February 15, 2012

Nutritional biochemistry

How can carbohydrate restriction be healthy if it means limiting “natural foods” like fruits and vegetables?

Read Time 9 minutes

This week I’d like to tackle one of the most important questions that I get asked.  However, before getting to the question, I think it’s worth investing a few minutes to frame this discussion around a theme tightly linked to it — sugar.

If you’ve been following the nutrition news lately, you may have noticed that Dr. Rob Lustig has made some headlines.  If you’ll recall, Dr. Lustig is arguably the world’s expert on fructose (i.e., fruit sugar) metabolism, and I included a link to his now-gone-viral YouTube video on fructose toxicity from 2+ years ago in my post, Sugar 101.  In the February 2nd issue of the journal Nature, Dr. Lustig and his two colleagues make the following case:

  1. Sugar consumption is linked to the dramatic rise in obesity, diabetes, cancer, heart disease, and Alzheimer’s disease (i.e., the diseases that cluster around metabolic syndrome).  Effectively, sugar speeds up our aging process.
  2. The metabolic effect of sugar, and fructose in particular (fructose makes up half of sugar – sucrose is 50% glucose, 50% fructose; HFCS is 45% glucose, 55% fructose), is nearly identical to that of ethanol (drinking alcohol).
  3. As such, sugar should be regulated in a manner commensurate with the damage it causes.

Let me lay out a few facts.  First, our consumption of sugar is increasing at a staggering rate.  We consume, on average, about four times the amount of sugar today that we did 40 years ago, even though our consumption of sucrose (the white crystals) is going down.  How, you ask?  Because we have more than made up for it with the ubiquitous addition of high fructose corn syrup (HFCS) to darn near everything we eat (e.g., cereal, pasta sauce, salad dressing, virtually every form of “low-fat” food out there, condiments).   Remember the “Peter Principle” – when you see “low fat,” run the other way, as it is almost synonymous with “high sugar.”

The figure, below, from the Nature paper shows the amount of sugar (excluding fruit) that each country produces, in per capita figures.  If you factor in fruit, obviously the numbers are much greater.  A quick glance at this figure shows that (excluding fruit), the U.S. is the reigning undisputed champion of sugar production at over 600 calories per person per day, which means over 175 gm of sugar per person per day, (excluding fruit and fruit juice).   To fully understand why we produce so much sugar requires a discussion beyond the scope of what I want to write about today, but I’m sure most of you already have a pretty good idea: economic incentives.

There’s another interesting observation that can’t help but poke you in the eye when looking at this figure.  How many times do you ask (or get asked), “Why do some cultures eat carbs like rice and not get the same diseases we do?”  A quick glance at China, for example, sheds some light on this.  They may eat rice, but they sure aren’t producing (or eating) much sugar, on average.  Furthermore, the distribution of sugar consumption within the country is wide.  In other words, while the few wealthy people do eat amounts of sugar approaching Western amounts (along with other simple refined grains), the vast majority of non-wealthy inhabitants do not.  So while some have asserted that animal products and fats are the clear culprits explaining the different disease patterns in Asia, they’re missing this important point:  Given the absence of mechanistic and evolutionary reasons why animal products and fats are bad for us, is it more likely that sugar consumption is the single biggest factor differentiating the state of disease across these populations?


Global sugar glut Nature Lustig paper figure
Image credit: Lustig et al., 2012 in Nature

So what’s the upshot of this graph?  Well, for starters we eat a lot of this sugar.  Second, we export it, too.  This wouldn’t be a problem, I guess, if sugar were not so harmful.   How harmful is sugar?  For a long reminder, read Sugar 101.  For a very quick (by proxy) explanation take a look at the following table, also from the Nature paper, and previously presented by Lustig.


Table 1_Lustig Nature paper
Image credit: Lustig et al., 2012 in Nature

This table shows, side-by-side, the health problems that occur with chronic ingestion of ethanol (i.e., drinking alcohol) and fructose.  [Remember: fructose is the sugar found in fruit and fruit juice, but it also makes up 50% of table sugar (i.e., sucrose) and 55% of HFCS.]

I think the figure speaks for itself and suggests that about two-thirds of the pathology that afflicts a heavy consumer of ethanol also afflicts a heavy consumer of fructose.   As Lustig points out, this should not be terribly surprising, given that we ferment ethanol from fructose.

Let’s summarize:

  1. We produce and eat more sugar than any other country on earth, and do so more than at any other time in history.
  2. Consuming sugar is not just “bad” because of the “empty calorie” hypothesis (i.e., the reason one should limit sugar is because the calories from sugar are not as valuable as those from, say, protein); it’s bad because sugar is a chronic toxin.

One last point before we jump in:  Before you angrily email me, or say awful things about me for daring to suggest that Michelle Obama and the USDA might be wrong in recommending we eat 5-6 servings of fruits and vegetables (many vegetables are full of fructose, too) per day, keep one thing in mind.  I am simply making a few points and you need to decide how you want to interpret them and make personal choices around them.  We are all genetically different, and therefore have a very different genetic predisposition in our sensitivities around these foods (and all foods in general).

