat and contains sugar. Besides the small weight loss, the effects are great, I do feel so much better – no cravings – and most importantly a much much clearer mind (memory and concentration).
    Though, this sort of went away in the past days and I actually felt very hungry (which felt quite surprising) and, as mentioned, gained weight, what else should I be paying attention to?

    • Christina, thanks so much for your comment about the blog. I don’t disagree with you and Fred. Personally, though I don’t drink more than 1 diet coke or diet dr. pepper every 2 weeks or so, I don’t notice the effects many of you have noted. I completely accept that many folks experience them, though, which is why I always come back to the idea of self-experimentation. I like what you’ve done, which is try to tie cause to effect for your eating habits.

      With respect to your question, it’s really tough, if not impossible, for me to troubleshoot this way. For me to provide meaningful guidance (as I do for folks I coach) I need lots of time and data. A question I would ask you is if you are able to confirm the extent to which you are in ketosis (by blood measurement of beta-hydroxybutyrate)? I find this helpful when I want to assess the impact of different foods I eat.

      • Christina

        You’re welcome but again you’re the person who deserves the thank you :).

        Troubleshooting wise, no, no, I wasn’t looking for targeted guidance, it was just a case of me falling down the me-me-Me! well :). And insisted on the details to ensure I communicate properly that I am doing things right.

        I wanted to know if there are general things that might affect fat loss like, for example (I don’t know if these are actually true, I’m just trying to illustrate a point), coffee consumption or having one big meal instead of 3 smaller ones, things of that sort, that you might have noticed in other people.

        About ketosis – I didn’t have any blood tests, I thought I was in it when I stopped having craves and feeling hungry and now I think I am out of it as I have some craves and feel quite hungry at times.

        I followed your advice and looked back on my food journal and have identified few suspects: coffee consumption increase, protein consumption increase (I’ve been on the upper limit lately), I’ll change those and conclude based on what happens. Trial and error, I guess that’s the way.

      • Christina

        I will reply to my own thread, hoping this will benefit some of the readers:
        1) measured ketone levels with Ketostix – I am above 0.8 but less than 1.6 (in g/L).
        2) removed most of the cheese and all coffee from the diet, increased meat consumption, introduced virgin coconut oil and 1 little lettuce with every meal => almost got rid of cravings and obtained GI regularity, better sleep. I blame almost all the problems on cheese, but because I’ve done too much at once, can’t be sure.
        3) I’m retaining lots of water. I do have about 1 teaspoon of salt per day. I tried increasing, but that seemed to make matters worse: felt lightheaded and weak and got really bloated. I still get headaches every now and then. So there’s still stuff to correct in this area. Not sure how, yet.

        On the other hand, no weight loss yet. Actually, I am now one pound heavier since my last post. (On a humorous note, I need to go out of my way to get into some jeans that were ok a month ago). I just hope it’s the water and there’s a way to fix it. Still, I will keep on tweaking on this for another month and decide then.

  • Ben

    Great article, Peter!

    Quick N=1 thought:

    I’ve been off and on ketogenic diets for the better part of 10 years and have found them to be the only consistent way for me to lose fat and keep it off while at the same time feeling great.

    Over the last few years I was finding it harder and harder to enter ketosis and stay there. It was really frustrating bc. I was doing everything exactly as I had done in the past and was being quite diligent about it.

    As a last ditch effort, I cut out Diet Coke from my diet (I had been averaging 1-4 per day) and it turned out to be the magic bullet I was looking for. Entering and maintaining ketosis became as simple as it had been many years ago. It was hard to do at first bc. I really love that stuff!

    In my online research, I have found a number of similar stories on low-carb blogs and the like. In terms of possible causes, the best that I can glean is that:

    1: My insulin or blood sugar was ever so slightly raised by the consistent doses of aspartame…enough to make ketosis harder to enter and maintain.

    2: The relatively large amount of citric acid in in Diet Coke was repeatedly messing with the natural KREBS cycle in my body and preventing the induction of ketosis from taking hold.

    My best guess would be #2. This is firstly because I must defer to the research regarding aspartame (which you have very thoroughly laid out above) and secondly, I have noticed after a few rounds of ketogenic dieting recently that once I have maintained strong ketosis for a few weeks in a row, drinking a Diet Coke from time to time doesn’t seem to throw me out anymore. I just really need to get through those 2-3 weeks of adjustment to ketosis.

    Anyway, just my two cents. Thanks for all of the great posts and please keep them coming!

    • Excellent insight and observations, Ben. Thanks so much for sharing them with us.

  • David

    Pet peeve: if you have 400% more of something, you have 5 times what you started with. Current sugar intake is 4 times the intake compared to the 1970’s; consequently, we have 300% more of it.

    Good blog. enjoy the work you put into writing your entries.

    • If we consumed X in 1970 and we consume 4X today is this not a 400% increase? That is, X times 400% = 4X, right?

      • David is right semantically. The increase is what is additional. We are consuming 400% of what we consumed in 1970, that is not the same as a 400% increase.

        • Jack, David – I stand corrected! I meant to imply that we consume 400% of what we consumed in 1970. Thanks for correcting.

      • David

        sorry – didn’t mean to distract and take away from your excellent blog. But since you responded . . . if we consume 100 of something, and now consume 200 of that thing, our consumption increased by 100%, or 2x. The intake has not increased by 200%, but rather the total intake is now 2x. Continuing with this, if we now consume 400, it’s a 300% increase (not a 400% increase)

        • Hi David,
          I really appreciate your explanation of percent versus “2x”, as I now “get it”!!!

  • Thanks for this terrific post and this terrific blog. I am on a LCHF diet since early September, and have lost 64 lbs, just over halfway to my target weight of 184 (corresponding to BMI of 25). More importantly, I am no longer taking Novolog, Lantus, nor Avandia and am able to get the best bg control in many years with only Metformin.

    One thing I have not given up is artificial sweeteners, though many people continue to encourage me to do so. When possible I use the EZ-Sweetz liquid version of Splenda so I can avoid the carbs in whatever filler they put in the powdered Splenda packs. It never affects my blood sugar no matter when I have it and I don’t know where people get this idea. I do not use the sugar alcohols, though, because they create an er, explosive problem with me.

    Who knows, maybe there will prove to be something wrong with the sweetener, but I find it no more likely than something be proven wrong with any number of things the self-appointed experts who tell me what I shouldn’t eat, are themselves eating.

    • Jack, first off CONGRATULATIONS on some exceptional progress, not just on the fat loss, but on the insulin requirement. I think your instincts are right to try weaning off the artificial sweeteners (rather than substituting the laxatives).

  • Melinda

    Great writing, Peter. I just wanted to chine in that I got over my diet pop “addiction” by switching to club soda. The ice cold fizz was more than half of what I was missing. After about a year, I quit buying even that and didn’t miss it anymore.

    • Melinda, I hear you! My “airplane” beverage has been soda water with lime for about 2 years now, instead of diet coke. Much better.

  • Matt Taylor

    I find that aspartame and sucralose seem to fire up hunger pangs similar to what sugar used to do. Stevia does not seem to be nearly as bad for me, so I try to use it in moderation instead of the others. There are even some decent stevia-flavored soda flavors out there now.

    • Matt, another example of why EVERYONE needs to figure this out for themselves. Glad to hear you’ve been patiently experimenting with it. Keep it up.

  • So I’m connected via Facebook..will my questions be posted on my facebook account?? I guess I’ll find out..

    • I think these comments only show up on the blog. Try posting through FB.

  • PK

    Sort of related question. I do have those Quest protein bars – which use artificial sweeteners (both with or without sugar alcohols).

    My question is – what is the real deal with “net carbs.”

    One bar has 21g of carbs, but 17g of fiber. They claim “net 4g carbs.”

    How is fiber counted as a carb, but then netted out? Does it or does it not affect insulin?

    That’s my magic question. 🙂

    • The calculation attempts to strip out the carbs that don’t really stimulate insulin, such as insoluble fiber or sugar alcohols. It seems to vary a bit across people, so to be “conservative” I just keep total carbs below 40-50 per day which, in reality for me, probably means my “net carbs” are around 20-30 gm/day.

      • PK

        Gotcha – so to be on the safe side, I ought to factor in that top number and not automatically assume the “net” is as trustworthy as it may seem. Better safe (and lower carb) than sorry!

        Thanks again for your extra-active involvement in the comment sections!

  • Cassiel

    Hi Peter! I’ve been reading your blog for awhile, but this is my first time commenting. I always enjoy your posts, and thanks for another great post about this topic — I know there’s a lot of debate ranging about sugars versus sweeteners, and I always like to hear new takes on it. 🙂

    I thought I’d drop in a bit of personal observation here as it might be interesting to some. I switched to a LCHF diet about a year ago, after eating a rather unhealthy diet for almost all my life. (My parents basically weaned me on Coke (normal, not diet) and I had a heck of a sweet tooth and ate junk all the time most of my life. I’m in my mid thirties now, and it’s honestly a wonder I didn’t end up fatter than I was on such an awful diet.)

    About 7 years ago, I randomly developed pulsatile tinnitus in my right ear. It’s tinnitus that sounds in time with your pulse, so it’s a constant dull thudding in your ear. Nobody knew why, so I was told to just put up with it. (Which sucked, for what it’s worth.) When it got worse about 3 years ago, so that it started interfering with my ability to hear normal conversations, a doctor did a CT scan and told me that there was a blood vessel on that side of my head closer to my ear than normal, and that I had probably come to “hear my pulse” through that. (And again, I was told to just put up with it.)

    Just one week after I went LCHF, my tinnitus started to go away. At first it was for about five minutes here or there, but it was the first time I had heard silence AT ALL for six years, so I really noticed it. It was blissful. Over the course of the following week, the silent periods grew longer, until it vanished almost completely. (And that was just one of the many, many health benefits I got from going low carb.)

    What I found interesting, though, was that it would come back at any time that I consumed anything with sugar in it. Only for a few hours, but obviously I noticed it.

    I also found over time that whenever I eat fruit on a regular basis (such as a half an apple a day) or high-carb veggies with a meal (pumpkin, sweet potato, etc) that it will set my tinnitus off as well.

    So I came to the conclusion that my tinnitus is related to how much carb I consume, particularly refined sugar, which is the biggest direct trigger.

    However, the other thing I noticed was that if I consumed things with sweetener in them, the tinnitus also came back, though not as strong, and only from higher doses than sugar. It was quite specific though, and I tested it plenty. Diet sodas with any sort of sweetener would cause it — they are generally designed to be very sweet, just like regular sodas — but putting a very small amount of sweetener in my tea would not.

    I was living in Japan at the time, which uses a wider range of sweeteners in drinks and foods and has a wider range of sweeteners on the shelf, so I tested it with stevia, aspartame, acesulfame-K, sucralose, luo han, erythritol, xylitol, maltitol, and goodness knows what else. Pretty much all of them set off my tinnitus, but again, it needs to be at a higher concentration than sugar — any dose of real sugar will set me off.

    Interestingly for me, erythritol really turned out to be the best of the lot, and I find it pretty hard to set off my tinnitus with it. So I tend to prefer it as my sweetener of choice, when I do choose to use sweetener. (They had an awesome sweetener in Japan that was 99% erythritol with a dash of luo han, it was perfect. Can’t find it anywhere else, which makes me so sad!)

    I don’t really know what any of this means in regards to sugar versus sweeteners, as it’s all a hypothesis for me — supposing that it was the sugar in my diet boosting my blood sugar? insulin? so that I constantly had the tinnitus, then fixing that problem theoretically fixed my tinnitus, but what does that say about sweeteners that aren’t supposed to affect blood sugar or insulin?

    Who really knows, but whatever it may mean, I’m able to use my tinnitus to gauge how well I’m eating. 😉 One thing’s for sure — the tinnitus was so debilitating in my everyday life that I will never, ever go back to a diet with any sugar in it. I can’t tell other people what to do with their lives, but I know firsthand now just how much sugar was ruining my life.

