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. Quick question Dr. Attia:

    A lot of what we “do” depends on accurate measurements.

    For one, we know that many of the “measurements” taken at most of our primary physicians are based in flawed science (to a degree).

    When, in you opinion – will the medical industry truly produce a scale or measurement that will help the common public? I could detail what that would comprise of – but you SURELY know what I’m talking about.

    We have SO MUCH TECHNOLOGY that is SO ADVANCED – you’d think that the so-called “tests” would be lock-step with such advancements. But they ARE NOT.

    Can we peek into this a bit?

    • Sure, you can’t treat if you don’t know where you’re starting from, which requires measurement. The biggest single flaw right now is in lipid testing. Too many docs treating LDL-C, rather than LDL-P. I’ll write a great deal about this in the coming months.

  2. I find it interesting that most people consider vegetables, and fruits to a lesser extent, to be the ideal food that all humans should eat. Michael Pollan’s “eat food, mostly plants” is a perfect example. It runs counter to what we know about human evolution. The ability to hunt and eat meat is what set humans apart from the other great apes. There are many populations throughout history that have survived on zero plant diets and have been perfectly healthy.

    One of my great interests is anthropology. From all the lectures I’ve been to and books I’ve read on it, everything points to humans as meat eaters. If you think about it, what is a better quality, more nutritionally dense food, a few pieces of fruit or a few strips of meat from wild game? There’s no question that the meat is the better food. It’s more calorically dense, it contains more vitamins and minerals, and far more protein than any plant. This is why our ancestors evolved the way we did, so that we could go after better food: meat.

    Unlike most predators, we don’t have speed, fangs, or claws. However, we do have species defining characteristics that make us great hunters. Bipedalism, lack of fur, and sweat glands gave our ancestors the ability to run down fur covered quadrupeds in the hot sun. We certainly didn’t develop these tools to run down bananas. If we evolved to eat fruit and plants, we would have stayed in the trees like the other apes, or stay on all fours like baboons.

    We’re meat eaters. We should embrace it. Plants are fine, but they’re not the ideal food for our species. Like Taubes, I doubt if they’re even necessary. I’ve gone for week long stretches myself, to experiment, eating just meat and dairy and have seen no ill side effects. I know there’s been observational studies of populations that eat no plants, but I wonder if there has been any clinical studies on whether or not plants are necessary in the diet.

    • Just watch Survivor Man (Les Stroud). When he’s dropped into the reality of nature, no readily available plant substance can provide enough calories for a modern human. (Well, there was one episode on island survival where he kept eating coconuts.) You can’t even rely on small game, unless boiled to extract the fat from bone marrow – see “Rabbit Starvation” on Wikipedia. That right there is a prime example of how much we depend on calorically-dense fats, and should be a clue for anyone trying to understand a “natural” human diet.

    • I disagree completely. For years I have researched scientific journals and read books about nutrition from many different standpoints in hope to find the most “ideal” lifestyle. After reading Dr Campbell’s “China Study” (The book that every vegan points to!) I finally was convinced that the vegan diet seems to be the most beneficial. I suggest you take a look at it if you’re open minded enough to get through it.
      As for my own personal experience, becoming a vegan has cured many of my little health issues, such as irritable bowel, acne, frequent stomach aches, and headaches. I have also had unexplainable eye pain in one eye for the past 7 years, which completely went away after going vegan, something I never would have expected to happen simply from changing my diet!

    • Emily, just because you have read several books and have moderate success on a vegan diet does not mean everyone else has the same experience. 2+2 is 4 but so is 5-3, so to assume your solution is the only one is a bit thick. Most vegans do not stay vegan for life because it is such a hard lifestyle to maintain without dealing with gastrointestinal issues down the road (I am speaking from actual experience and real human beings not a book) , and only the very dedicated manage. Vegan living is an amazing lifestyle but one that an individual needs to come to on their own terms. Not sure how one can disagree completely with a person’s individual experience but ok.

    • There are also hundreds of millions of people who do not touch any meat throughout there life and are perfectly healthy !