There are some folks out there who can eat enormous amounts of sugar and experience very little ill effect.  My wife is the poster child for this phenotype – though she doesn’t any longer, she could eat unlimited amounts of sugar and not gain weight*.  Furthermore, as we age, we generally get less adept at processing sugar, and therefore with each passing year a “fixed dose” of sugar appears to cause greater and greater harm to an individual.

*Note that I only commented on the “weight” portion of her phenotype.  When my wife did reduce her sugar intake, she experienced many benefits in her health, perhaps most importantly, her improved cardiac disease risk profile measured by advanced lipid testing.

Here are the points with which I want to challenge you:

  1. Before you assert something is “natural,” be sure to understand what you mean by “natural.”
  2. Don’t be afraid to question the notion that all things “natural” must be healthy (and by extension, that all things “un-natural” are unhealthy).

Let’s address these points in order.

Point I: How do you define “natural?”

Most people assume the fruits and vegetables we eat are “natural,” but in reality fruits and vegetables of today bear little, if any, resemblance to their original form.  Let’s take corn as an example.  [I’m choosing corn because (i) it’s illustrative of the broad science and progression of agriculture, and (ii) I happen to read a lot about it, as I find the evolution of corn cultivation fascinating.]   Bear with me for a moment, as I tell this story.

7,000 years ago — a sliver of time on the evolutionary scale — corn as we know it today was a plant called teosinte.  Teosinte was about the size of your thumb and had a few (maybe 4 or 5) kernels.  Over the next few thousand years we began the shockingly quick (by evolutionary standards) process of “domesticating” this crop from its “natural” state into subsequent states of what we now refer to as maize.   By domestication I mean the process of successive selection of crops that had the most advantageous features for our needs.  Sort of like “domesticating” animals so they would cuddle up with us on the couch instead of trying to eat us.

How did the process of domestication work?  As an example, farmers selected teosinte crops which were larger, had more kernels, were more resistant to drought, and were more resistant to pests and predators.  This process went on, growing season after growing season, until about the period of time leading up to World War II and morphed teosinte into a very different looking crop.  Hence, the progeny crop, maize, looked very different from the parent crop, teosinte.   At that time, around WWII, the average farmer in the U.S. could grow about 18 bushels of corn per acre per year, though progress in yield increase had been stagnant for a few hundred years.

Around 1940, however, the productivity (i.e., the yield improvement) and morphology (i.e., the physical “look”) of corn growth began to change dramatically for two main reasons.  First, this change was driven by the introduction of technologies to make cultivation more efficient (e.g., crop rotation, use of fertilizer and pesticides, improved irrigation).  This was referred to as the “industrialization” of agriculture.  Roughly in parallel to this effort, advanced biologic techniques of active breeding (genetically crossing one plant with another so they could mix genes – the same things animals do when they mate) and mutagenesis (disrupting the genes of the crop, typically using chemicals or other agents, like radiation, to change the genes of crops) significantly increased the functional genetic diversity of the crops, year after year, further increasing yields and other desirable crop properties, such as cost of production.

Furthermore, in the last 20 years or so, the introduction of genetic modification (GM) has made maize even more robust and genetically fit.  Today U.S. farmers can grow nearly 200 bushels of corn per acre per year, up from less than 20 bushels per acres per year in 1940.   Below is a figure showing corn yield data from the National Agricultural Statistics Service, which shows the almost unrelenting productivity gains in corn cultivation over the past 70 years.  The world’s leading technology companies leading this charge (Monsanto, Pioneer, Syngenta) are projecting yields of 300 bushels per acre per year by 2030.  In other words, with each passing year, technology is making corn more and more robust, and therefore more and more distant from what is “natural.”


US corn yields for past 50 years

What about apples? Oranges? Strawberries? Peas? Carrots? It turns out the story I’ve told for corn is virtually identical for every “crop” we grow today, including all of our fruits, vegetables, and grains.  I know what some of you are thinking, “I only eat organic non-GM fruits and vegetables, so I’m ok, right?”  Unfortunately not.  Genetically modified (GM) plants and crops are different from non-GM plants and crops in small genetic ways that generally make them more resistant to pests.  But the hallmark differences between, say, teosinte and modern maize are 95% accounted for without the addition of genetic manipulations.  For the purpose of this discussion, genetically modified crops are a moot point.  In other words, what we grow and eat today, even if we buy “organic” or “non-GM” has absolutely no resemblance to what was “natural,” say, 10,000 years ago.

So the next time you bite into a Fuji apple half the size of your head (these used to be my absolute favorite things to eat, by the way, and I’d easily consume 3 or 4 per day), ask yourself what it has in common with the “apples” your ancestors ate.  The answer, not surprisingly, is very little.


Natural foods

Point 2: Who says everything “natural” is good for you?