    Cutting sugar out really cut back on cravings for me, too, and has readjusting my “sweet tooth” so that fruit really does taste sweet now, and “normal” junk food tastes sickly sweet and ucky. So I really don’t feel the need to have much sweetness in my diet, beyond some blueberries here and there, and a few salad recipes that have apples or grapes to enhance the overall taste. Even tea is nice with no sweetener! I do like an occasional really sweet cup of chai, though. Thank goodness for erythritol on those days. 😉

    • Cassiel, thank you so much for sharing your experience with me and others. I have not heard of this before. Obviously it’s hard to draw a conclusion we can extrapolate to everyone, it’s pretty clear that you’ve figured out a way to mitigate this condition. What I like most about your story is the journey. Sometimes folks are too reluctant to try experiments on themselves and they are too willing to accept “feeling bad” as way of life. Thanks, again, for sharing.

      • Cassiel

        Thanks for taking the time to reply, Peter! 🙂 I like to share my experiences — I always figure if what I write helps even one person reading it, then I’ve done some good!

        I first started low-carbing via Atkins, for weight loss… but once I realised all the health benefits, I just had to go out there and research as much as I could about it. That’s when I first found Gary Taubes’ books, and low-carb websites and forums, and Paleo communities, and realised how much info there was. And one thing it really taught me was to read, to consider, and then to experiment on myself.

        All the theories and information give you somewhere to start — but your body is the best guide to what’s best for you. So I’ve had a lot of fun testing things over the last year.

        Going low-carb — in particularly, cutting out sugar and gluten — not only cleared up my tinnitus, it completely got rid of severe eczema I’d suffered for 20 years, resolved my constant ongoing gastro problems, got rid of spider veins on my legs, gave me more energy, and allowed me to lose a ton of unwanted weight. And it’s allowed me to finally be able to better manage my lifelong battle with severe depression.

        Once I realised what a difference diet makes, there was absolutely no going back, and I am not sorry in the slightest. The hardest part now is to NOT be too preachy with other people. 😉

        Thanks again for helping to fight the good fight, and keep it up. Know that there’s lots of us out here supporting what you’re doing!

    • Kate

      Cassiel, thanks for this comment. You have me thinking. I have a similar pulsitile tinnitus in my right ear that I developed over a year ago. My experience went like this. Started low carb around six years ago as a last ditch attempt to help with migraines and chronic daily headaches, after having tried every “natural” and pharmaceutical approach to no avail. Low carb resulted in a dramatic improvement, but did not eliminate headaches. I kept trying to improve upon this approach, eventually trending more paleo, more high saturated fat etc, but no further improvements were seen. I then stumbled upon the Perfect Health Diet about a year and a half ago. I was impressed with their discussion of disease processes including Migraines, and decided to try the version of their diet recommended for migraines. For me this meant adding 200 calories of the recommended starches (white rice, taro, sweet potatoes and some others) adding a lot of coconut oil, and taking all the recommended supplements. Very dramatic improvement, indeed near elimination of headaches. A few other pesky problems, like joint pain, went away as well. The only downside was that I developed the aforementioned tinnitus. MIne is not so bad as to affect my hearing, but is annoying none the less. I always assumed it was one or more of the supplements, or the coconut oil, although trial periods of no supplements and or no coconut oil, didn’t seem to make a difference. I don’t do any sugar or sugar substitutes–I guess I am one of the lucky few whose sweet tooth totally atrophied upon going low carb. You do have me wondering, however, if one or more of the “safe starches” I eat might be the offender! I’ll have to experiment.

    • Amy

      Cassiel, I am so glad I came upon your post. I too started suffering from pulsatile tinnitus in my right ear randomly about a year ago. I was inspired by your story and started to eliminate foods and sweetners to find a possible culprit. It turns out that sucralose was the main factor. I hadn’t realized how much of it I was consuming. I am so happy to say that after cutting it out of my diet my pulsatile tinnitus has eased up, and for the first time in months and months I can enjoy silence. It has taken about two months for my body to recover from sucralose, and I am sure it will always be an issue. When I start to hear a whoosh in my ear now I know something had sucralose snuck into it and I don’t touch it again. Anyways, I hope you one day see this because I just wanted to say heartfelt thank you.

    • Colleen Dixon

      Cassiel, thank you so much for your post! I cut out diet sodas (I easily drank 5 diet cokes a day for years and years) and switched to water and my tinnitus of two years nearly disappeared after just a week. I thought surely that must be a fluke, drank several diet cokes one day and by about 4 that afternoon it came back full force. :/ I tried splenda drinks as well thinking it was the aspartame, but no luck, sucralose triggers it too. I came across this blog googling if Stevia caused tinnitus, I was going to try that next. 🙂 As much as I hate to give up diet cokes, you understand what a relief it is to have a moment of silence. I’m just going to have to find something else to satisfy my sweet tooth!

  • Tommy


    When I was at the supermarket I was reading the labels of sugar substitutes and it amazed me that the carboydrates per 100g are the same as for sugar. Which I believe is 100 per 100g?

    So being on a low carb diet, wouldn’t the artificial sweetners have the same effect from a carbohydrate intake perspective?

    • This is where the “net carb” argument comes in, since most do not stimulate an insulin response, so they don’t “act” like carbs in our body. That said, I don’t count net carbs, and aspire to keep all carbs below about 40 gm/day.

      • Peter how many gms of carb do you calculate heavy cream as? The carton says <1 gm per TBS. So do you calculate a cup of cream (your fat shake) 16gms or 8gms?

      • greensleeves

        Why not use net carbs? Dr. Slavin, the world’s expert on fiber, says we should. Insoluble fiber is indigestible, it can’t have any effect on blood sugar – she’s stated that position for the record. Or do you have other strong evidence-based information? Would love to see the URL for that study! Ty.

        • I don’t bother with net carbs because it’s easier for me to keep track of total carbs and it’s a “higher bar” so to speak. In other words, if I keep total carbs below 40-50, I know I’ve kept net carbs far below that.

        • greensleeves

          Ty for that Peter! So you use total carbs simply for ease of accounting and would rather have a little less subtraction than optimal fiber. I hear ya.

  • Thank you for yet another great article, Peter.
    Do you have any thoughts or data on sweeteners used elsewhere that aren’t available in the United States? Sodium cyclamate is approved as a sweetener in over 55 countries, including Canada, though it is banned in the US. I prefer its taste (and lack of an aftertaste) to that of either aspartame or saccharine. In Switzerland we use cyclamate under the brand name Assugrin.

    • James, I am not familiar with these, sorry. It would not surprise me if the same logic held, though. Of course, I can’t speak to the regulatory process outside of the U.S.

    • George Lovelace

      I remember when they banned Cyclamates in the US in 1970. I used one drop in my bowl of cereal and from what I could calculate, I would have to drink 567 sodas daily to be at risk from cancer from Cyclamates. The US continued to allow the sale of Saccharin which became banned in Canada in 1977. Most bans on Saccharin and some on Cyclamates have either been lifted or are under appeal.

  • I just wanted to say this is a great post, very informative. Thank you for the time you spent writing and researching. I’ve shared this post with several people already! Looking forward to the next one 🙂

  • Peter,
    You mention sugar and HFCS and various other sugars, but didn’t mention honey (50% fructose and 50% glucose) and Agave Nectar (in some cases as high as 92% fructose). I mention this because many people are under the impression that natural products are fine for some reason and are even healthy.

    According to Dr. Robert Johnson glucose does not seem to have the same ill effects as fructose. Yes it raises insulin (obviously) but because it doesn’t follow the same metabolic pathway as fructose and so it doesn’t do the kind of damage that fructose has been shown to do. Is my understanding correct?

    On the topic of sugar substitutes, I’ve been using Stevia based products. Of these I like Truvia and NuStevia (The zero carb, version) in terms of taste. Other Stevia products I’ve tried such as SweetLeaf are quite distasteful. The NuStevia is so potent that I need just a sprinkling of it in my tea/coffee. It’s probably about 1/8 tsp if that.

    Coming to the point, I believe stevia has stalled my fat loss progress. I’ve never been a soda drinker but I do prefer my tea/coffee sweetened. I’m been on a low carb diet for the last 6-7 months and introduced Stevia about 2 months into it and have been pretty much the same weight since.

    In order to kick my fat loss into higher gear (I hope) I’ve been on a strict ketogenic diet since the 1st of the month and if I haven’t lost any fat by the 15th then I plan on removing stevia from my diet. My diet (each meal) is about 85% calories from fat with about 100g of protein divided across 3 meals and carbs not exceeding net 20g per day. I feel great physically and mentally but no fat loss yet.

    Just to be clear I count 1gm of carb for each cup of tea/coffee in my daily total carb count. I’d like to lose 35-40 pounds (currently at 20% body fat) bringing my BMI to 23. So it’s not like I’m trying to lose the last 3-5 pounds.

    My blood glucose (starving or 2 hours after a meal doesn’t matter) hovers between 79-83. I haven’t checked insulin and intend to buy the meter and sticks to test blood ketone levels.

    If I were to test my insulin after ingesting stevia, how would I go about it? I mean I realize I need to get my blood test done but what exactly do I tell my doctor and what protocol should I/we follow?

    • Yes, this is a GREAT point about honey and agave. THANK YOU for mentioning it. See my Sugar 101 post for my comments on glucose versus fructose. To quote Lustig, “it’s a numbers game.” Currently, insulin levels can only be tested at a lab. Not possible to check it with a home device, the way glucose or beta-hydroxybutyrate can be checked.

      • Peter, I get that I need to go to a lab to get my insulin test done. But if I wanted to see if me having Stevia stimulates my insulin, how should I go about it? You seem to have done this and so I ask.

        • You’ll need your doctor to order the test (and you’ll need to pay for it). Lab draws a fasting level. You drink/eat what you’re testing. Wait 2 hours, re-check insulin.

  • Debbie C.

    I’ve been enjoying your blog lately. One thing I might mention, for any dog lovers out there, is how *deadly* Xylitol is for dogs, I mean totally toxic. I won’t even have xylitol in my house, but accidentally wound up with some pudding that contained xylitol that sort of fell into my shopping cart. I didn’t want it, but since I found it when I was home I just decided to keep it and try it out. I had one, but it was awful tasting, but I ended up finishing it anyway. Put down the carton and went into the other room, but heard a sound from the kitchen, and there was my dog licking out the carton!

    Knowing its deadly properties I rushed her to the vet for a stomach pump. She turned out to be okay. They said that just licking the carton was probably not going to hurt her. But they did say it was good I’d eaten the whole pudding! Those snack sized puddings are not very big, but as little as 1/2 a small snack-sized pudding would have been enough xylitol to kill a dog the size of mine (45 pounds).

    Needless to say I put the rest of the puddings in the trash when I got home and will be even more stringent about what goes into my shopping cart, either accidentally or on purpose. 😀

  • Traci

    Dr. Attia,

    Is there a protein level that you recommend for a ketogenic state? Is there an amount that would be “too little”? Where you may lose muscle mass?

    • I discuss this in more detail in other posts and comments, but 1 to 2 gm/kg/day is the right zone.

      • David

        Does 1-2 gm/kg/day hold for larger individuals as well? Or should you just try to be closer to 1 gm/kg/day as 2 gm/kg/day could be well over the 150 gm/day you discussed elsewhere.

        • I’m about 77-78 kg, and I do about 1.5 gm/kg/day. One thing to keep in mind, when you are ketotic, you actually require fewer amino acids, as the ketones help preserve them, especially the BCAA.

  • Janknitz

    I rarely eat anything that needs sweetener except for the occasional treat. And I’ve found I dislike all sweeteners. Sucralose has an ammonia aftertaste to me and I’ve learned they use ammonia in processing it. Stevia tastes bitter even the pure stevia that seemed ok to me at first. I don’t like aspartame. Xylitol is ok but I have a dog and it’s highly toxic to dogs.

    I’m thinking about trying small amounts of prune purée (actually baby food) as a sweetener. It would come out to 1 gram of carb per serving with the amount I want to use in a particular recipe. I know the fructose argument, but it’s a VERY small amount. Would this be harmful in small quantities? I sometimes eat a few blueberries or strawberries, very small amounts (5 small strawberries, 20 blueberries) and I don’t see that using the prune purée would have any more impact than that.