  3. Peter,
    You and Gary (as well as many other hard-working low-carb bloggers) are becoming LCHF rock stars!

    Please continue to use the diagrams and pictures. They are extremely valuable when you are trying to reach an aging, diabetic father because the message is more direct and succinct. I am sure you are aware that Dr. Eenfeldt posted a nice “poster” on how carbs make you fat. I find these types of charts/diagrams/pictures very far-reaching in terms of audience.

    Also, are there any diagrams out there showing fruit on a scale of least to most sugar? Perhaps such a diagram of certain fruit today superimposed over a diagram of that fruit, say 100 years ago, would tell a good story?

    Words cannot express the gratitude I feel for the information this blog gives me access to!

    • Michele, thanks very much. I don’t know about being rock stars — I’m trying to stay below the radar, actually, since blogging is a very part-time endeavor for me. I don’t know of a diagram as you describe it, but it could certainly be done. One (easy) way to do it would be rank by GI, but I actually think that would not be the most useful way to do it.

      • I had forgotten the site sugarstacks.com…I cannot remember if I found this through your blog or one of the other blogs you read. Either way, this is not a diagram, but shows the sugar-content in fruit in terms of stacks of sugar cubes, so a step closer to the diagram I’m looking for:


  4. Two edits:
    1.) Discussing your wife’s sugar response you write, “…, should could eat unlimited amounts of sugar…”
    2.) Discussing corn yields, “…200 bushels of corn per acre per year, up from less than 20 acres per year…” (Should be 20 bushels per acre per year.

    Onto my questions. Did you happen to read Denise Minger’s post a few months back about the fructose content of wild tropical fruits? They were surprisingly high, and she claimed they were eaten year round, or close to it. Do you think refined fructose is singularly capable of causing metabolic problems, or do you really think its just a matter of dose, keeping in mind the often pointed out fact that it’s easier to drink a glass of orange juice than to eat eight oranges?

    I’ve also recently seen more and more people claiming that vegetable oils lead to inflammation and metabolic problems, and that only with this trigger in place does carbohydrate consumption cause trouble. I don’t buy it – I think there’s compelling evidence that excess fructose alone can cause obesity, type 2 diabetes, etc. But do you think there’s any validity to the idea that the consumption of certain oils might contribute?

    Thanks for the great post.

    • Garth, thanks for the fixes. Got ’em. Great questions. Yes, I did read Denise’s post on this topic. As you probably can tell, I am a HUGE fan of Denise’s work. I think she is simply so smart and talented. I don’t actually think my post is contrary to hers, if you read both carefully. Sure, we may disagree on the margins, but I think our point is similar. When you read Denise’s post, and juxtapose it to mine, keep a few things in mind:
      1) While I use corn and Fuji apples as examples where size is an obvious morphologic change, there are many other subtle difference, as Denise points out (e.g., pulp, water content).
      2) Even though some (not all) prehistoric fruits may have had a modest concentration of fructose, it doesn’t tell us how much of said fruit people ate. Remember the dosage issue of fructose (and ethanol) — there is a very different metabolic outcome from consuming 20 gm/day versus 140 gm every 7th day. Dose and timing of dose really matters.
      3) It’s not actually clear how many folks were consuming large amounts of fruit in ancestral times. Certainly pockets of people may have been, depending on food availability, but it’s not clear this was a ubiquitous practice.
      4) TTX existed a million years ago, too, so my other argument is still important. We can certainly discuss exactly how much fructose was in the fruit, but the larger point remains — the presence of fructose does not mean is was (and is) “good for you,” especially in the quantities we consume today.

      To your second question, the high omega-6 oils (big 4: corn, safflower, sunflower, canola) are pretty horrible, especially in the quantities we consume, coupled with the dearth of omega-3 we consume. As to whether this, alone, is the root of our metabolic problems I don’t think we can definitively say, but I don’t think so. I think it’s an amplifying factor. In other words, n-6 to n-3 imbalance, coupled with high sugar/high carb consumption create a more-than-additive impact (deleterious, of course) impact on metabolic syndrome.