The next point I’d like to address is dispelling the myth that all “natural” substances (notwithstanding the argument, above) are healthy.  Let’s examine the role of toxicity in natural things we ingest by first distinguishing between two types of toxicity: acute toxicity and chronic toxicity.  Simply speaking, acute toxins are toxins that can kill you quickly, if you are exposed to a single dose, or a series of repeated doses in a short period of time. Conversely, chronic toxins are toxins that don’t kill you from a single exposure, but over time multiple exposures can kill you.

While there is no shortage of “man-made” toxins in the world, you might be surprised to learn how many “natural” toxins exist, too.  Let’s examine a naturally occurring acute toxin, a naturally occurring chronic toxin, and a naturally occurring toxin that is both acute and chronic.   The figure (below) shows each.

  1. Perhaps the most singularly potent acute toxin on earth is a molecule called tetrodotoxin, or TTX.  Tetrodotoxin is a nerve toxin that blocks sodium channels in our cells.  TTX is so potent that less than 200 pounds of this compound would kill every person living in the United States. In other words, it’s about 10 times more potent that cyanide.  Here’s the catch: TTX is found in nature – it’s 100% natural.  It’s found in puffer fish, newts, toads, and several other sources.  Several people die each year from exposure to TTX when they unknowingly consume animals containing the toxin.
  2. Tobacco is also a naturally occurring substance.  Whether smoked or chewed, however, it has many forms of chronic toxicity, primarily related to its carcinogenic (i.e., cancer-causing) properties.  In other words, you won’t die from smoking one cigarette or chewing one pack of dip, but if you do it enough, you might.
  3. Finally, ethanol is both an acute and chronic toxic.  While acute toxicity is rare, it is possible to overdose on ethanol (toxicity in this case is usually related to respiratory depression – that is, you stop breathing).  More common, of course, is the chronic toxicity of ethanol, which is well understood and well-documented.  For a quick reminder, take a look at the table I showed earlier in this post from the Nature paper.


Natural toxins

So there you have it.  There are plenty of “natural” compounds on earth that are harmful.  I am not suggesting that eating a Fuji apple is as toxic as smoking a pack of cigarettes, but I am saying that once you begin to understand the metabolic pathways of fructose (there are about 25 grams of fructose in a large apple) you’ll see that an apple, just because it grows on a tree, is not actually “good for you,” even though it is supposedly “natural.”  For some people, eating 10 apples a day causes no harm.  For others, eating 1 apple a day causes harm.  The goal should be to figure out what your “toxic” dose is — and stay well below it.

If you’re reading this and wondering how much sugar you can eat, it’s a bit like asking how much can you drink or smoke.  It depends.   How genetically susceptible are you to the effects of these toxins?  What are you optimizing for — short-term pleasure or long-term health?  This is where we get into the idea of dose-response.  I will address this in a future post, but not right now, as it really deserves a post of its own.


Photo by julian mora on Unsplash

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  1. Hi Peter,

    Just curious to know what your thoughts are on dark leafy greens as a whole? To me they seem to be in a whole different nutritional category than say a potato. Every morning I usually have a smoothie with half a pound frozen spinach, handful of almonds, a cup of blueberries and water.

    Also I just found this blog today and I’m really enjoying it!! Thanks for putting this kind of information out there, especially with all the hype and pseudoscience regarding diet and nutrition.

    • Mike, absolutely! Lettuce is pretty benign, BUT this does not meet you need to eat it. I eat it – not because I think it’s necessary or even “good for me.” I eat it because it’s a great way to get more fat (via high fat salad dressings), which I believe IS good for me.

  2. Hi Peter,

    Awesome blog you have here!

    As a fat person, I tried all kinds of dieting and exercising through my entire life. By reading Taubes’ books and your blog, the “low carb” hypothesis is the one that appears to be the most acceptable to me, with the most sound theory.

    But, another hypothesis that I find very acceptable is the “it’s impossible to get thinner”, because I can’t get thinner after months of low-carb eating, nor do I know anyone that has lost, let’s say, more than 20kg during or after adulthood and managed to stay thinner for more than one year.

    What do you think of this hypothesis? That some people simply can’t get thinner? Or that _most_ people simply can’t get thinner after adulthood?

    Keep up the good work! (and sorry for my english…)

    • Lucas, you’re asking a very tough question. I do believe there are so me people for whom getting thinner is very difficult, despite all measures. I’m not sure why, though. Also, it’s not clear if this results from dietary habits at an earlier time. For example, I have seen folks that have cycled weight up and down repeatedly struggle to lose weight later in life. But why? Lots of theories out there, but none proven in my mind.

      By here’s the more important point: what if you are one of the folks for whom weight loss is going to be tough. That does NOT mean you can’t improve other aspects of your health (reduce risk of disease, improve energy levels, be mentally sharper).

      • Oh, of course! 😉 I think my health has already improved a lot by not eating so much carbohydrate.

        But I really think that, in terms of getting thinner, we know very little. The science is hard to do, the data is hard to get and to interpret, and everybody (at least thin people 🙂 has the certainty that they already know how to do it.