    • Janknitz, a limited amount of fructose is ok, depending on how you define “limited.” My preference for fructose-containing foods: raspberries, blackberries, strawberries, in that order. Because I’m in ketosis, I limit myself on days I eat fruit to no more than about 5 or 6 gm. As for baby food, you’ll need to do the math on what’s actually in it.

      • Janknitz

        Thanks, the baby food prune puree I’m looking at is Earth’s Best organic–it contains ONLY prune puree and water. And the entire jar is about 11 net grams of carbs, I would divide that into 10 servings, so it’s pretty negligible.

        Not sure how it’s going to taste, but I’ll give it a try ;o)

      • Lacie

        Rice syrup contains only glucose, not fructose, and is supposed to be less sweet than sugar. I like the taste. I also use it in my homemade ice cream because it gives a better texture and isn’t as sickeningly sweet as ice cream made with table sugar. It’s a pretty good use for heavy cream!

        • Yes, definitely less sweet than fructose and ideally a good way to wean yourself off “the sweet.”

  • Conni

    Peter, count me among your avid fans. Your blog is terrific all by itself, but I’m blown away by your generous responses to comments.

    I’ve been doing low carb/high fat for a year, reached my goal weight in about five months (I lost 23 pounds), and have easily maintained ever since. I have avoided all sweeteners, and usually use no more than one packet of Sweetleaf Stevia per day. One tip I’d like to share that might help someone else – I do eat some 85% dark chocolate nearly every day. When I find that I’m developing a craving for that chocolate, wanting more and more, it is usually a signal that I have slipped into old habits and am not eating enough fat. Adding more fat has, so far, always made those chocolate cravings go away, and it returns to being a nice treat of a couple of squares.

    The question that has been troubling me is whether it is possible to make myself more insulin sensitive by eating fewer carbs than I need to eat. I have found that I can eat between 45 – 60 carbs per day without causing any problems, as long as I don’t eat more than about 20 carbs at one sitting – and even then, it had better be in combination with a hearty dose of fat.

    However, although I can eat those 60 carbs per day, there are many days where I might not eat more than 10. If I do that (eat VLC) for too many days in a row, is it possible that my body will then decide that 45 – 60 carbs a day is now too much, and I won’t be able to do that any more?

    I am so glad to have been led to your site via Gary Taube’s blog. With my unusually slim shape for my age (52), I am now a walking advertisement for low carb, which is causing my friends and family to jump on board. It’s nice to be able send people here to get clear, concise information about this way of life. Thank you for that, and for all you’re doing to get the message out there!


    • Conni, thanks for your kind comments. In general, the more you consistently restrict carbohydrates, the more insulin sensitive your cells become. This implies that subsequent carbohydrate load will actually stimulate less insulin (than prior to carb restriction). I don’t actually know the answer to your real question (which I think is: if I fluctuate between 10 and 60 gm/day, does my body do worse with the 60 than it would have previously?). Two ways to think about this: the 60 gm/day in isolation (relative to a 60 gm/day from your previous eating ways, which would have been a low day), and in “totality.” You are certainly better off in “total” doing 10, 10, 10, 60, than you are doing 100, 100, 100, 60 — so that’s part 2. As for part I, I suspect you’re still better off, but I do not know for sure.

      • Conni

        I think this point is very important, because the greater the variety of vegetables and fruits we can eat and not cause our insulin too soar too high, the better. In fact, it’s an argument that anti-low-carbers use: that we’re setting ourselves up for future problems by actively causing our bodies to be overly insulin resistant.

        If you’re saying that’s true, then it seems it would be rather critical for each of us to find the highest level of carbs we can eat and still lose or maintain our weight, and then keep eating at that level so as not to lose the ability to eat the widest variety of foods possible. I’m concerned about how to guide my family and friends so as not to cause them preventable future harm.

        Thank you so much for your response.


        • Well, I’m saying that’s the case, only that I don’t know the answer. The far bigger issue is the aggregate one — it’s clearly better being in the lower insulin-secreting space.

  • Mike

    Please help! What can one do to control the bad breath that comes with ketosis. My wife can’t take it anymore.

    • Mike, in my experience this goes away after sufficient time in ketosis when you body gets more and more efficient at utilizing the ketones. Timing is variable.

  • Mitt

    I’ve been strictly low-carb for two years now after reading Taubes et al. and finding the argument very persuasive. I’ve also recently discovered this blog and thoroughly enjoy it. I’m grateful to you for making the obviously considerable effort to keep up both your original writing as well as maintaining a dialogue with your readers.

    I’d like to present some objective data about my personal experience with an artificial sweetener and ask a few questions about how you might interpret them.

    BACKGROUND: After an initial weight loss of 30 lbs. during the first few months of low-carb, I’ve been more or less stuck with 120 lbs. left to go. Not surprisingly, this is really frustrating and my eating plan has lost all credibility with my wife and others who say “If low-carb is the key, why isn’t it working for you?” Anyway…my doctor, who is generally positive about low-carb, keeps latching on to one thing and another to try to explain my stalled state. The latest suggested culprit was Diet Coke (by implication, all artificial sweeteners) and the alleged insulin response to the Sucralose etc. I had actually stopped regular consumption of Diet Coke months before, but I still had the occasional large dose 3-5 times per month. So, I was pretty skeptical that this had anything to do with anything and, as a data junkie, I wasn’t all that interested in the bewildering array of merely anecdotal “evidence” out there on the topic. So, I managed to arrange a “glucose” tolerance/insulin level test, but without the glucose. The results surprised and confused me in equal proportions.

    DATA: I was fasted for 8 hours, and my fasting BG was 115 (yes, I’m borderline Type-2) and my insulin level was 32.6! Immediately after the first draw, I slammed down my drink of choice–a 52 oz. QT cup of iced Caffeine-free Diet Coke. It took me 6 minutes to get it down–quite a feat, I have to say. Here are the remaining insulin results: 30 minutes – 41.7; 60 minutes – 32.2; 120 minutes – 23.1.

    Since I obviously couldn’t run the experiment with glucose simultaneously, I have to wonder what those data would have shown. It would have been interesting to compare. Maybe glucose would have caused a 300% rise in insulin–who knows? That would at least have given some sense of proportion to the rise caused by the Diet Coke. Guess I’ll have to wait on that one.

    While my doctor found the test results interesting, she interpreted them straightforwardly as support for her Diet Coke theory but had little else to offer and, naturally, had no time to really thoroughly discuss the implications of the results.


    1) First, after 2+ years of seeing several doctors including endocrinologists, who all obsessed about making sure my BG didn’t get too high (it’s under pretty tight control with A1C at 5.3), no one ever suggested testing my insulin levels. I was pretty dismayed when I saw the 32.6. From what I have read, 2-10 is a normal healthy fasting insulin level. If insulin is so short-lived in the system, what might explain such an elevated FASTING level? Could this piece in and of itself hold a key to understanding long term non-weight loss?

    2) Given the high starting point and the transience of the effect (gone at the 60-minute mark), is it likely that the 9.1 point increase (+28%) after consuming the Diet Coke would have any significant effect on fat retention, assuming, of course, that one wasn’t consuming this quantity of Diet Coke every hour or two?

    3) I understand the notion of cephalic response–really no more mystifying than one’s mouth watering when thinking about or seeing tasty food. But, if the analogy holds, one’s mouth doesn’t go on watering long-term (Homer Simpson being an exceptional case, I suppose). In this instance, I was certainly not excitedly anticipating the taste of the Diet Coke and forcing that amount down in six minutes was anything but an enjoyable taste experience. So, has anyone actually measured the magnitude of cephalic response, which I’m sure varies widely? Are there any data out there indicating how much this seemingly transient effect might actually matter in terms of overall body fat regulation?

    Note: In support of the anti-artificial sweetener position, my doctor cited a study that found that the small intestine has taste receptor cells similar to the tongue’s that are sensitive to sweetness. The implication was that artificial sweeteners could trigger these and contribute to the cephalic response. (If it’s true, I guess we can be grateful that it functions unconsciously as the idea of tasting the contents…well, you get the idea). I read the study and didn’t find it all that compelling, but what do I know? Are you familiar with this study or with this theory?

    I apologize for the long posting. I hope that the objective test results showing that Sucralose did, indeed, seem to cause an increase in insulin level will be of general interest and I would definitely appreciate any insight you can share regarding the issues in the questions I’ve raised. Thanks.

    • Hi Mitt, thanks for your questions and appreciation for the blog. Unfortunately, I can’t respond completely to questions of this nature on a blog for several reasons, perhaps the most important being the legal one (I’m not permitted to practice medicine via a blog). Hopefully the information in the blog and in other references can help answer your personal questions. It is clear, by calculating your HOMA-IR, that you are insulin resistant. It’s great that you were able to gather such data and I sure wish more doctors were willing to do this sort of work to really get at the individual level of what’s going on. Your doctor was wise to do this test. There are folks (like me) who do not appear to have much of an acute insulin response to sugar substitutes. What I don’t know is if there is a more long-term impact on insulin sensitivity from these substances.

      As for your question about the cephalic insulin response, it’s not actually clear (to me, at least) what is mediating the trigger or the duration. I’ve seen papers suggesting parasympathetic mediators (i.e., the same transmitters involved in saliva secretion). In fact, I just read a paper from PNAS suggesting that other (non-glucose) circulating nutrients can stimulate the beta-cell and potentiate the glucose-triggered response of insulin. Clearly “we” don’t know enough to provide definitive guidance. When in doubt, though, cut it out.

    • Scott R

      Its worth noting that distension of the gut also causes secretion of insulin. So drinking such a large amount of Diet Coke might have been sufficient to prompt an insulin response through this mechanism, despite aspartame’s (probably) negligible affect on insulin levels.

      This should also be applied more broadly when considering your diet. If you consume large meals, even of seemingly innocuous foods, the quantity might spike a disproportionate insulin response. I seem to recall Dr. Bernstein stating that you can feed a diabetic rocks and still get an insulin response.

      • Scott, I’m not sure this is true in general. Obviously, anything can be true for some folks. Gastric distention may cause some component of satiety, though not insulin secretion in most.

  • Kristin STL


    Is it wheat or sugar that is killing us? I would love a commentary on this subject from you or Gary Taubes. I read “Wheat Belly” by Dr. Davis and then listened to dr. Lustwig’s lecture on sugar. Seems there is some contradictory messages out in the low carb world. Perhaps you could help enlighten?

    Although dr davis’s “wheat belly” lacked the scientific rigor that dr lustwig applied it appears to be very popular in the mainstream.

    • Kristin STL

      Please excuse my typo. I meant no disrespect for the venerable dr LUSTIG

    • Kristin, they are both right. Wheat and fructose are both killing us slowly. Take a look at my commentary in the second part of my Sugar 101 post.

  • Aaron

    Hi Peter, Thank you for taking the time to make this wonderful website! It’s very informative and easy to read. Just wondering, what advice do you have on organic vs non organic meat? grass fed vs. grain fed beef? I would like to eat more organic but the cost is prohibitive. Is it worth it? Also, do you believe that consumption of animal products contributes to global warming? I’ve heard both sides on this issue and am wondering where you stand on this. Thanks again for your work!

    • Aaron, all things equal, I would prefer grass fed meat over grain fed meat because of the increased omega-3 over omega-6, but there is an economic difference. If it’s “worth it” is a personal decision that depends on other competing priorities. It’s probably not worth it if paying rent is tough. I don’t know enough about the last issue you’ve asked about to have a credible opinion (yet, at least).

  • Marilyn

    I’m not Peter, but I can’t resist. Are all these meat animals contributing to global warming?

    The January 1, 2010 inventory of cattle and calves [was] at 93.7 million


    In the early 1800s, there were 30-60 million buffalo roaming around (to say nothing of untold numbers of deer and antelope).