      • To your point #3 – it is also possible that some peoples ate large quantities of fructose rich fruit and lived short, sickly lives because of it, but that could be better than the alternative (starvation). If the choice is between eating a bunch of sweet fruit or nothing at all during a dearth of other food options I believe most people would choose to eat fruit. The consequences of fructose consumption generally don’t seem to impair fertility enough to cause a strong evolutionary pressure against it. Starvation does provide a pretty powerful selective pressure. I have no idea if this hypothesis is a possiblility, but it strikes me as worth exploring…

        • Excellent point, Edmund, and I was actually thinking of this after I replied (while swimming this morning). If people look back at today in, say, 10,000 years, they will note that we had Snickers bars. But what can they conclude if they see no other information? Could they conclude Snickers bars were “healthy?” Nope. In fact, they could hypothesize (thought not conclude) that the population subsiding on Snickers bars did WORSE than the population not subsiding on them.

  5. Great post, Peter. So clearly written and backed up with undeniable stats that there is no question sugar is a huge culprit in our present health crisis!

    Can I ask a general question about thyroid and low-carb eating? It has been puzzling me. I’ve just been diagnosed with low-thyroid (on a scale of 0.35 to 5, I’m at 6.20). I’m taking meds for this.

    Under these conditions, in general, is it wise to stay on a higher fat, lower protein, low carb regime? Or should one eat a bit lower in fat so as to maintain weight until the thyroid is more in balance, then up fat once more?

    I know you don’t want to get into personal medical stuff – but just as a principle? There are so many folks out there who struggle to get thyroid balance – and many eat low-carb and get stuck!!

    • Glad you like, Barbara. I will address the thyroid-carb issue in a subsequent post, and I’ve got it on the “coming soon” page. It might take a while, though. You definitely need to have your doctor help you with this.

    • Hello Barbara,
      I am hypothyroid as well (my thyroid was removed, I hover between 0.37 and 2.00 – also “normal”). I am not a doctor but from my experience, if you are stuck it is due to your TSH and potentially one of the other related values (FT3, FT4). Until you sort out your dosage of hormone, eating more fat and weight training will help if only so that you do not gain more weight. Peter has mentioned the dangers of too much protein (which I have found makes me gain weight when I eat too much AND my thyroid values are not correct). I hope this information is helpful.

  6. I was a vegetarian for 10 years or so, and interestingly enough, I think my vegetable intake has gone up on my LCHF, ketogenic diet. The simple reason is that before I would eschew the salads and choose low-fat, grain- based foods like rice, pasta, and bread as my staple. If not grains, then legumes, although that probably does class as a vegetable. Anyway, now the salad is my go-to option for many meals (topped with lovely bits of meat and cheese, of course). And might I add, broccoli and butter love each other.

  7. Peter, nice post, and I agree with you 100%. However, I think there’s one point you’re not considering when you look at the recommendations from someone like Michelle Obama (I’m not including the USDA in this, since I believe their interests are entirely commercial), and that is, “the best is the enemy of the good.” Given the horrific state of the standard American diet, eating more fruits and vegetables, and even whole grains instead of refined ones, would certainly be a big improvement for the vast majority of people, even if it’s not the “ideal” diet. The problem we face now is that our current way of eating is no longer just a diet, it’s a culture. It’s embedded in everything we do, and in who we are. I think many people are past the point of no return when it comes to what they’re willing to sacrifice in their diet, particularly since many of them are now “habituated,” if not outright addicted, to sugar and starch.

    You face an uphill battle getting your message across. People believe things because they want them to be true, or because they fear that they’re true, and in this case, people desperately want to believe that sugar and starch are necessary, healthy components of the human diet, and they fear that the calories in/calories out model is correct. Add to that the huge commercial interests at play, the primary sources of funding for nutrition research, and the sheer volume and conflicting nature of “noise” in the media and on the internet regarding diet and health–and it seems next to impossible to create the sea change we in the low-carb community would like to occur. That’s not to say you shouldn’t fight the fight. Perhaps it will take a grass-roots movement like the one happening in Sweden (and led by people like you) for that sea change to take hold here in the U.S. But I believe high-profile figures like Mrs. Obama, Dr. Oz, etc. believe they can affect broader change by introducing more incremental adjustments to the diet that are “politically accepted,” and it’s not clear to me that they’re wrong.

    • Lisa, you are absolutely correct. I hope I don’t suggest that Mrs. Obama or others are doing anything nefarious. On the contrary — they really want to help, and to your point, if the choice is between potato chips and a candy bar versus more fruits and veggies, it’s a no-brainer. But it doesn’t change the much broader and more important point (which is why we are forming NuSI): It’s time to put some science behind nutrition guidelines and food-based policy. I certainly have a hypothesis for what is right and what is not. But I could be wrong. Let’s stop the dialog and start the real science.