        Just my 2 cents…

  3. I have been eating more vegetables, but not eating corn, potatoes, beets, carrots etc. I aim for foods in the low G.I. range, like green beans. I actually eat more vegetables than before. I have stopped eating fruit, even berries.. I have been worried that this is unhealthy, since eating fruit is always said to be healthy. Now I am a little less worried. I tend to think of fruit as dessert. I might have some when I hit goal weight, but it seems counterproductive to eat dessert when I am trying to lose.Everyone keeps talking about cravings for bread, pasta, and fruit, but I don’t have those. It makes me feel weird. Maybe its because I stay over 60% fat, but I have no desire to eat these foods.

  4. What are your opinions on a vegetarian diet that cuts out potatoes, corn, and other “starchy” vegetables?

    I was raised as a vegetarian, and I honestly can’t eat meat, it looks off-putting and even it would help me out in terms of health, I don’t think I could stomach it. I do eat eggs on the other hand.

    • Harsha, no problem at all. It’s quite easy to eat like I do without meat, assuming you’re ok with eggs and dairy. You can get more than enough protein from these things (plus nuts and a few other foods). There is no need to eat meat if you are morally opposed to it.

  5. Low carbing = consuming less processed food and I have noticed that although I haven’t cooked with sugar or salt in years (except for salt on eggs) my tastebuds are really really sensitive to both salt and sugar now. I do feel that I should eat more fruit and veg but a bowl of blueberries in double(heavy)cream makes me dizzy as do parsnips and potatoes literally make me sick now.

  6. Hi Peter,
    I have been into bodybuilding style of training for about 5 years. I have some experience with high carbohydrate diet and it actually worked for me to gain over 15kg of muscle while staying relatively lean (below 10%bf).
    However, since I started the high-saturated fat medium protein low-carb approach, I achieved a more impressive degree of muscle definition, far better digestion… actually my overall health and condition improved dramatically.
    I wonder if this way of eating is optimal for further muscle gain (granted i get enough calories) despite the anaerobic type of the bodybuilding and gymnastics training. Would i benefit if add some starch peri-workout while on high-fat diet. I don’t care if i lose some definition, as i know how to cut effectively. I am more conserned about losing the health benefits of low carb eating.

    So would you recommend using insulin spikes to induce some additional anabolic effect, or you think that the Atkins approach provides an environment anabolic enough to stimulate further muscle growth?

    Thank you in advance,
    L. Stoev, 20

    P.S. I am sorry if my questions are not clear enough, English is not mother language : )

    • Stoev, no need to apologize for your English, I understand exactly what you’re asking. It’s a good question, but I’m sure I know the answer for sure, as it probably varies a lot by person, timing, etc. I would suggest doing an experiment on yourself to figure out if the added carbs and resulting insulin increase muscle hypertrophy? I think everything comes at a cost. To be as lean as possible probably makes all anabolic processes more difficult.

    • So, ingestion of protein and raising the level of blood amino acids provokes minor insulin response. Amino acid transport to muscle is somehow insulin-dependent process, while the biosynthesis of muscle protein is more dependent of testosterone and STH levels.
      Pro bodybuilders often apply exogenous insulin with the idea to rush more AA into cells. I don’t know if they actually achieve better muscle anabolism that way, but that’s their goal for sure.

      So my question is, to what extent is AA transport to muscle cells dependent on insulin? Does more insulin always means more active AA transport or there is sth like a treshold? And most importantly – are the low insulin levels still optimal for AA utilization?

      • It’s a trade-off, and it varies by person. More insulin means more anabolic metabolism (fat storage, glycogen formation, and AA synthesis). Two of these three are good, one is not. Everyone has a slightly different “dose response” also, so I can’t really give a definitive answer. One CAN still utilize and synthesize AA in a low insulin environment, however. It just may not be as efficient.

    • Yes, sugar is toxic, assuming the folks who wrote these understand the meaning of the word “toxic.” I’m not going to comment on Katz, because he fails to actually address the actual issue (i.e., the science behind the toxicity of sugar) and reverts to the standard line of “just eat more plants and sugar in moderation because a calorie is a calorie is calorie…unless it’s meat or saturated fat,” but I’m a bit confused by the paleo blog, as he basically acknowledges what Lustig and others say (i.e., dose response). What are your thought?

  7. I guess you could say I’m a moderately low carb diet person – I have a can of whole fat coconut milk as part of my fat bomb breakfast smoothie and add a banana and some frozen berries as well as a scoop of goat milk protein powder (a blend of whey and casein) and I have 2 or 3 cups of bone broth vegetable soup throughout the day as well – the rest of my diet is a pound of either raw grass fed ground beef, lamb or goat with lacto fermented sauerkraut and mustard and 4 pastured chicken or duck eggs fried in coconut oil with some more kraut and mustard and EOD a can of sardines.