    If the effects of all those critters in the early 1800s didn’t bring the ecosystem crashing down, I doubt there’s going to be a problem today. 🙂

    P.S. I’m old enough to remember Global Cooling, which was blamed on many of the same things Global Warming is now. TMTCTMTSTS

    • Aaron

      Interesting links, thanks Marilyn. As I understand it, the problem it has more to do with the nature of industrialized agriculture than the number of animals being raised. How our eating choices impact the environment is an important topic worth exploring. (Though not completely related to Peter’s work).

  • On 2/8/12 James P wrote:

    I am concerned about my own mother. She is 61 years old and has metabolic syndrome. She is overweight & has been diagnosed as borderline Type-2 diabetic. She has also read “Why We Get Fat” and for the past 2 months, she has begun following carb-restriction ideas and no longer eats traditional sources of carbs. Her observation is that she has not seen any amount of on-the-scale body weight change either up or down. Her clothing is not any tighter or looser.
    James, that’s because your mother probably doesn’t have Metabolic Syndrome. She probably has Metabolic Syndrome XX (MSXX). From my comments on Chris Masterjohn’s blog —
    It was after reviewing their blood tests over and over again that I realized I was seeing a pattern, and one that had left them undiagnosed for insulin resistance/Metabolic Syndrome for years, despite the fat gain and complaints. We who have MSXX do not fit the MS category — at all. We have high HDL and low TG. We have normal blood pressure. We have normal TSH, and rising but still normal A1c and fasting insulin (most of the time; hyperinsulinemia is seen in 100% of women who took HCG injections). Yet we are fat. We are tired. We are cold and we often offered tranquilizers for our clearly deluded minds.

    In MSXX however, the symptoms are quite different from those in MS. With MSXX, the particular flavor of IR is PCOS, regardless of age, regardless of menstrual regularity or ability to get pregnant. Unschooled doctors often insist that PCOS isn’t there when it is. Insulin levels are usually normal, but insulin in MSXX is bone-ass lazy. It just can’t do the job. Thus, 1-hr PP’s are often lower than 2-hr PP’s – a major MSXX symptom.

    Gluconeogenesis is out of control. We are exquisitely sensitive to Cortisol. As a result, when *we* do “Body By Science” workouts, we may put on muscle — but we *always* put on fat around the middle. Impossible, but true. The slightest amount of excess protein sends sugars way up, despite eating no carbs but veggies. Reverse T3 is enormous. Free T3 and Free T4 are in the basement. Temps are incredibly low, and energy is negligible. It’s very difficult for women with MSXX to achieve lipolysis, despite very low calories and carbs. One symptom of untreated MSXX is water loss and gain of the same 2 – 5 pounds, over and over and over again.

    The Protocol treats and reverses all that. All of it. Although for the most resistant cases, Metformin is necessary. In fact, in helping so many women with it, I finally had to ask myself if female obesity and male obesity are somehow different. My answer now is: Yes. This helps explain why so many women follow Taubes, Groves, Lutz, and Attia to no avail. What those men, who I greatly respect, know most about is male obesity, and their advice seems to work wonderfully for men. For women, it’s hit or miss. For women with MSXX, it’s always miss. Especially if they go VLC for an extended period, which invariably shuts down their metabolisms with massive thyroid hormone problems.
    James, I hope you and your mom read the full comments, and then go to the blog to read the Protocol Participants journals to see if they fit your mom’s parameters. I bet they do. If so, the Protocol can help her.

  • Somehow the link to Chris Masterjohn’s blog got deleted from my post above. It is:


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  • Kenny

    Peter, thanks for pointing out what I intuitively figured out when I started low carbing years ago. That drinking Diet Coke was better than Coke. It was hard for anyone I told this to believe. So good to hear you agree. These days I also go for a Diet Dr Pepper once a week or so, but otherwise all my drinks are unsweetened, natural or not.

  • Bob

    On the subject of insulin, after reading Gary Taube’s books and closely examining my own eating habits, I believe it is likely exercise does not cause weight loss due calories burnt. That is, I eat more on the days I exercise. What about exercise and insulin? Have you performed any research on insulin sensitivity and insulin? Taubes seems to think exercise does not affect insulin sensitivity, but the minimal amount of research I’ve done implies otherwise. Of course, after reading the many books I’ve read on cholesterol, low carb, etc., I’ve learned one can’t really trust research without detailed study.

    My wife has been trying low carb, and it’s helped her, but she’s not lost a lot of weight. I’ve counseled her to stop using artificial sweeteners as a test. We’ll see what happens.

    • Bob, this is a great question, and your observation is reflected in the data. The calories one expends while exercises tend to be matched by increased caloric intake. The second order effect of exercise is to increase insulin sensitivity, primarily of myocytes. So in that sense, it seems exercise could have a real impact on reducing IR. So why don’t we see a significant difference? It’s a great question, but I suspect the reason is that the effect does not last very long (relative to the length of time we’re not exercising).

  • Bob wrote: “My wife has been trying low carb, and it’s helped her, but she’s not lost a lot of weight. I’ve counseled her to stop using artificial sweeteners as a test.”

    Bob, if your wife has ‘tried’ low carb but has not lost significant weight, it is likely that she has the insulin resistant form of PCOS. In this case it’s not that her cells are terribly resistant to insulin’s message (they are to a degree or she would not have put on excess fat), but rather that her insulin is not very efficient. It’s lazy, in fact, and not up to the job of dealing even with the few carbohydrates she is eating. Artificial sweeteners (unless she’s using a glycerin form of Stevia, for instance) would not be the culprit here.

    If it is PCOS, exercise will only make things worse. Peter asks: “The second order effect of exercise is to increase insulin sensitivity, primarily of myocytes. So in that sense, it seems exercise could have a real impact on reducing IR. So why don’t we see a significant difference?”

    Because exercise also increases cortisol, which depresses insulin, thus increasing blood sugars. Women with PCOS are very sensitive to cortisol. The women participating in the Protocol on my blog have discovered that even using a bit of corticosteroid creams for a skin problem raises their otherwise normal blood sugars — a lot! If they stop using the cream, sugars return to normal.

    One size does not fit all, not even low carb diets or exercise that works well for men in general and women who don’t have PCOS.

    Bob, have your wife come to sugarfreegoodies.wordpress.com to review Participant’s journals and diets. If she emulates them, she will lose weight and especially fat around the middle. She will become insulin sensitive again as her insulin gets the kick in the pants it needs to handle glucose more efficiently. No exercise required. 🙂


  • Peter, I enjoyed your post and especially the followup questions from other posters. I was reminded of a caution about caffeine from my Atkins days and found this article: http://care.diabetesjournals.org/content/25/2/399.full. Basically, caffeine is believed to lead to reduced insulin sensitivity. If you add that to study results of diet soda, it is easy to see how sugar substitutes could be mis-attributed to negative health outcomes. It should be noted that the effects of caffeine on insulin sensitivity were seen at levels of 5-7 cups of coffee per day. But I take from this that individuals who may already be insulin resistant, should avoid caffiene, with or without sweeteners. With thanks, Louisa

    • Louisa, yes this is a very interesting topic and I’ve just started following it. Not quite sure what to make of it, but I need to do some serious homework! It’s going on the list, for sure. Thanks for passing along.

    • Scott

      I think its worth noting that we should be cautious when looking at studies discussing “insulin sensitivity,” because insulin sensitivity is not always the objective. Insulin sensitivity is only desirable when our bodies have excess glucose that needs be removed from the blood (generally into our bodily tissues.) Insulin resistance is bad in T2D because their insulin resistance is coupled with elevated blood sugar levels, which are toxic. Muscle insulin sensitivity is viewed as a good thing primarily because it means our blood glucose will be stored in muscle rather than converted to fat.

      But in the context of a low-carb or ketogenic diet (no excess blood glucose), insulin resistance can be beneficial. Insulin resistance on our fat cells means that our bodies will not accumulate excess fat. In fact adipocyte insulin resistance is a natural physiological response to ketosis. There are some very interesting studies involving FIRKO (Fat Insulin Receptor Knock Out) mice on this topic that demonstrate adipocyte insulin resistance as being beneficial.

      So looking at this study in terms of a keto diet, most of the effects listed as consequences of caffeine consumption are desirable. That being said, this seems to have implications for T2D patients who are NOT on a carb restricted diet and are instead relying on insulin injections, as the loss of insulin sensitivity would exacerbate their inability to manage their blood glucose.

      • Leoni

        Scott, very interesting, thanks for posting this.

        It’s good to read a counter-argument to the whole “A VLC or Zero Carb diet will give you Insulin Resistance!!!” that I seem to constantly stumble upon being touted on the internet as something to be gravely feared (along with, “Long-term ketogenic diets will ruin your Thyroid!!!”).

        Occasionally these ‘dire’ warnings by so many general Low Carb ‘experts’ does cause some angst for me I must admit!

        So I appreciate being presented with a different contextual perspective to consider.
        What you wrote seems reasonable to me so I find myself greatly cheered and reassured! 🙂

  • Debbie

    I treat myself in the evening – after my 3 ounces or so of nuts – to about 4 hard candies made with rice syrup. For years I’d been eating bags of sugar-free candies; I have given that up, but want to hang on to something. The rice-syrup candies are much less sweet tasting than the sugar-free type – hence, I’m thinking they’re better for me. Are you saying artificially sweetened might be healthier?

    • Certainly possible, depending on your reaction to them.

  • Hi Peter, it looks like the site is starting to take off by the amount of comments here. A quick question: you said you’ve tested 3 of the sugar substitutes on yourself (xylitol, aspertame, and stevia – I think) and you’ve found that they DO NOT increase your body’s production of insulin. In other words, your sugar does not increase, correct? How do you test that? Is it as simple as testing your blood sugar pre sugar substitute drink, then post sugar substitute drink with a blood sugar meter/tester at home?

    Thanks, keep up the good work.

    • I did it at a lab where an hour after consuming the sugar substitutes I had my blood levels of insulin and glucose tested. This is probably overkill for most folks, though. A home glucose meter is good, or just noticing how you body responses with and without sugar substitutes in your diet over a period of a few weeks.

  • Peter,
    This is an update to my previous comment here. I haven’t testing my insulin response to Stevia or other substitutes but I did stop them completely and didn’t get over my weight loss plateau.

    Next I tried Intermittent fasting, and wham! I lost 11 lbs in 11 days and 1.5 inches around my waist. I believe being ketogenic or keto-adapted ( beta-hydroxybutyrate levels of 2.5-4.5 mM) makes IF really painless.

    I do a 24 hour fast (my wife does a 16 hour fast), and I work out on the days I fast, right at the end of my fast. Here is how I do it:

    I’ll eat lunch one day and skip dinner and then next day’s breakfast (my wife will eat breakfast). I’ll work out just before lunch for a good 1 hour or so. I feel no difference in energy levels during my workout. In fact even after my workout I don’t really have any hunger. I do eat lunch and dinner that day, mainly because I should because it is important for the whole IF thing to continue working.

    I’ll eat breakfast and lunch the next day and fast again as described above.

    During fasting, one can drink water and other non-caloric beverages. I just drink water and for dinner (on the day I’m fasting) I’ll have a cup of bullion.

    I do plan to get my insulin response to Stevia tested, just to be sure…

  • Fay

    Hi Peter, I found your website via Gary Taubes’ one. I use Diet Pepsi to get rid of indigestion. I’m a Type 2 and in the UK it’s impossible to get indigestion remedies which are sugar free. I sip Diet Pepsi slowly, I belch, the excess gas goes and no more indigestion :)Diet Pepsi makes no difference to my blood glucose whatsoever whereas indigestion remedies such as Rennies make my blood glucose spike.

  • lorraine

    I haven’t yet read your “pet peeves” post but this is certainly one of mine – how the media bumper stickers these studies. I feel like I spend half my working life providing the more thorough analysis of these reported studies. I can almost (I said almost, not actually) forgive the research because well-controlled prospective studies are so expensive, but the press releases of these studies are such junk and they typically come from the department that did the research.

    A quick question, albeit a bit off topic, because you seem like the guy who would know, there aren’t any home insulin testing devices for post-prandial insulin, are there? I’ve not ever found one. Nor have I found blood spot post-prandial insulin tests (like with a blood spot fasting insulin or A1c)that you can just mail in. Is there anything short of going in for a glucose challenge (or xylitol, aspartame etc.) to determine post-prandial insulin?