    • Lisa, I think you have a good point. When there’s nowhere to go but up, even small improvements are — well, improvements. I’m reminded of a friend of a friend who bought an old house in a poor neighborhood. She said most of her neighbors don’t even have stoves in their kitchens. There is little food preparation at home. People eat only the packaged stuff they purchased at the local store, and often as not that’s things like chips and candy bars.

    • Americans are not going to eat whole grains. Just forget it. I made mostly righteous whole grain bread twice. it was from freshly ground wheat, but I did add sugar (for the yeast).

      Can’t see anything but a very marginal improvement in the whole grains. The Chinese who were poorest didn’t get beri-beri but the next group that could afford white rice did. However, the next group up who could afford a little Chinese Cabbage with their rice did not get sick.

      Or mayhap the SAD is that sad.

  8. Dr. Attia,

    You’re leading me (perhaps unintentionally) to give up my daily “medicinal” alcohol permanently, which is good news to me, since I cut it out temporarily a while back to lose weight and still wonder if that is extreme or even ill-advised.

    Does anyone suspect that the apparently well-documented benefits of low daily alcohol use are minimal to LCHF people? The commercial interest driving that research would seem incredibly strong. Have you developed an opinion yet on whether the benefits of moderate daily alcohol vanish if one does LCHF? Or any research I can dig into on the subject?

    Not to neglect the central point of this excellent post. Sugar is long-gone from my diet, thanks to Gary Taubes, confirmed by your work. I’m grateful to you for this post, because I’ll be able to refer many friends here to help exorcise the “natural” demons efficiently.

    Thanks again,

    • Fritz, as much as I LOVE my glass of wine with dinner a few times per week, I’ve never seen convincing data that it’s actually GOOD for me. I could argue that at small doses it’s not too BAD for me, though, which is what I do argue.

  9. Wouldn’t it be great to really know what our ancestors ate? There is some archeological evidence, but it doesn’t seem as thorough as it could be. I’ve seen human evolution documentaries where bone protein analysis was done on Neanderthal bones, and they determined they ate no substantial amount of plant protein. They neglected to show the same results for Homo Sapiens bones. I would be interested to see those results. I’m sure there were great variations in diet based on what was available regionally. I got a great lesson in this a few years ago. I live in a climate that is similar to my ancestral climate. Cold, northern, little sun. I subscribed to a year round CSA. In my area the only plants that are available for 7-8 months out of the year are leafy green vegetables, mushrooms, and some really sad overwintered root vegetables. Fruit is only available for 3-4 months, and each fruit is only available for a week or two. We have become very disconnected from how food actually grows because we can buy bananas and apples every day of the year. I would guess that most of us would have no deleterious effect from fruit if we only ate it when we could actually pick it and put it directly in our mouths. Consumption of fruit would certainly fall. The other lesson the CSA taught me was counter to Pollan’s mantra about mostly plants. If I ate mostly local plants I would quickly die of starvation. So would anyone else who live in a climate with harsh winters. Food for thought!

    • Boy, Helga you certainly hit the nail on the head with your post. I too live in a cold climate, and to add insult to injury, what the squirrels don’t get the rabbits sure do. We could live off those furry little creatures, and pigs and chickens, and whatever greens we could grow, and the fruit that does well here – and then there are the lovely deer, and moose, and farther north, the caribou etc.

      But to eat tomatoes from Mexico, tender greens from California, grapefruit from South Africa, grapes from South America….well that seems a little crazy. Maybe the local food movements are the way to go – but as you say, limp carrots, dried out rutabaga, and mouldy squash does not appeal in February!!!! What about hydroponics? Is that the answer?

      • I think not feeling like you doing the wrong thing if you don’t eat large amounts of fruits and vegetables every day is the answer. Don’t get me wrong, I enjoy these foods. But like exercising, I do it because I like it and not because I think it’s going to make for perfect health.

    • I had my DNA mapped, and my ancestors are all from Europe going back 10’s of thousands of years. That time period includes the last ice age when I doubt they ate much fruit at all, and vegetables maybe only a few months out of the year, if they even bothered. My hunch is my genetic make-up is not suited very well for carbs.