    I’m also on doctor supervised testosterone replacement therapy

    My most recent blood work – blood was drawn on 3/16/12 on day 14 right before I reveived my testosterone injection and was sentg to Shiel Medical Lab

    T4 – 10.2 Ref range 4.5-10.9 ug/dL
    T3 Uptake – 32.4 Ref range 22.5-37.0%
    TSH – 3rd Generation – 2.24 Ref range .40-4.50 uIU/ml
    T3,Total – 79 Ref range 60-181 ng/dl
    T4,Free – 1.23 Ref range .80-1.80 ng/dl

    Enhanced Estradiol – 34 Ref range less than 52.0 pg/mL
    Estrogens, Total, Serum – 127 Ref range less than 200 pg/mL

    PSA – 0.38 Ref range less than 4.00 ng/dl

    GlycoHgb (A1C) – 5.2 Ref range 5.0-6.0% mg/dL
    Estimated Average Glucose – 102.5 mg/dL
    Fasting Glucose – 79 Ref range 65-99 mg/dL

    Lipids (VAP Test)

    Total Cholesterol – 324
    HDL Cholesterol – 84
    Cholesterol/HDL Ratio – 3.9
    LDL Cholesterol (Calculated) – 230

    Iranian LDL Cholesterol Calculation – 186

    Triglycerides – 54
    VLDL Chlosterol (Calculated) – 11

    Triglycerides/HDL ratio – .64

    Pattern size – A – large and bouyant

    Sub Class infomation
    HDL-2 (Large, Bouyant; most protective) – 31 Ref range >10 mg/dL
    HDL-3 (Small, dense; least protective) – 54 Ref range >30 mg/dL
    VLDL-3 (Small Remnant) – 10 Ref range <10 mg/dL

    DHEA – Serum RIA – 8.3 Ref range 1.80-12.50 ng/dL
    Testosterone, Total – 660 Ref range 300-890 ng/dL
    Testosterone, Free – 137 Ref range 47-244 pg/mL
    Testosterone %Free – 2.1 Ref range 1.6-2.9%
    SHBG – 30 Ref range 11-80 nmol/L

  8. Heard your interview with Ben greenfield and have not stopped poking around your site since. Really great stuff!

    2 questions. First, it sounds like you are not against non starchy vegetables like broccoli and asparagus, correct?

    Second, from reading your work it sounds like my issues have been subbing additional protein for the reduced carbs. I eat eggs fried in coconut oil and a bison hash for breakfast. Big salad with chicken, lots of oil/vinegar, blue/feta cheese, walnuts/pecans, asparagus/broccoli, bacon for lunch and then chicken/vegetable for dinner. I eat almonds as snacks. Sometimes protein shake with chocolate whey, oatmeal, kefir and a few raspberries. How can i get more fat and less protein in my diet? Do i need to change anything radically? I don’t react well to dairy (Hives and hayfever symptoms) so that is not a great answer for me.

  9. On your point about what is natural: sure there is an evolutionary selection and genetic modification, but does that make processed food natural?
    A can of corn vs corn on a farm are two different things and have undergone different processes. And nutritionally they differ. Can food be isolated into its macronutrient components?

    I notice you eat a lot of processed and cured meat (which is carcinogenic) and also use MCT oil and eat a few selected foods – prob limited by the fat: protein or carbs.

    Is limiting your diet to a few food choices and including processed and cured meats bad for your health in the long run?

    • I think corn in a can vs. corn on cob, notwithstanding if they add sugar to the can (which they often do), is a 2nd order term. The point is this, how “healthy” is corn? Does it bear any resemblance to teosinte (that which we evolved to eat)?
      Not sure, but it’s not actually clear the salami I eat is carcinogenic. Data suggesting this often suffer from methodological flaws of observation.

  10. I have certainly benefited from increasing healthy fats and reducing my high GI carbs. When looking at your diet I look at Salami and Cheeses as being just as processed as your corn example if not worse. I have tried to live via a “real food” lifestyle. I would love to see you put together a “real food” – found in nature diet. thx!

  11. Dr Attia,
    I saw that this was on the list of “coming soon topics,” and I apologize for jumping the gun, but I’m wondering if you can recommend any key studies or other sources addressing the vitamins and minerals issue. I’m fighting my own “war” with my fiance who is very concerned about my health given my new dietary changes, and I need some solid scientific evidence to win him over. I do have access to most major medical journals.
    Thanks in advance!

  12. Hi Peter,

    Thanks for your site…and sharing your life…..its really very much appreciated, particularly with your strong clinical background as a physician. I’m a Registered Dietitian/nutritionist, have a private practice and have been seeing clients for over 20 years. I realize RDs can invoke fear in more progressive nutrition minded people, though i think there are more and more of us who think out of the box, while also trying to maintain a strong science based approach to health. And those of us with a master degree usually have a strong background in metabolism. And Jeff Volk is an RD so we can’t be all bad :). Although I don’t know him, I did interview Jeff back in the 90;s (he and Stephen Phinney made up the bulk of my references for a protein chapter I wrote for Sports and Cardiovascular nutritionist. Based on their research I still figure protein needs for my patients based on their ideal weight and usually 1-1.5 g/kg body weight. I cringe as I read online the misrepresentation of low car diets as high protein…..really metabolically misses the boat!