    I’m still intending to plug your results from your glucose challenge (per your JumpstartMD presentation) into the HOMA-IR to see if it would have predicted your insulin resistance, give this is the main metric that clinicians and research studies use to determine it. I just have to go back and find that part of your presentation, but I have my suspicions it might have missed yours (and therefore, possibly many other people).

    • I already calculated it for you. Check the 3rd part of my personal journey. There are no convenient tests for insulin because of the radioimmunoassay required. Because insulin is a such a large polypeptide, you need to do ELISA to get it to work. I’m hopeful, though, one day we can do better than going to the lab.

    • lorraine

      Ah yes, so you did do that calculation. Those posts looked similar to the lecture so I skipped them, and did not see the HOMA-IR in the vids. Good news, tho, that it did correctly predict. I thought it might be too close to call given your age and fitness vs the standard used to calculate the constant.

      • The reason I like HOMA-IR and OGTT to get both an objective test (HOMA) and a more subjective view. My OGTT is interesting for normal glucose on both counts (which is what most folks pay attention to), but look how high that insulin went to keep it there! OGTT is a great 2-for-1 study.

    • lorraine

      “look how high that insulin had to go”……..Exactly! Pretty mind blowing for me, frankly. When I first looked at your pre-VO2max test, I coukdn’t wrap my brain around that 60% VO2 peak, which is why I asked under a different post (before I had more familiarized myself with your self data) how trained you were at that test. That R at that level looked almost untrained to me, but now from the glucose tolerance challenge, you can see why that R – you couldn’t get to your fat! That really stopped me in my tracks, both for exercisers/athletes everywhere out there slogging it out, and also as an eye opener regarding what training may not do for improving IR.

      • Exactly! And remember I was fit! I could hold 60% VO2 for 12 hours without stopping, but I needed SO much glucose to do it — I’d make myself sick (literally) just to keep going. So glad you saw and appreciated this very important point.

  • lorraine

    Yeah, I did wonder how much it hurt back in the IR days. Man, you would think that if anybody would reap the benefits of training effect on insulin sensitivity it would be someone training at your level (ok, factoring out the potential cortisol effect), so of course, the question becomes, how much benefit does training alone actually confer? For all of us in those maturing years and more prone to IR, it’s really something to think about as a factor in lower performance and harder recoveries.

    • It probably varies by person. I was shocked how metabolically unfit I was, despite CV fitness. Bad genes, I guess. HDL-C was 31 and TG >150, so you know I wasn’t born lucky.

    • lorraine

      So not to belabor the point, and I really appreciate your time here in the comments, but it struck me that the IR basically robbed you of *all* the expected training effect, at least on the (a – v)O2 side. Like you said, you probably derived benefit from all your training on the cardiac output side, but after all those years training, you show up for a GXT and look metabolically untrained. That’s just crazy, and requires real rethinking for me when discussing exercise with diabetic and metabolic syndrome patients. I mean, of course it’s common knowledge that IR makes it difficult to access ffa’s, and I see HOMA-IR’s (and HDL’s and TG’s) way worse than yours, so my assumption was kind of in the realm of a little IR, a little trouble with getting at fat. But a basically complete lock out at modest exercise intensity at your HOMA-IR was a real paradigm shifter for me…..love when that happens!

  • So being that it was the weekend of chocolate just gone, we tried to get our kids ‘no sugar added’ chocolate eggs from Thorntons here in the UK. Thorntons are pretty good quality chocolate manufacturers so we thought it might have been the best option to reduce the sugar the kids were having and at the same time trying not to be the horrible parents by denying the kids the good stuff.

    These were advertised as being recommended for diabetics as they contained no added sugar… except for the ‘naturally occurring sugars’ (8g per 100g). Anyhow, they instead used Maltitol as their sugar substitute. It wasn’t until I got them home and checked out Maltitol and its benefits/disadvantages. Little did I know at the time that Maltitol appears to be the worst sugar substitute you can buy and apparently has almost the same effect as having actual sugar.

    Looking at a GI chart for sugar and the available sugar alcohol substitutes, apparently sugar has a GI of 60 and Maltitol has a GI of 52, according to the source I was reviewing. Xylitol has a GI of 13 according to this chart.

    I decided to try it and see what effect it would have on my ketone count. Looks like it didn’t have a good effect on them at all with the test strips saying I am at the very bottom of the scale where I am usually at the top. Not a very scientific study mind you, but interesting. Generally I don’t have any sugar in my diet and my carb count on a daily basis is usually under 20g.

    So for me at least I will be avoiding Maltitol if I am looking at ‘no added sugar’ treats… which is pretty rare anyhow.

    • Good to note. I was looking at some sugar-free dark chocolate the other day in Trader Joe’s, which was made with malitol. I’ll have to do the experiment for myself, too. I assume you controlled for everything else that day (exercise, rest, all food)?

    • Alexandra M

      “…I am at the very bottom of the scale where I am usually at the top.”

      I understand that if you haven’t fasted for 12 hours before using the Ketostix what you may be seeing is ingested fat in the urine. Am I wrong? The only time I turned them really dark was when I was not fasting. Fasting, the best I’ve ever done is 10mg/dl.

    • Peter,

      Not hugely controlled, but I am a bit of a pattern eater so other than the chocolate there was not much else going on that was different. Happy to experiment more tightly though as I am interested in getting a better handle on it. At the moment I would consider this loose basis. Having said that my daily routine is pretty well consistent, but definitely not 100% perfect from day to day. My ketone strip on the other hand rarely changes much and this would have to be the biggest change I have seen since I started testing around three weeks ago. I am currently in the middle of my eight week on HFLC.

      If you wanted to outline how I could control the experiment better, I would love to provide some more solid individual data.

      Alexandra, I always test myself after exercise in the morning and have it pretty consistent. My last meal was dinner the previous evening. No idea if this presents the best scenario for the test though. Happy for feedback if I should be doing it different though.

  • Cindy C.

    Thanks for all of your great work. I started low carb/moderate protein/high saturated fat 3 years ago. Saw so many benefits, but one thing that was most notable was I went from having social anxiety nearly all my life, to now being much more outgoing, and can look people in the eye, and give public talks without being so nervous. This is the site where I started out with the diet.


    Although I do a lot of research, and study on ketosis and low carb on other sites(I appreciate the ones you linked to), I still follow this diet Bee uses. It is ketogenic, and looks to be more healing to the body as a whole. She has a yahoo group as well. It is also done gradually to eliminate carbs, and increase fat. I did not have too many bad detox reactions.

    I did want to mention, I started using aspertame back in the 1980s when I cut down on sugar, and only drank one or two a day. It did not seem to bother me, but eventually, saw signs of its toxic nature. I started having dizzy spells, and really bad brain fog. I also got chronic pain. I did read Dr Blaylock book on aspertame and MSG. My dizzy spells and bad brain fog went away after stopping the aspertame. I read other reports on chronic pain that such increase pain receptors in the brain. The chronic pain, however did not go away until I went ketogenic. I was always thin, but started gaining weight in my 40s, not sure if I just got more insulin resistant, or the aspertame. I did lose some weight after giving up the aspertame, and went back to having a regular soda once a day. I did lose about 20 pounds more going lc/hf. I am 5 feet, slim build, and now 95 pounds. I do not exercise much, but my job and the stairs at home and work keep me pretty active, and I go for walks. I still cannot lift a lot though, and still have some healing to do with my back muscles. I have some arthritis in my spine, and herniated discs in my neck, but I do not blame them for my pain. My former diet and toxins caused the pain. Here is an article related to chronic pain and excitatory proteins.(MSG/aspertame)


    Actually, a ketogenic diet quiets those proteins and increases Gaba.


    Even if someone, especially women, do not gain weight with sugar, they are still at risk.


    Not sure is anyone else read this


    I love doing research. I did not go to college, but took biology 1 and 2 and chemistry in high school-that was 40 years ago. In 1970 I won the Bausch and Lomb Honorary Science Award medal. Some one gave me an Organic Chemistry book this year. It has been helpful.

    Thanks again for a great site, and your knowledge and insight.

    • Thanks for sharing your experience, Cindy!

  • Oly

    Any ideas about why aspartame products raise my blood pressure? It’s pretty healthy to begin with so it doesn’t put it in the danger range. I’m no longer pregnant, but say pre-diet coke it’s 100/70 and post it’s 120/80. But it bugs me because I feel the change. Not enough protein and I’m uptaking and metabolizing it?
    I used to drink diet drinks all the time but one day I decided they were disgusting and quit them. Now when I try to enjoy one, I feel my wedding band get tight. Also had some sinus pressure and shortly after sipping on DC I got a horrible headache.
    Meanwhile, I avoid aspartame big time…saccharine has been around since the late 1800’s so that’s my choice or sucralose or stevia. Or no sweetener of course.

    • Not sure. Try an experiment with carbonated water, then caffeine-free diet coke, then a non-carbonated drink like Diet Snapple, then other sweeteners, etc. Curious if it’s the carbonation, the caffeine, the aspartame, something else?

  • Excellent post! I found my cravings got worse with artificial sweeteners, but I know people who seem to do okay with them. What I read says artifcial sweeteners are 200-600x sweeter than table sugar, and as you pointed out, that’s a sort of expectation of injested calories for the brain; so, for many of us IR folks that turns to big cravings for more sweet. Now that I limit such sweeteners to no more than once a week, I’ve lost those cravings. Here’s the clue: If you drink lots diet soda and/or ea many artif-sweet diet foods in quantities like you did sugary things, you’ve got a problem.

  • Oly

    diet rite & la croix don’t have the same effect.
    I want to say I had an issue with diet jello stuff; I recall throwing my stash out.

    I’m a long time low carber (no ketosis while pregnant, they tested me and said I’d retard my baby *sigh* ) — drank DC for years then just increasingly lost my appetite. The theory I’m leaning towards is it has something to do with fasting…once upon a time I *always* had breakfast with snacks or small meals setup for the day but no longer; I spontaneously fast or go through periods of snacking. So I’m wondering if there’s something about metabolizing that particular amino that’s disrupting or causing too much of something. I was hoping someone already knew…if it’s a symptom I’m depriving myself of protein or…???. It’s not a big deal, I mean I know I feel better without it, right? Just the nerd part of me is curious about the mechanism, the *why* of it.

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  • I think the message is getting out about sugar slowly. The latest article about HFCS.


    Very Interested to see the BBC programme on this also.

    • Watched the BBC documentary on Sugar last night. It was the first in the series (3 parts). It is actually produced by Jamie Oliver’s production company.

      Really good start to the series. It was almost like watching Gary Taubes, yourself and Robert Lustig doing a talk. Gary and Lustig were both interviewed and the history of sugar was laid out in all its horrible glory.

      This is the first time I have seen a documentary from the BBC that spoke about the alternative theory and not conventional wisdom. I am seriously looking forward to the rest of the programmes now.

      If you can view this, definitely take a look. Very exciting to see OUR message getting out on such a powerful network as the BBC.

  • Kitty

    Hey Peter, I had consumed aspartame in rather large amounts for a quite a long time, until I swapped to natvia (erythritol and stevia reb A). Its supposedly better for your health, but because erythritol is a sugar alcohol, I wonder about how the digestion of that and other sugar alcohols is for your liver in the long term. Would they have similar effects to that of ethanol in drinking alcohol? Or will they be harmless. And do sugar alcohols happen to affect blood urea? Ever since I have consumed aspartame, sugar alcohols, and stevia I have had slightly elevated urea, despite normal creatinine. Not sure if there is a link and Ive tried to do some research and havent gotten clear answers.

    thanks heaps

    • The differences are probably most related to the quantity. I don’t think most people who are using alcohol sugars as sugar substitutes consume a fraction of what someone consumes while drinking enough ethanol to induce fatty liver disease. However, as we see ample evidence of non-alcoholic fatty liver disease driven by fructose, it suggests eating TOO much alcohol sugar could have undesirable consequences.