  10. Hi Peter,

    I think this is a great post, your points about what is and isn’t “natural” are absolutely spot on. I do have one concern. I see no reason to paint vegetables with the same broad brush as fruits. One can eat MOST vegetables and get nowhere near a problematic level of fructose. One can only eat a few fruits, by contrast.

    It’s a great idea to eliminate high fructose or high GL vegetables like corn and potatoes from our diets… but there are a great many vegetables that are perfectly fine and healthy to eat, that don’t adversely affect insulin and have the benefit of adding vitamins, minerals, fiber and – a point not to be excluded – more variety to a truly healthy diet, which helps to change it from just a diet to a lifestyle. “Limit fruit and vegetables” is, in my opinion, much too broad and sweeping a statement (i.e., the title of this blog), without qualifying it to mean most fruits and some vegetables.


    • Conni, you are absolutely correct! Of course, if I try to explain everything, my already-too-long-blog-posts turn into, well, you know. The nuances you’re describing are very important, and when given enough time, I like to communicate them, also. Thanks for helping me out. The important point is that folks need to evaluate each food type individually and within the context of their own genetic predisposition. All fruits are not created equal, either. While I don’t eat Fuji apples or bananas, I do still eat raspberries, blackberries and strawberries. HERE IS THE IMPORTANT PART, though. I don’t eat them because they are “good for me” or “necessary” for good health. Same holds for salad. I eat salad because it’s an awesome way to eat fat. I eat berries, because they are a treat.

      • I’m very glad you saw it as helping, and not nitpicking, because that was my intent – helping to keep the message clear. There are more and more people every day getting interested and trying to understand what they’re supposed to eat, and it can be confusing in the beginning. My husband and I do eat apples – but we split them, and each have a half. Tastes great with pork sausage for breakfast. Keep up the great work, and thank you.


  11. One should not that without the ability to increase yield on farm land and for agricultural products, over at least the last 100-200 years, the planet population would most likely NOT be able to sustain itself.

      • I’m not really sure I understand the question? But, here are some data points.
        In the last 200 years, population has risen from roughly 1 billion to over 7 billion. That’s a lot.

        50 years ago, crop yields were increasing roughly 3.5% a year, which was comfortably more than a global 2% population growth. But, today that number is closer to 1.5%, just about the rate of human population growth. When the production growth rate goes below the population growth rate-that’s when the problems will begin. not to mention the fact that VERY LARGE percentages of the worlds population-specifically 3rd and 2nd world are moving to consume ever greater quantities of foods stuffs, far more than they did in that past 20-30 years.

        I’d love it if WE ALL consumed less, across the board. It would probably do everyone good. I’m concerned, however, that without continuing growth of production we could run into a commodity production wall and demand spike. Historically, that hasn’t proved a good environment for populations.

        • Yes, agree with your analysis. I’m just asking a broader question: Are we (humans) better off with a planet of 7 billion people, some large fraction of which are not healthy? I don’t know the answer, actually, or even have a strong point of view. Just an observation. Think of an extreme case: what is better, X people living in perfect health or 10X people living in misery? I don’t know that the number of people is the best metric. What about quality of life?

    • We have no idea what would have happened if we had not added all the technology to farming. And I’m wondering if the tradeoff was worth it. We’re doing our best to reduce the population (in fact Europe is past the tipping point in that it will NOT be able to sustain itself in 50 years) and we don’t seem any better off in any areas of measurement!!

    • Following along the thread of emerging 3rd and 2nd world consumption habits. Wouldn’t it be great if the 1st world could mentor them about the mistakes we’ve made, and help them avoid the pollution and obesity issues?

      All the more reason to really work on the science and figure it out sooner than later. :o)

  12. Thanks for addressing the “natural” fallacy!

    At the moment I’m reading “Wheat Belly,” and the author makes some interesting speculations about how repeated hybridization has changed the wheat genome so much that its gluten proteins are quite different from those of its ancestors, einkorn and emmer wheats. I imagine the same thing could have happened with corn – after all, the ancient peoples of Mexico called themselves the “People of the Corn” and didn’t die out from eating it. Is there any way to find out how much the proteins have changed with intensive selective breeding, and whether those changes ARE actually harmful, except by observational studies?