    Anyway, I’m onboard with most of the low carb, mod protein, high fat philosophy and its various branches including the Paleo diet. I see a lot of celiac and non-celiac gluten sensitive people in my practice. For some time now, I’ve sort of intuitively been insulin cautious and teach carbohydrate restriction on a continuum. But a couple of questions I have:

    1. One of my concerns/questions with a 50 gram carb diet is the reduction of phytochemicals. Maybe with the reduced inflammation and reduced free radicals produced with less carbs, fewer phytochemicals are needed….but the whole field of phytonutrients is compelling with regard to preventing cancer. I understand obesity, inflammation etc. and its connection to cancer, but I wonder the risks having to limit so many phytonutrients to keep to 50 grams. I realize it does come down to prioritizing your carbs….berries and broccoli vs. lactose in milk. What are your thoughts on this?

    2. Another question is potentially the effect, if any, on the pancreas because of the high fat…..this is rarely talked about. I realize the reduction of insulin helps the pancreas in other ways, potentially preserving beta cells, and we’re talking different systems in the pancreas. But just curious, have you heard of any increase in pancreatitis etc. Pancreatitis may be the effect of other factors in a poor diet. but just curious if gal bladder or pancreas issues ever come up, considering they are the organs that help break down fat. I suppose depending on total calories, the fat load may not be an issue but with higher calorie intakes, such as yourself, was the high fat ever an issue? Ever the need for digestive enzymes?

    Again, many thanks for the effort and time you put into your blog!

    Cindy Carroll

    • Cindy, thanks for your comments. Fortunately, there are a lot of good RDs out there, too, as you point out. The fully elucidate the independent value of phytochemicals is very difficult, as there is often a confounding set of variables and, as you know, the reliance on observation is strong. That said, I think you’re getting at the right point. How necessary are their potentially protective benefits in the absence of significant inflammation, ROS, etc.?

      As far as the pancreas goes, it’s an amazing organ. It’s both an exocrine *end* endocrine organ in one! Most people focus on the endocrine part (e.g., the role of insulin, glucagon), but by mass, the cells that carry out the endocrine function are only 5-10% of the pancreas, so much more pancreatic mass is dedicated to the exocrine side, which you allude to. I see the point you are making, thought I’m not aware of long-term data suggesting it’s a problem that can’t be adapted to. It’s likely that someone immediately status post a cholecystectomy may need to ease back into full fat consumption, though.

  13. If it is of any interest, here is my recent experience with carbs and with fruit.

    On 1 June, having just turned 68 (5 ft. 10, 213 lbs) and having read Taubes and you and been convinced by the argument, I embarked on yet another low carb diet. A year ago I failed to loose weight by not only eliminating sugar (I gave that up 4 years ago) but most carbs (stayed below 20 most days for a couple of months), but I decided to give it one more shot. Perhaps, I thought, there comes a time in life that, short of starvation on a desert island or being bricked up in a basement one can no longer loose fat, period. But maybe this time….

    This time my rules were: very low carbs, 1500 calories/day (because a year ago I averaged perhaps 2300 and lost nothing; relying on my appetite to regulate my intake is, for me, a flawed strategy), and no dairy (last year I ate cheese, cream, greek yoghurt and have since read enough to raise the question of dairy in my mind, mostly from the paleo community) and no artificial sweetner, which seemed to have loomed too large in my thoughts and about which someone on this blog had interesting things to say.

    I hoped to loose four or five lbs/mo, which is about the best I have ever done in a lifetime of yo-yo dieting since the age of 14. I would eat green veg to my heart’s content, moderate amounts of meat and poultry and fish (4-6 oz per serving), olive oil, lard, coconut oil, an ounce or two of nuts, and a small amount of fruit–a few berries, the odd apricot. I hurt my shoulder badly at that time, so no gym, nothing but walking perhaps 30-45 minutes/day in various batches. I kept rigorous records.

    Results were astonishing.

    I lost 18 lbs in 6 weeks. Absolutely nothing had prepared me for that sort of result. Nor was I hungry (3 meals/day, life in between) or weak or lethargic or cranky. I know I know. I sound like one of “those” weight loss commercials, which had NEVER been true for me in a long life of trying. I figured folks were either genetically very different, or lying.

    This morning was interesting. For the first week since the outset, no loss of weight, no loss of inches.
    Looking at the last week, I exercised the same amount, ate slightly more calories than the week before (when I had lost another 4 lbs)–1550 instead of the previous week’s 1400–but the only other difference was an average of 3 serving of fruit per day (a serving being 1/2 cup of blueberries, 1/2 cup of strawberries, or 1 medium apricot) up from less than 1 per day the previous week. So it would appear that the fructose in fresh fruit is not without problems–at least not for me. Given how few calories and carbs are involved, I find it surprising. Once again, it seems to be a question of hormones.