  • Mike A.

    Dr. Attia,
    What would you advise to someone who wanted to test whether they had an insulin response to a particular artificial sweetener? My thought is to check my blood glucose level after fasting, then drink a glass of water that has been heavily sweetened with sucralose (more than I would typically consume), and then to check my glucose level at an appropriate time afterwards. Since I don’t think it is easy to check insulin levels from home, my thought is if my blood glucose level goes down significantly, I must have had an insulin response. My specific questions… Is this the right approach? When after ingesting the sucralose is the best time to check (or the range of time)? What would be a significant enough drop in glucose levels to determine that an insulin response had occurred?

    Thank you for any insights you provide,


    • The only real way to do it is too serially measure insulin levels before and after consumption. Using glucose a very weak proxy.

  • Murray Stromberg, MD

    Dr. Attia; you may want to review an article in the International Health Newsletter, edited by William R. Ware, PhD, 06/2012 (http://www.yourhealthbase.com/archives/issues.htm) regarding an article and book concerning aspartame and its potential liabilities, written by Woodrow Monte, PhD, Professor Emeritus of Nutrition and Food Science at Arizona State University. His thesis concerns the metabolism of aspartame into amino acids and methanol and the further metabolism of methanol to formaldehyde at certain points in the human body. Human metabolism of methanol is quite different from animal metabolism and many of the “safety” studies used by the FDA to approve aspartame were done in animals. interestingly, the FDA approved aspartame in spite of objections arising out of internal scientific reviews and from outside experts.

    • Thanks for sharing. I think this fits in the camp of an unknown risk and a great reason — based on mechanism and logic, but not clinical data — to keep aspartame intake in check (or to avoid altogether). However, I still stand by my main argument. If the choice is between a can of Coke or Diet Coke, go with the Diet Coke. You *know* how harmful the sugar is, whereas there is a chance aspartame is harmful.

  • Oxboy

    “Just don’t make it bottled water (though that’s a whole other story).”

    Doc, did you ever follow up on this? Sorry — I’m late to the game here, but could you point me to any info you’ve relayed about bottled water being bad for us?

    • Not yet. The bottle water industry is highly unregulated, so you never know what you’re getting. A quick search will give you lots of info.

  • Mark Hoheisel

    I do think a third question…that you did address for your own case by direct experiment which is very cool, is whether cerebral insulin release is enough of an issue to block fat loss.

    It’s a struggle for me as Im very much in the habit of drinking a lot of artificially sweetened soda.

    It seems plausible. After all, insulin resistance implies a pancreas that’s extra responsive. In full blown metabolic syndrome cerebrally triggered insulin might be higher. It would just have to shut down the WAT’s energy release enough that even on a ketogenic diet, the resulting marginally greater hunger and fat intake would balance.

    If you are talking about someone sipping diet soda like water all day, there would be a lot if low level insulin releases.

    It may seem like a marginal issue, except for the massive sales of diet soda and the fact that I know from experience that if one assumes it must have no effect on fat loss because it has zero calories (more “calories are calories” distortion) then consumption can get pretty extreme.

    It also seems plausible that the quantity and frequency may be the major issues here so sweeteners in food rather than drinks may have much less impact.

    If the effect is based simply on the sweet taste and not how the sweetener is digested it’s worth knowing

  • Oli

    Hi Peter,

    What is your view on alcohol sugars such as polyols? I have reformed my diet to be low carb recently, and am eating very few carbs (fruit, a little dark chocolate and very small portions of porridge, brown rice etc.). I’m eating a lot of meat, fowl, fish, vegetables, eggs, nuts, seeds etc.

    Problem is, I miss having something a bit sweet. I like to occasionally have a sweet snack. I am a young guy and am very fit (go to the gym around 5 times a week), and have a low body fat percentage. I am not changing my eating habits to lose weight, as I don’t need to lose any weight at all. I am doing it to improve my health in the long term, as before I learnt about low carb regimes, my diet cosisted almost purely of carbs (pasta, rice, cereal, bread, chips etc.). Whilst this may be manageable now, I would prefer to improve my diet now so that as I grow up i do not become very insulin resistant and get fat.

    However, as i said, i still miss sweet treats. I found a website (http://www.lowcarbmegastore.com/) that sells a lot of low carb snacks, bars, sweet etc. It seems like they use technicalities to illustrate a low carb content, and it seems like a lot of there snacks are sweetened with alcohol sugars which dont have to be counted as carbs on the label.

    What do you think of eating the occasional snack bar or sweet that is sweetened in this way. I know you shouldnt overdo it because of its laxative effect, but will snacks from these sort of websites be more beneficial than say a bar of chocolate from the newsagents. I wouldn’t be eating much of it at all, maybe just a little snack every now and again (would make my whole diet consist of low carb fad foods like this).

    What do you think?


    • I don’t think we know the “right” answer (yet). There are many issues at play — physiologic (e.g., cephalic insulin response in some, but not others) and psychological (e.g., never “losing” the taste for sweetness). It’s really quite a personal decision and one that folks should be willing to monitor within themselves. What is clear, to me at least, is that if you’re choosing between sucrose and xylitol, for example, it’s a no-brainer.

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  • Chris Hardin

    Hi Mr. Attia,

    In this article, you state:
    ” While it might be the case that you can harm a rat with aspartame, it seems you need to force the rat to eat its bodyweight in aspartame every day for a year to do so (I’m being a bit facetious, but you get the idea). ”

    However, a quick Google immediately finds studies claiming the opposite, that there was a higher frequency of cancer in rats consuming aspartame.


    How do you reconcile this? People ask me about aspartame all the time.

    • On a per weight basis, the amount of aspartame you feed a rat to harm it is significantly greater than what a human would or could eat. I’m not telling anyone it’s ok to consume aspartame, I’m just saying it’s probably a lot less harmful than sugar.

    • How much relevant to us is that rats endure high doses of aspartame without negative consequences? Not much, given that rats have an effective catalase metabolizing methanol in their livers and we do not: read the review by William R. Ware of While Science Sleeps, a Sweetener Kills. On the other hand we have no problem to metabolize low doses of fructose, where it is used to replenish liver glycogen (at least at breakfast time).

      The note of the FDA about aspartame is an unlaughable joke.

  • Anna

    I’ve read these user experiences with interest and would just like to add that I have tried aspartame, cyclamate, acesulfame-k, splenda (sucralose), xylitol and stevia. I had no reaction to any of them in terms of blood glucose or side effects, with the exception of some diarrhea with the xylitol, but this only happened the first couple of times I ingested it. I don’t use large amounts of any of these, just in baking, making ice-cream and desserts. I am keenly interested in any new studies that may reveal long-term negative effects, since I am not experiencing anything negative at the moment.

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  • Alison

    Hi Peter,
    Thank you for your article. Can you speak to the potential effects on hunger and appetite with consumption of artificial sweeteners?

    • It’s probably highly variable by individual, and it hasn’t been studied (at least to my limited knowledge) robustly enough to draw unambiguous conclusions. Clearly, in some folks, artificial sweeteners are treated just like sugar (e.g., by the brain and/or pancreas), while in others, this is not the case.

  • craig

    A must read. From the oct.22 New Yorker, “Germs Are Us” by Michael Specter.

    Among other things ,it discusses the obesity crisis in terms of certain bacterias that are no longer present in our bodies, as a result of antibiotics. antibiotics are used to fatten animals..do they fatten people?

    • Yes, very likely based on emerging evidence that altering gut flora can impact obesity. Antibiotics almost certainly play a role, but so too does the actual food we eat.

  • Carmen Said

    Just read most of the comments of all you wonderful people, and am more confused then ever I was. The reason why I was searching the web was because my husband insists that he needs to drink fizzy drinks to help him to burp. He was doing fine on just using soda water made by his soda stream machine at home. Now he has gone back to drinking Coke which has Aspartame in it and I was concerned about it as he has type 2 diabetes.
    My answer to all these suggestions is,,,,why don’t you all try to drink just plain water with a bit of lemon juice in it.
    Stay happy and healthy and God bless you all as you seek a way to stay fit.

    • Or better yet, carbonated water with lemon or lime in it…

  • PV

    A lot of research is being conducted regarding safety aspects of stevia and actually no risk has been identified. in some cases it is dose dependent. is it correct to say that stevia is also not a safe artificial sweetener???

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  • Tim

    Hi Peter

    Have you read about this research?


    The article was confusing to me. No insulin release is good. Why would they find that it is bad? More confusing info from the main stream media. I think their correlation is wrong; Obese people drink diet soda to avoid a few calories here and there. Diet soda doesn’t make them obese. Thoughts?

    • You hit the nail on the head. These are real associations, no doubt. But it’s quite likely the arrow of causation is going the other way. There certainly may be problems with diet soda (I drink at most 1 per month, and usually less), but I have a hard time imagining that ounce for ounce, diet soda is half has harmful as regular soda.

  • Roger


    Very interesting article, and I’m impressed with the depth of knowledge shown by the commenters.
    However, I do not agree that aspartame is “Safe”. Your reliance on the stamp of approval by the FDA does nothing to assuage my doubts. The FDA has an extremely poor record when it comes to the safety of drugs and products it approves. In my opinion, and I am not alone, is that the FDA is the most corrupt and incompetent agency of the US government.
    Aspartame breaks down into methanol and formaldehyde inside the human body. Does anyone here think that’s healthy? There was an incident 10-15 years ago, widely reported at the time, concerning an airline pilot who collapsed during a passenger stop. He was taken to a hospital, but the doctors couldn’t figure what was wrong until someone said he consumed several diet sodas daily, sometimes 2-4 during a flight. He had aspartame poisoning!
    Further, do you realize that diet sodas sweetened with aspartame have an expiration date? The aspartame gradually breaks down into methanol after a month or two, depending on ambient temperatures. I’ve tried an expired one, just to see how it tasted – it was disgusting!

    Thanks, Peter. I will be a regular reader from now on.

    • Roger, well I certainly agree that aspartame tastes horrible! I think the question is still one of dose. If there is toxicity at “normal doses” of aspartame, it must be small, lest we’d be seeing more of it. Great data do exist on consumption. Anecdotes aside, clearly the safest thing to do is avoid it, but if I was forced to choose between a diet coke and regular coke….I’d drink the diet coke. I’d prefer soda water with lime to either, though.

  • Marjorie

    Hi Peter! New reader to your blog, fascinating stuff. I’m curious about this way of nutrition in regards to child development and wondering if you have any thoughts/data/research on how/what to feed growing children? Any ideas on the most favorable sugar substitute for them (in terms of health not taste)? Many many thanks! 🙂

  • Jessica

    Being overweight may be unattractive in the opinion of society but it doesn’t mean the perfect picture of unhealthy. Diabetes is one of the main reasons people get scared into “healthy” eating and exercise. The reason overweight people have a higher risk of diabetes is because they eat more diet foods to let’s face it appear more attractive. Eat sugary foods with aspartame and I guarantee you will have diabetes in a short period of time. The reason people can’t see the harmful connection is that the new generation never had a chance to know what good food tastes like. Remember, greed isn’t just about money. You can be greedy for wisdom.

  • Joe

    Hi Peter!

    Thank you for this posting. I always appreciate your willingness to stay away from dogmatism and your guarded approach to interpreting the evidence.

    My question is regarding sweeteners (including Low GI sugar alcohols like xylitol and erythritol) and ketones. dietdoctor.com has a very interesting post concerning sweeteners. After consuming a Pepsi Max Dr. Eenfeldt monitored both his blood sugar and his ketones. He observed no significant movement in his blood sugar levels but did observe a very significant decrease in his blood ketone levels.

    I have also read some other studies that observed similar phenomenon with xylitol. Is is possible that sugar substitutes for some reason unrelated to insulin and blood sugar can have a depreciable effect on blood ketones? Could this also explain why many people have experienced weight loss problems they have attributed to sweeteners?

    Here is the link if you have not read his post: http://www.dietdoctor.com/is-pepsi-max-bad-for-your-weight

    • Thanks for sharing, Joe. Had no read this. The effect could be mediated by a cephalic insulin response or some other impact on hepatic glucose output, I suppose?