  13. I’ve always considered the all-wild-fruits-were-tiny-and-sour idea to be somewhat of a myth. If you’ll Google “wild plums” you’ll see some good information, with pictures. When I was a kid, we had wild plums growing on our farm in Nebraska. Yes, when they weren’t 100% ripe, they were hard and sour. (So anyone with the preconceived idea that all wild fruit was hard and sour could easily find “proof.”) But when fully ripe, those plums were the sweetest, juiciest, most succulent fruits you could ever imagine. Nothing in the grocery stores today even comes close. I’m sure there were other wild fruits just a wonderful.

    • Perhaps. But it doesn’t change the point I’m trying to make. Just because it tastes good, does that mean it’s good for you? Does it mean eating it (now or 7,000 years ago) improved health?

        • Leave it up. I think my point was missed as well, and maybe I need to be more specific. My point is that although most of the current “wisdom” that I read about wild fruits states that they were small and sour, I happen to know from personal experience that that observation isn’t completely accurate. Generalizing from that: I think we need to be careful about drawing hard and fast conclusions about much of anything, since in most cases we probably don’t have all the information.

          Do I think eating sweet wild plums would be detrimental to the health of a person 7000 years ago? Again based on my personal experience, I’d say that eating sweet wild plums once a year in the years the plums didn’t freeze would probably be insignificant one way or another.


    • Marilyn, I hope you decide to leave your comment, because this is something I’ve thought about also. I believe that you’re right, that there were fruits that were deliciously sweet before they were genetically modified. It is worth noting that in many climates, these fruits were not available year-round. It’s quite likely that our ancestors very much enjoyed eating these sweet fruits when they were available, and also quite possible that they put on a few extra pounds as a result. Those pounds probably came in handy to burn as energy during the winter months. I also think that the availability of fruits year-round in some climates could have caused those populations to evolve differently. It would help explain why some of us can eat more carbs than others, and maintain comparable health. Who knows what genetic soup we’re each handed?

      Your comments are quite valid, and a worthwhile part of the conversation. I think. 🙂


  14. Hi Peter
    Can you help me with something. I am fairly evidence driven, and hold others to the same standards I hold myself.

    Having said that, can you help clarify something? When you invoke apple eating and use terms such as “toxic” and “harm”…

    At the macro level, I know exactly what you mean (sugar, fat, etc). However, I am unclear how an individual assesses toxicity in the context of a varied diet, using foods that might comprise <10% of daily caloric intake. Tall order, especially without elegant measurements and daily diet tweaks beyond the capacity of usual and customary.

    More a theoretical discussion than practical, no?


    • Sure, Brad, but don’t think in terms of caloric input. If you got 10% of your calories from certain wild mushrooms, you could also be causing significant toxicity. Same thing with ethanol.
      I don’t think % of calories occupied the food is the best metric to assess. There are no calories in tylenol, yet 10 gm would destroy your liver.

      • I was using % calories only for illustrative purposes and as a stand in. Another way of saying it–these items (like fruit), only comprise a fraction of our diet. For someone like yourself, and I would include myself as well, dietary regularity with minor changes might give useful signals, ie, what is “toxic” and not. Although, even as a I write this, I dont know if I can identify these signals. Feeling “low energy today” does not count.

        However, most folks cant utilize that kind of instruction to determine “toxicity.” How can individuals determine if an apple is good or bad, or cherries, or peanuts, etc.

        Hope its clearer


  15. Great post. The Laura Schmidt’s article you referred to claims that high sugar consumption can lead to fatty liver disease. I have already had a fatty liver (and other metabolic syndrome symptoms) when I started my ketogenic diet a few weeks ago. One of my concerns is whether the fatty liver won’t get worse with a fat rich diet. Is this a real risk or, to the contrary, a ketogenic diet should improve the condition of my liver?