    Like you, Dr. Attia, I am an experiment in progress. But I cannot tell you how grateful I am that you and Gary Taubes and Rob Wolf and the others are out there. I would never have stumbled on this on my own, and of course society tells me I am crazy. So I just send them to you and to Taubes and to Lustig and I continue to loose weight. At my age this is a matter of life and death. I owe you.

  14. One question: in books by folks such as Dr. Fuhrman, Esseltine and so on, they recommend a mostly plant-based diet, based on the notion that plants contain huge amounts of valuable micronutrients – phytochemicals and such – many of which have positive benefits for humans. According to these experts, we are discovering every day more and more about these micronutrients in vegetables and their health benefits. Dr. Fuhrman posits a high nutrient-dense diet consisting heavily of plant foods and small amounts of meat, claiming it’s much better for you. In truth, I’ve noticed that a food such as kale is very high in nutrients. How do you reconcile such “plant-based” experts with the low-carb recommendations?

    • Tom, it’s really a question of scientific evidence. Where is the clinical data — not mechanistic or “intuitive” explanations — that phytochemicals are necessary for health in the doses suggested by some? I’m not saying a eating vegetables is bad, but I have not see real experimental data proving it’s necessary. Many of the proponents of this (Esseltine, Campbell) rely on observational epidemiology to make their case, but we can’t confuse this type of work for experimental science. I have to recommend you devote some real time to this, and there is no better place to start than Denise Minger’s work on this topic, which you can read here: http://rawfoodsos.com/2010/07/07/the-china-study-fact-or-fallac/ and here: http://rawfoodsos.com/2011/09/22/forks-over-knives-is-the-science-legit-a-review-and-critique/

      I know what you’re thinking…this guy wants me to read for the next 4 hours? Yes, I do. If you’re serious about learning this stuff, you’ll need to be serious about understanding the lack or presence of the scientific method used in espousing such recommendations. Only when you do this can you make an informed decision for yourself.

    • Peter,
      I’d find it very helpful to have an FAQ that gives a clearer explanation of how you choose the vegetables and fruit that you eat.

      I can see: the pictures of raspberries, avocado, and green salad, and references to these in the example meals; references from other people in comments to starch free items like broccoli; examples you list of fruit and fruit juice that you don’t recommend; negative references to peas; etc. However, what is the criteria and how could we check it?

      Thanks for the site, and for the balanced way that you and the team are approaching this. It’s all new to me, but I’m impressed and grateful!


  15. Hi Peter,
    One of the reasons I eat lots of fruits and veggies is for the fiber. When I low carb I get constipated. Aren’t fruits and vegetables important in a diet for their fiber content? Also what is your position on legumes here?

  16. @Peter

    If you believe that we should eat a diet like our paleo ancestors – correct me if this statement is untrue – then why doe you consume so much dairy?

    How far back on the evolutionary time scale should we go to determine what we should or should not eat? 10,000 – 100,000 – 500,000?

    After all – dairy is not paleo. Lactose tolerance only developed within the past 7500 years or so.


    Breakfast: “Fat shake” (In a blender: 8 oz heavy whipping cream, 8 oz sugar-free almond milk; 25 gm sugar-free hydrolyzed whey protein, 2-3 frozen strawberries)

    Lunch: About 4 or 5 oz of assorted cheese (Gouda, Swiss, Manchego), 2 or 3 oz olives, about 4 oz of particularly fat salami and pepperoni

    Breakfast: Scrambled eggs (6 yolks, 3 whites**, with added heavy fat cream) cooked in coconut oil, 3 or 4 sausage patties (be sure to look for brands not cured in sugar).

    Coffee with homemade whip cream (heavy fat cream hand whipped)

    Lunch: About 4 oz of especially fat salami and pepperoni, about 2 oz Parmesan cheese

    Dinner: Ground beef sautéed with heavy cream, onions, broccoli, and melted cheese

    2 large cups of decaf coffee with homemade whip cream (heavy cream whipped with a touch of xylitol)

    • I used think I was profoundly lactose intolerant and avoided dairy like the plague. Interestingly, once I removed wheat and most fruit from my diet (I only eat modest amounts of berries), voila, I’m not lactose intolerant. In reality, I doubt I ever was.

  17. Peter,
    Since we’re borrowing on Lustig in this blog post we should also mention he absolves the fructose contained in fruit with his quote, “When God made the poison he packaged it with the antidote”. This is a reference to the fiber contained in fruits & veges which offset the ill effects of fructose.

    Fiber aside I refuse to believe the fructose content in something like a carrot or handful of blueberries carries the same toxic punch as the same dose of granulated sugar or HFCS…I’m just not buying it.

    • I know Rob personally. I can assure you that he does not view peas, carrots, and blueberries in the same category sucrose or HFCS, even molecule for molecule of fructose. That’s his point.