  • Cynthia

    Dr. Attia,

    I was wondering if there are data regarding insulin response to diet soda. I am admitting a diet dr. pepper fan.

    • Short answer, is aspartame should not raise insulin, but it might, as I explain in this post.

  • Cynthia

    That was what I gathered with the pre-prandial pancreatic response to food stimulus. I really don’t want to give it up and am hoping it doesn’t affect metabolism. Thank you for your response.

    • Probably the best thing to do, Cynthia, is a self-experiment. If you’re stalled in some way, see what happens if you sub sparkling water for Diet Dr. P for 4-8 weeks.

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  • Kyth

    About 10 years ago I used to be very addicted to Diet Coke– drinking 4-5 32oz buckets/day. I just wanted it all the time. Eventually I started having issues where I was throwing up very often (with no other side-effects), with some random acute pain like an ulcer. A doctor told me he thought it was the aspartame and that I should quit diet sodas immediately. I did. No more stomach issues, ever again. Could be a coincidence, or some other cause, but I’ve been hesitant since to consume anything with aspartame. I’ve tried Splenda in things, but it has a sickly-sweet-chemical taste that I just can’t get past. I have had really good luck with the xylitol, though. But now that I’ve been in ketosis for about a month, I rarely crave things that would require it.

  • Suzie

    Hi Peter
    I’ve only just discovered your blog and could spend hours here! It’s wonderful informative and well researched.

    I thought you may be interest in a program that aired in Australia last Thursday on ABC’s Catalyst program on Saturated Fat and Cholesterol and how we’ve all been fed a lie for decades!
    Part II will be airing this Thursday night. I have no associated with the ABC or this program but as one interested in optimal health and nutrition, thought you might find it of value.

    In Good Health!

  • Avery

    Peter, your response to “Wally” on 22 Apr 2012 seems to imply that you do not believe that sucralose induced gut dysbiosis is relevant to fat accumulation. However, on 27 Nov 2012 you state that there is emerging evidence to support the concept of gut flora being relevant to obesity. Have I misunderstood your initial take or was there a change of heart over those months?

    Personally, I feel better without any artificially created sweeteners in general, and lots of water. But I must be one of the cephalicly challeged individuals with regard to insulin response because when I’m in ketosis, any sweeteners at all, even the natural ones, leave me foggy for 30 to 60 minutes or so.

    I guess my question is, is your general stance that we should choose the lesser of the evils presented? As with the grass fed vs grain fed beef debate? Also, do you feel that, realistically, the potential dysbiosis from sucralose is enough to negate the impacts of an improved and sugar/carbohydrate restricted diet?

    I’m inclined to believe that with a high quality pro/prebiotic, and healthy choices in the rest of the diet, the impact of sucralose would be minimal, and most people would see positive gut flora changes anyway. Maybe I’m just making random statements. And anyway, the study I have only documents the dysbiosis in male rats.

    • The latter. I think my understanding of nutrition continues to evolve daily.

  • Dave

    During the blog a comment was made that there have been no accounts of toxicity from aspartame and other artificial sweeteners. This is not an accurate comment. There have been tens of thousands of reported accounts of toxicity. The chemical reaction occurring from digestion produces formaldahyde and has been advertised in dozens of articles and is medically accepted. During 1995 the FDA stops taking accounts of adverse reactions to aspartin after 75% of there total complaints were related to cases of aspartame toxicity. The FDA has recieved dockets for the removal of aspartame as a neurotoxic drug.

    However I don’t believe chemical sweeteners and natural sweeteners like stevia are in the same boat.

  • Manish Kataria

    I knew that sugar & Aspartame have their side effects. But didn’t knew that Stevia is also harmful.
    In this notion I thought that Coca Cola which uses stevia is also better that HFCS. But also my doubts got cleared after I read this article. http://5best.in/shocking-facts-about-coca-cola/

  • Carole Saylor

    You can say what you want to say about aspartame being harmless but from my personal experience, I have to strongly disagree with you. I have experienced migraines that are solely related to my consuming food containing aspartame. I even did an experiment with myself because I didn’t want to believe it. I found I could consume one can of diet Coke per week with no ill effects. However, if I consume two cans, either the same day or within a day or two of each other, the following morning I will wake up with a headache which will hang on most of the day. If I have another can of Diet Coke, the next morning the headache will be much worse and will last the entire day. If I haven’t learned my lesson by this point the headaches become debilitating and I can’t function because of the severe headache pain. To make matters worse, no headache medicine or pain killers will take the headache away. Only staying away from aspartame for a prolonged period of time, (a week or more) will cause the headaches to go away. I don’t have this problem with Splenda, saccharin, or sugar alcohols as I use them in cooking and my coffee every day.

  • Marianne

    You really really need to inform yourself on aspartame if you are going to write these kind of articles! Telling people there’s not research to prove it is harmless in humans………really? Do you have you head in the sand? Bad, bad, bad advice and information!!!!!!!

    • Thanks for clarifying that. Let me get my head out of the sand and get back to you.

  • Manicam

    Thank you for a very balanced and refreshingly sane blog.

    As you have clearly stated, we will continue to gain more knowledge over time. And the wily use of statistics to confuse people into extrapolating from correlation to causality very often works. I have friends of “The Alkaline Water School of Philosophy” who scream that aspartame is poison! I lapse into temporary deafness.

    I have to guiltily admit that I do fly in commercial airplanes and I do use aspartame for my coffee and tea – since I was in my twenties. But I haven’t graduated to sky diving as I am only 69. Save that for when I am 80 and need more excitement.

  • Joe

    Hi Peter.

    Thanks for this thoughtful and balanced article. I’m sorry for the flak you take for these things. Some people just can’t seem to understand that just because they have had a negative personal experience with Aspartame, that doesn’t mean it’s harmful to the general population. On to my question.

    Regarding the cephalic insulin response: How in the world can people think that it could be comparable to drinking a full sugar Coke? Maybe I’m wrong here, but wouldn’t the insulin response from drinking a Coke be fairly substantial? If I downed a 20 oz Diet Coke and I experienced a comparable insulin response to that of a regular Coke without the corresponding rise in blood sugar, wouldn’t I go into shock? My blood sugar would plummet to dangerous levels I would think.

    • I don’t know and while I can’t stand diet soda and such, I really think they are a better alternative to the “real” thing.

    • Vicente

      Hi Joe,
      dairy products like milk or kefir do have an insulinotropic effect: our body produces more insulin than expected for their carb count. So you have the insulin but not the carbs and I don’t know why but people don’t go into shock after drinking a couple of glasses of milk.

  • Inkosikathi LaWilliams

    Dr A
    Great blog. Do you or anyone know if we can purchase fresh miracle fruit. I have failed miserably at growing the tree in California. It is a tree indigenous to West Africa and the berry like fruit changes the chemical make up of your tongue taste buds, thus everything you east for an hour after taste sweet. Lemons like lemonade etc.,

    I had the pleasure of eating them while in a west Africa, but I have also eaten them from a tree a doctor grew in South Florida. The exact name of the tree is Synsepalum Dulcificum, but if you google Miracle fruit tree it comes up. I want to use these to avoid sugar and sufar substitutes.

    Again thanks for your great info


  • Robin McFee

    Would you categorize cravings for starchy foods the same as for sugary foods?

    I found cravings for sweet foods completely dissipated within a couple of weeks of dropping both real and artificial sweeteners but I do occasionally get an almost irresistible craving for popcorn. I wonder if there’s an underlying reason or if it’s just the result of past eating habits.

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  • Sheila

    Peter – I know you and some others have recommended (or used) BioSteel HIgh Performance Sports Drink (as a BCAA drink). I want to have a daily dose of BCAA along with KetoForce. But, the BioSteel product has Sucralose in it! Is there one that does not have it? So, this would not be the occasional diet drink – it would be daily. Is it a good trade off? I am insulin resistant at this point. I was told BCAA’s are important and that they are a good buffer to KetoForce (Dr. D’Agostino) and I know you have used KetoForce also.

    Also, I did try the powdered BCAA that won’t dissolve in water and I just can’t get it down!

    Thanks for your consideration of my question(s).


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  • PK

    It seems that every time I catch the news, there’s a new study that implicates artificial sweeteners in weight gain. Many of them are shockingly inept, often having little regard for cause and effect–they can’t say, for example, if people are overweight because they drink diet soda or drink diet soda because they are overweight.

    What concerns me is the supposition that consuming ANY amount of artificial sweetener is enough to make one’s metabolism go crazy. It strikes me that there’s more at work here than simple scientific investigation, as if though the studies are being geared to show that anybody who attempts to “cheat” their bodies by consuming an artificial sweetener deserves to gain weight. It seems to follow from the same mindset that all genetically modified foods are unhealthy.

    I have followed steps found on this web site and have lost about 15 lbs. over three months. Prior to this, I took myself down to roughly 1400 calories a day, of which 400 came from sugared coffee–and continued to gain weight.

    I lost the weight simply by avoiding ALL sugar six days a week and enjoying a small amount on the seventh. I haven’t even addressed carbs and eat anything else I want. And yes, diet sodas are part of my daily intake.

    Once my weight stabilizes, I’ll decide on the next step in permanent dietary change.

    Thanks for this web site and blog. It’s made a significant difference in my life.

    • Below is response I posted today to a question about this study on a more recent post. I agree with your skepticism on this. This is such a sloppy field.

      Here’s my response on the particular study that just came out:
      The mouse data are useless. Who cares what happens in a mouse. Not the species of interest. The experiment that needs to be done is as follows:

      2 groups eat the exact same food for 2 months Group 1: drinks 3 soda waters per day; Group 2: drinks 3 diet sodas per day

      Both groups consume the same # of calories, type of calories, etc. and even same amount of fluid and carbonation.
      Measure glucose disposal and other tests of insulin resistance pre- and post.

      Easy study…hope it gets done. Until it does, I’m not convinced that diet soda is harmful, but it’s a very interesting question and it needs resolution.

  • Ted Everson

    Peter or anyone else, what are your thoughts on the recent Nature publication concluding that artificial sweeteners can induce glucose intolerance (in mice)?


    • Pete Bernardin

      In respone to Ted Everson’s question on the Nature Article: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature13793.html

      “Artificial sweeteners induce glucose intolerance by altering the gut microbiota”

      I do not know the best way to measure glucose intolerance in mice. The authors do this by noting differences in the short-term Blood Glucose Levels (BGL) during Oral Glucose Tolerance (OGT) tests of mice that were fed large amounts of artificial sweeteners (the sweetener was primarily saccharin) over several weeks. Whether or not this has any clinical significance in humans remains to be seen. Their paper certainly does not prove this.

      The mechanism behind this could be explained by the gut bacteria of sucrose fed mice consuming a larger proportion of the glucose during the OGT as compared to that of saccharin-fed mice. Would this be bad for humans? Who knows?

      As far as any conclusions from this study about the effects in humans, they are minimal at best. The study has the “self-reporting” issues that Peter has talked about here already:
      Here is an excerpt from their methods:

      “Long-term NAS consumption was quantified directly from answers to an
      explicit question regarding artificial sweeteners that participants filled out in their
      food frequency questionnaire. “

      They surveyed more than 400 people, and found that long-term users of Noncaloric Artificial Sweeteners (NAS) were more likely to have higher fasting blood sugar levels and were more likely to have signs of impaired glucose processing, compared with people who don’t normally use NAS.

      –BUT IS THIS CAUSE OR EFFECT? The authors propose this as CAUSE, I think it is more likely EFECT.

      General Comments: This paper focuses on the glycemic risks of drinking various liquids. Yet the glycemic response is only one measure of the health risk of a drink. There are also lipogenic risks such as those of fructose sweetened beverages which have a very low glycemic index. The majority of the work in this paper focuses on the glycemic effect of saccharin in mice. Conclusions about the risks of NAS versus sucrose are incomplete without also addressing the lipogenic risks of NAS, if any. I doubt there are.

      In my opinion, the authors do not have enough data to support their hypotheses of the risk of NAS in humans.