  16. Dr. Attia,
    I can’t recall if was you or Gary Taubes who noted that when tribes who are isolated from civilization have been studied by anthropologists they found that their preferred foods were animals and the choice parts were actually the organs. So I definitely think this view of the sort of “noble plant eating savage” is more fiction than fact. I have noticed after reading a lot of different diet and nutrition books in most of them the common thread is to drastically reduce or eliminate white flour and sugar. The problem is in a lot of cases the authors expand their scope and attack every aspect of the Western Diet with minimal evidence to justify it. (It would be like a fire investigator blaming everything in the house for the fire rather than just the candle left burning). When I read the books “Eat to Live” by Joel Fuhrman and “In Defense of Food” by Michael Pollon I get the impression that these two authors were in favor of plant based diets going into this and are trying to find evidence to prove it to be true. Where as in your and Gary Taubes case you didn’t have any preconceived preferences going in you were just trying to determine what the evidence was and where it lead. Unfortunately I think a lot of scientists have gotten into the business of making a hypothesis and trying to find evidence to prove it rather than refute it.

  17. The key question seems to be: “What did our ancestors eat while their genome was evolving?” This can then be contrasted to the standard North American diet.

    I actually posed this question to a retired anthropologist in my clinic. He stated that our paleolithic ancestors consumed a diet consisting of at least 80% meat, and surprisingly, most of it was in the form of carrion (dead animals or carcasses on the ground, particularly small furry mammals such as squirrels and the like). We had such a limited tool set that we could not really carry out much in the way of agriculture or vegetable growing – essentially what we had we used to scare off other scavengers by throwing rather hard, solid, sharpened objects at them, so we too could dine at the feast. I don’t know if this is the latest consensus academic opinion – my informant retired a number of years ago. But it does pose a marked contrast to those who state that we subsisted on a fruit/vegetable/grain diet.

    Just thought I would share this as it may be interesting for your readers.

  18. Apples are a good example of selective breeding concentrating a trait in plants, in this case sweetness, i.e. fructose. Potatoes are another good example – They are much maligned in Paleo circles, and in my opinion some of the bad mouthing should really be directed at the variety grown less than the generic crop. I never enjoyed potatoes on my plate until I grew a high protein variety in the home garden. There are varieties of potato that lay in large amounts of protein (about 1/3 by weight), but one almost never finds them in a supermarket for two reasons that I can see.

    1. Building proteins is more metabolically taxing than building carbohydrates. That disadvantage means the yield of a carb rich crop will be higher than that of a protein rich crop, all other things being equal. Since farmers are paid by the volume they grow not the quality, the incentive is to grow whatever variety provides the “greatest” yield, not what promotes the greatest health.

    2. Protein rich potatoes do not keep nearly as well. No middlemen want to be stuck with a truckload of rotten potatoes, so they too exert pressure on the system toward the carb rich, flavorless crap on offer at your local neighborhood store.

  19. I think one of the main myths of the “vegetables are healthier” argument is that they are “full of vitamins and minerals”.

    If you compare a 3 ounce serving of any lower carb vegetable to the same size serving of beef or pork, the vitamin and mineral content of the meat is much higher. But you don’t hear how meat is “full of vitamins and minerals” very often.

    • Yes, and I believe there is evidence that a low-carb diet allows the body to use the vitamins/mineral better. I seem to remember Taubes specifically mentioning calcium as an example. Wouldn’t be surprised if Peter has post on this somewhere (or in the works), since he’s a blogging machine.

      • Matt, you are correct, but I have not yet explicitly written about this. Vitamin C is a great example of this. In the presence of glucose you require a great amount as a co-factor for the amino acid proline, but in the absence of glucose, you require a fraction of the amount. Hence, I consume virtually no vit C, yet have no scurvy.

    • Peter,

      The sooner the post on this vitamins and minerals issue comes the better, as that is the most frequent argument I get in response when talking about your views with people who find them outrageous. Specifically, that we “need” to eat fruits and vegetables (and to some extent complex carbs/whole grains) for the vitamins and minerals they contain in order to be healthy and not die of some other problems separate from the metabolic disease associated conditions. I know there is a a difference between fat soluble vitamins (found in animal products and some oils) and water soluble (found primarily in plant-based sources), but I don’t have enough information about this to explain why you don’t “need” to eat fruits and vegetables and whole grains.

      • I will get to it. But in the interim, everyone time someone *insists* that you need X or Y in your diet, just ask them to show you the data? Simple request, right? I need X mg of this or Y mg of that. Great. Where did that recommendation come from?

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