  18. Am I wrong to be annoyed when Lustig keeps trotting out easily misunderstood slogans such as “eat real food” and appealing to nature fetishism or beliefs in a benevolent god (e.g., “God would never give us anything bad”)? Obviously he’s not telling his patients to drink lots of “natural” fruit juice or to gorge on God’s gift of honey, and he often provides examples wherein fruit consumption causes adiposity.

    So I’m really curious about why he takes this “eat real food” tack. Is God and nature his way of selling his message to Americans? Is exchanging Twinkies for watermelon some kind of compromise position?

    BTW, I’m really not trying to run Lustig down. Most of what he does is awesome. I just think your message (and that of Taubes) is both clearer and cleaner, and I don’t understand why Lustig can’t do the same.

  19. Peter,

    This post is an example of what is driving people crazy. You seem to be a sincere and well-meaning man, but your writing could stand to be cleaned up.

    For example: “Most people assume the fruits and vegetables we eat are “natural,” but in reality fruits and vegetables of today bear little, if any, resemblance to their original form” is a meaningless sentence. There is no such thing as an “original form” of an apple. I get the point you are trying to make: that since the AR, we’ve been developing strains of fruits and vegetables that are higher in sugar content than in the past, but the sentence is meaningless.

    Second, and this is the more overarching point, the beleaguered public listens to people like you and turns off because you are not making clear that eating fruits and vegetables isn’t the same thing as eating fat-carb bombs full of refined carbs and sugar. An apple is NOT the same thing as apple pie.

    Does your wife eat lots of desserts, refined carbs, etc? or does she eat “sugar” in the form of fruits and vegetables?

    Did you see this?


    Do you really think that eating apples has the same metabolic effect, and the same effect on the gut flora, as eating apple pie?

    • I think you’re missing the point, Diana. At no point have I suggested an apple = apple pie. You may be confusing something else or taking commentary elsewhere out of context. When I talk about not consuming fruit in an unlimited manner, it’s in the context of nutritional ketosis. If one wants to be in NK, one can’t have too many apples. As to your question about the NY Times article, yes, I’ve seen it, though reading the NYT for ‘science’ is pretty limited. You’ll get more out of reading the actual paper by David, who I know very well and have been discussing this point for about 12 months.

    • “As to your question about the NY Times article, yes, I’ve seen it, though reading the NYT for ‘science’ is pretty limited. You’ll get more out of reading the actual paper by David, who I know very well and have been discussing this point for about 12 months.”


      This was a horribly condescending thing to say. I don’t have access to the entire paper. I read the abstract, the full item “requires a subscription to The American Journal of Clinical Nutrition.”

      Does it really make a difference? Did I point out something incorrect in citing the NY Times blog item? Can we agree that sugar addiction is real, and that apples don’t contribute to it?

      Regarding the rest of your points, let me hasten to add, I AM ON YOUR SIDE. I get what you are trying to do. I just don’t think you are making your points well, sorry.

      You go into a long explanation about how fruits today aren’t the same as fruits 10K years ago….then you admit that apples aren’t the same thing as apple pie. But the way you phrase it, you make it sound as if modern apples are unhealthy, because they have been bred to be big and sugary.

      Like it or not, this is the message you are propagating. Sugar kills, fruits have sugar, don’t eat fruit.

      Do you want to communicate with more than just an elite few? Or do you want to communicate with the general public?

      • Diana, first off, I appreciate your support for this issue and your point. I think something is being lost in translation. I do not disagree that fruit is not equal to sugar. I am very if my point about reading that article came across as condescending. This was not at all my intention. I was trying to make a broader point that it is nearly impossible to glean from a newspaper, even a reputable one, the truth in a study. In this particular case, the writer (Anahad O’Connor) did an excellent job reporting on the outcome and implications of the Ludwig study. This caliber of reporting in the press is the exception, not the rule. Anahad is, in my opinion, the most reliable science reporter on nutrition. Regardless, I see your point. I apologize for offending you. Not at all my intention.

    • Peter,

      No problems. I agree that science journalism on the topic of nutrition is mostly awful. The NY Times has great science journalism, IMO (Nicholas Wade is awesome), and this particular article was great because it had an interview with the scientist.

      It is true that eating too many carbohydrates – even good ones – will inhibit lipolysis. In fact you might say that that is the purpose of eating carbs and this was a good thing back in the day when people were skinny animals hunting other skinny animals and we needed fat. It’s not so good now. If you have to lose fat, you must control carb intake, including fruit.

      But you don’t get fat eating fruit. This is not the way we get fat, sorry. People are binging on huge amounts of junk food and no one wants to call them on it. I got fat that way, and I got relatively lean by cutting out that behavior pattern.

      I walk around where I live, NYC, where people are supposedly thinner than in most of the rest of the country, and I am seeing obese young people (mostly but not all young women) and it kills me.

      That is why I am very fanatic about good information getting out there, to the general public. They need a simple clear message. Not dumbed down, but simple and clear.

      Confusing the issue with disquisitions about what apples were like 7K years ago is not the way to go. Look at modern American’s (and Brits and everyone else’s) food intake and you’ll see a lot worse than some fruit.

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