      • Very well said, Pete. I hope someone gets around to funding the relatively easy experiment that could resolve this question.

    • Don Peven

      I find it very hard to postulate a mechanism through which artificial sweeteners could alter gut microbiotia which would then cause glucose intolerance (at least in humans). Consider that the small intestine, where food is absorbed, is sterile. It isn’t until you get all the way into the colon that there are any bacteria present, and the colon is mainly there to reabsorb water from your intestinal contents; no digestion takes place there. The only way I can think of that alterations in colonic bacteria would influence carbohydrate metabolism would be:

      1) the altered bacterial flora might produce some toxin or byproduct that would alter glucose tolerance; or

      2) the altered bacterial flora might digest some formerly indigestible material that makes its way into the colon, turning it into sugars that might be absorbed.

      Both possibilities seem pretty farfetched. My bet is that the findings are spurious.

  • Joe

    I always love your insight Peter. Thanks for the article. What type of device do I need to purchase to test my insulin levels (not blood glucose)? I am very curious about the use of sugar-substitutes because even otherwise very competent people make wildly different claims about them but I can never find anything solid. First off, why in the world is it so hard to find any information about the insulin response from sugar substitutes? Just stick two groups of people in a room, give them a glass of water mixed with the selected sweetener and test them. SUPER easy. Anyway, I am tired of trying to find reliable information so I am going to test myself, costs be damned. Help please?

  • Ryan

    Dr. Attia,

    I’d be curious to hear your opinion on the science behind this video entitled, “Aspartame: The Bitter Truth
    Behind this Toxic Sweetener” that has been receiving quite a bit of attention: https://www.youtube.com/watch?v=TB6L9S_jc5E

    The video asserts several things: First, that the high amounts of phenylalanine found in aspartame can deplete your serotonin thereby leading to depression. And secondly, that the very weak phenylalanine-methyl bond allows the methyl group to break off to form methanol which is in turn converted to formaldehyde by alcohol dehydrogenase. The lack of an enzyme in the body to breakdown formaldehyde leads to a build up of formaldehyde in cells that can eventually lead to cancer. Unlike humans, other animals are able to break down methanol into harmless formic acid which makes toxicology testing on animals a flawed model.

    Thanks so much for the blog!

    • Ryan

      Apologies – just noticed you have addressed this elsewhere in the comments.

  • JLH

    Hi Dr. Attia,
    Thank you for all the information on low carb endurance training.
    I am a 29 yo F, and have been low- ultralow carb, high fat, moderate protein for nearly a year now, while doing ultramarathon training. Everything is great EXCEPT THE RECURRENT SKIN RASHES APPEARING AFTER DROPPING 2 POUNDS AND BEING IN KETOGENESIS FOR SEVERAL CONSECUTIVE DAYS

    I was hoping you may know something about the “keto-rash” that I have read on a number of low carb dieter threads. I’ve been eating cheese and nuts all my life with no issues prior to this carb slashing diet. I am suspicious it may be related to ketogenesis.

    Thank you in advance for any insight you can provide and I will update if anything changes after increasing carbs to 100 g/d
    Sincerely, Dr. JLH

    FYI details on rashes:
    I have an erythematous, raised, itchy, non-painful rash with poorly defined borders on the volar surface of one forearm (4 inch diameter)(in the elbow- crease), a hyperkeratotic, scaly, erythematous, non-itchy, non-painful rash along the peripheral border of the my lips (where the skin of the face meets them) and a well circumscribed slightly hyperkeratotic/scaly, erythematous, well circumscribed lesion on my anterolateral neck, a few inches above the collar bone (2 inch diameter) . The rash on my forearm looks like candida to me, but has not responded to topical antifungals and as an athlete who has never had any fungal infections (I think because I eat lots of raw garlic and onions), I think it’s pretty unusual to have fungus on the neck and forearm but not have any involvement of the groin, axilla, feet/toes.

    • Very intersting, and yes I have heard this from a few folks. I would check with Steve Phinney. If anyone knows it will be him. I’m just too overwhelmed these days to do the digging. But do report back!

    • Sean Brazelton


  • Mike

    I can say with confidence that aspartame caused and triggers my seizures and destroyed my life. It is by far the worst chemical in foods and should be replaced w a different sugar substitute (the rest seem a lil more safe).

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  • Gerry

    I’m just wondering if you have any opinion on the research showing an adverse link between artificial sweeteners (including Stevia) and their affect on intestinal microbial, (good bacteria vs. bad bacteria). The idea that these sweeteners, although they do not increase blood sugars levels, may be linked the development of diabetes and metabolic syndrome by replacing the so called good bacteria in our gut with with a proliferation of bade bacteria that interferes with proper digestion. Such as the article outlined in here… http://www.the-scientist.com/?articles.view/articleNo/41033/title/Sugar-Substitutes–Gut-Bacteria–and-Glucose-Intolerance/ .

    Thanks for all your work and free advice. I am a recovering T2D well on my way to a healthier life in my old age.. lol

    • Gerry

      Oops… Sorry I just found another post on this subject I missed before..

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  • John Garesche

    Dr. Attia,

    I am surprised that you seem to brush off the importance of gut biome in obesity – or at least you allow Pete Bernardin to do that for you. Suggesting that the biome in mice is not equivalent to the biome in people is not supported in the literature. Are there differences – of course! But when there is limited data – you go with the data, not with the lack of data. The study provided attempts to indicate that there are similarities – in that the NAS (Noncaloric Artificial Sweeteners) influenced human gut biome was introduced into mice and similar results were found. Testing humans is always far more complicated – and understanding gut biome is even more complex.

    Overall, it is an area of study with limited research, but more and more data is being produced supporting the importance of gut biome in health and weight management:
    (I could go on – there is a lot out there).

    What is clear is that we really do not understand the gut biome. The studies out there on sugar versus NAS do indicate you will gain more weight with sugar, but they don’t compare it to water. This is a pretty good initial study. There is a lot more needed – and I would hope you would encourage that rather than brush it off.

    In the end, I also wish you would emphasize your final conclusion – which is highly valuable: The best thing is healthy water and limited sugar and artificial sweeteners.

  • Matt Hopkins

    Hi Peter,
    Here in the UK doctors have been looking at how sweetener can mess up the gut bacteria which may account for a rise in insulin levels even when using the artificial sweeteners. They used a new highly sensitive monitor in a study on people
    You might be able to get the TV programme on YouTube

  • rick

    Id like to run this thought past you. Please shoot it down or comment as you please. If you drink a soft drink that contains an artificial sweetener, your brain registers the sweetness and anticipates that caloric intake is on its way. When the calories do not arrive the brain doesn’t know it has been duped. The psychology of the situation would then lead that person to seek real sweet alternatives that deliver calories. What Im saying is that are you, as a consequence of eating/drinking something artificially sweet increasing the risk of then (over) eating something else to compensate for the initial sweet “hit” that wasn’t associated with any caloric value? Have any studies been done on this?

    • Yes, this has been studied. Results seem mixed and heterogeneous, but it’s one more reason to avoid artificial sweeteners if you can.

  • Tanya

    I’m curious what percentage (a rough guess ?) of people , when you tell them to eliminate the sugar substitutes because they can’t lose weight despite doing everything else right, do actually notice a difference?

  • Callan

    Actually, you should reconsider adding dextrose to your list of dangerous sugars. Dextrose is simply another name for glucose. It is in fact d-glucose. There is nothing harmful about glucose. All complex carbohydrates break down into glucose molecules. Maltose is a perfectly safe glucose-glucose disaccharide that can be found in such perfectly safe products as brown rice syrup.

    If you rewatch or listen to Dr. Lustig’s lectures, you will find that there is really no concern with dextrose for the average person as even someone ingesting unhealthy amounts of it will only end up with large amounts of glycogen in their liver, which can easily be metabolised. The danger is in the fructose. Fructose is treated like a toxin in the liver and produces numerous dangerous byproducts. Thus, sucrose, HFCS, agave nectar, honey and other fructose-containing substances are the dangerous substances. However, dextrose is not. This also applied to many beers, which are made with dextrose as the yeast-feeding agents.

    All of this naturally does not extend to diabetics. Since glucose levels are what diabetics are concerned with, it is more dangerous for them to consume. However, since Lustig paints a fairly clear picture that connects fructose with diabetes, it is important that we avoid fructose-containing products more than glucose ones.

  • Leah

    I was a Diet Coke-aholic in my twenties. I started having piercing headaches (think spear through the eye) and then lost the vision in my right eye in one afternoon. The ophthalmologist and neurologist that I went to initially thought that I had a brain tumor or MS and I had scans and lumbar punctures with no definite diagnosis. I had several more rounds of vision loss in both eyes, dragged my leg for a week, had a type of Bell’s Palsy, experienced extreme weakness and fatigue and then finally developed crushing nerve pain in my spine. These symptoms followed the relapsing/ remitting pattern and lasted for about 7 years. Things got so bad that I was afraid that I would have to apply for disability. A friend saw an article about the dangers of Aspartame and said “This is you”. It definitely was me. I stopped drinking the Diet Coke and avoided any other products with Aspartame. Despite a diagnosis of “MS” at Vanderbilt, I made a miraculous recovery. I will never touch the stuff again. I’ve known at least 3 other individuals who have had the same problems with Aspartame.

  • George

    33 years ago when I retired from the military, I was informed that my blood sugar level was high. To say I loved everything sweet would be an understatement! I started switching to diet sodas and artificial sweeteners in my coffee.
    Shortly after I started suffering from TIA. I didn’t make a connection at the time to my use of artificial sweeteners. T he TIA’s became more and more frequent, occurring about 3 to 4 times yearly. I was also eating lots of artificially sweetened candies. I recently suffered some sort of seizure but think this may have been brought on by dehydration. About 5 months back I stopped drinking diet sodas, eating ‘sugarless’ candy and went back to using real sugar in my coffee. I have not since had any problems with TIA or seizures. I’m hopeful these problems will not return. Time will tell.

  • I used to be an avid soda drinker – like all the time. Probably 6-7 glasses of pepsi per day. Then everything started coming out about how bad it was for you with all the sugar so my family switched over to diet soda. I probably drank diet soda for a good 5-6 years, again, 6-7 glasses per day (strangely enough, I now think diet soda tastes wayyy better than the regular stuff).

    When I was later into college I started taking my health a bit more seriously and the diet soda was the first thing to go. Holy cow! I couldn’t believe how much better I felt not cramming that stuff into my body at all times of the day. I felt more awake, more hydrate and had way more energy. I’m super happy I switched.

    Another thing that I was horrible with was chewing gum. Same thing, started with sugar, then went to non-sugar. Then I found out about aspartame and how it could potentially be bad for you, all that stuff. I obviously didn’t find anything that proved it was 100% bad, but it didn’t make sense to constantly consume a chemical that I didn’t know a whole lot about, so I replaced it with xylitol gum. Again, a world of difference.

    I hate getting on my high horse about being natural and such, but I’ve personally noticed a huge difference in my life since I started focusing on consuming more natural products. And there are tons of great benefits (the best of which is I don’t have nearly as many weight issues!).

    • Peter

      I used to take 5 to 10 Assugrin in my coffee, 6 to 8 times a day. One beautiful morning I could not find my car which I park every evening around the block on a free parking space. This continued every day now. Even when memorizing my parking spot in the evening I did not know it the next morning.
      Luckily a customer lead me to some studies about artificial sweeteners and Bingo! I found the reason. Immediately I stopped taking artificial sugar. Already the next day I was back to normal.
      This is not the only product we put into our body. This is not the only platform about the effect food has on our health. These here are all intelligent people concerned about their and their families health and well being.
      When are we occupying the streets in millions to demand our right for natural food and stop the toxic invasion coming from global corporations that take away our capability to live a beautiful life? Do we wait for our children to do it? Please don’t, y then they will be death and forgotten for ever.

  • Samantha Baker

    Peter – Any updates on how your body is responding to that high quality allulose you were sent? How does the CGM data look? Thanks!

  • Samantha Baker

    Great news. Now when can the rest of us get some allulose?

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