The top 3 dietary causes of obesity & diabetes

donut

So far in this series we’ve focused on a new way of understanding diabesity as an autoimmune, inflammatory disorder, and we’ve looked in a general way at the underlying mechanisms (inflammation, genetics, environmental triggers and leaky gut) that contribute to diabesity.

Now that we’ve laid that foundation, we’re going to take a closer look at some of those mechanisms. In this article, we’ll discuss the three major dietary toxins that trigger diabesity:

  • Cereal grains (especially refined flour)
  • Omega-6 industrial seed oils (corn, cottonseed, safflower, soybean, etc.)
  • Fructose (especially high-fructose corn syrup)

At the simplest level, a toxin is something capable of causing disease or damaging tissue when it enters the body. When most people hear the word “toxin”, they think of chemicals like pesticides, heavy metals or other industrial pollutants. But even beneficial nutrients like water, which are necessary to sustain life, are toxic at high doses.

In the Perfect Health Diet, Paul & Shou-Ching Jaminet apply the economic principle of declining marginal benefits to toxins:

It implies that the first bit eaten of any toxin has low toxicity. Each additional bit is slightly more toxic than the bit before. At higher doses, the toxicity of each bit continues to increase, so that the toxin is increasingly poisonous.

This is important to understand as we discuss the role of each of the dietary toxins listed above in contributing to diabesity. Most of you won’t develop diabesity by eating a small amount of fructose, cereal grains and even industrial seed oils. But if you eat those nutrients (or rather anti-nutrients) in excessive quantities, your risk of diabesity rises significantly. This is especially true if you have any of the genes that predispose you to diabetes and obesity.

The primary effect toxins have on the body – whether dietary or otherwise – is inflammation. And since we now know that diabesity is an autoimmune, inflammatory disease, it’s clear that anything that causes inflammation is a potential risk factor for both diabetes and obesity.

The impact of each of these dietary toxins could fill a book. And in fact, there are several such books and many other blogs that have covered this material in detail. Rather than re-create the wheel, I’m going to provide a brief summary and then link you to resources if you want more detail.

Cereal grains: the unhealthiest “health food” on the planet?

The major cereal grains – wheat, corn, rice, barley, sorghum, oats, rye and millet – have become the staple crops of the modern human diet. They’ve also become the “poster children” of the low-fat, high-carbohydrate diet promoted by organizations like the American Heart Association (AHA) and American Diabetes Association (ADA). If you say the phrase “whole grains” to most people, the first word that probably comes to their mind is “healthy”.

But the fact is that most animals, including our closest relative (the chimpanzee) aren’t adapted to eating cereal grains and don’t eat them in large quantities. And humans have only been eating them for the past 10,000 years (a tiny blip of time on the scale of evolution). Why?

Because plants like cereal grains are always competing against predators (like us) for survival. Unlike animals, plants can’t run away from us when we decide to eat them. They had to evolve other mechanisms for protecting themselves. These include:

  • producing toxins that damage the lining of the gut;
  • producing toxins that bind essential minerals, making them unavailable to the body; and,
  • producing toxins that inhibit digestion and absorption of other essential nutrients, including protein.

One of these toxic compounds is the protein gluten, which is present in wheat and many of the other most commonly eaten cereal grains. In short, gluten damages the intestine and makes it leaky. As we saw in the last article, a leaky gut is one of the major predisposing factors for diabetes and obesity.

Celiac disease – a condition of severe gluten intolerance – has been well known for decades. These people have a dramatic and, in some cases, potentially fatal immune response to even the smallest amounts of gluten. However, what is less well known is that wheat gluten triggers an immune response and gut inflammation in almost everyone – regardless of whether they are “gluten intolerant” or not. Over 80% of the population develops measurable gut inflammation after eating wheat gluten.

Dr. Kurt Harris, author of one of my favorite blogs (PaleoNu), calls wheat one of the three “neolithic agents of disease” (we agree on the other two as well). For more information on the toxic effect of cereal grains, see Dr. Harris’s two articles “The argument against cereal grains” and “The argument against cereal grains, part II“.

Industrial seed oils: unnatural and unfit for human consumption

Industrial seed oils (corn, cottonseed, soybean, safflower, sunflower, etc.) have not been a part of the human diet up until relatively recently, when misguided groups like the AHA and the ADA started promoting them as “heart-healthy” alternatives to saturated fat.

The graph below shows how dramatically seed oil consumption has risen over the past several decades:

pufaconsumption

Industrial seed oils are extremely harmful when consumed in excess. I’ve written about this at length in my series on essential fatty acids. In the context of this article, researchers have shown that industrial seed oils have played a significant role in the current obesity epidemic.

A recent study showed that a diet with an omega-6:3 ratio of 28 (meaning 28 times more omega-6 than omega-3 fats) caused obesity that progressively increased over four generations of mice. This means that eating too much omega-6 didn’t only cause obesity in the current generation, but it also predisposed future generations eating the same diet to developing obesity.

This is bad news for those eating a Standard American Diet, which contains an omega-6:3 ratio that is very similar to what the mice in the study above were fed.

Omega-6 seed oils have also been shown to cause inflammation, insulin resistance and impaired leptin signaling, all of which directly contribute to diabetes.

Finally, industrial seed oils have been shown to interfere with thyroid function by blocking the binding of thyroid hormone to its receptors. The result is a higher fat mass and a less efficient metabolism.

For more information on how seed oils contribute to diabesity, see The Body Fat Setpoint, Part III: Dietary Causes of Obesity, Have Seed Oils Caused a Multi-Generational Obesity Epidemic?, and my series on Essential Fatty Acids.

Fructose: the sweetest way to get diabesity

White table sugar is composed of two sugars: glucose and fructose. Glucose is an important nutrient in our bodies and is healthy, as long as it’s consumed in moderation. Fructose is a different story.

Fructose is found primarily in fruits and vegetables, and sweeteners like sugar and high-fructose corn syrup (HFCS). A recent USDA report found that the average American eats 152 pounds of sugar each year, including almost 64 pounds of HFCS.

Unlike glucose, which is rapidly absorbed into the bloodstream and taken up by the cells, fructose is shunted directly to the liver where it is converted to fat. Excess fructose consumption causes a condition called non-alcoholic fatty liver disease (NAFLD), which is directly linked to both diabetes and obesity.

A 2009 study showed that shifting 25% of dietary calories from glucose to fructose caused a 4-fold increase in abdominal fat. Abdominal fat is an independent predictor of insulin sensitivity, impaired glucose tolerance, high blood pressure and high cholesterol and triglycerides.

In a widely popular talk on YouTube, Dr. Robert H. Lustig explains that fructose has all of the qualities of a poison. It causes damage, provides no benefit and is sent directly to the liver to be detoxified so that it doesn’t harm the body.

Another danger of fructose is that it reacts with polyunsaturated fats and proteins to form toxic compounds called Advanced Glycation End-Products (AGEs) in a process known as “fructation”. (Who comes up with these words?) AGEs wreak all kinds of havoc on the body; they damage DNA, speed up the aging process and cause high blood pressure and kidney disease. And studies have shown that fructose is up to 10 times more likely to produce AGEs than glucose.

For more on the toxic effects of fructose, see The Perfect Health Diet and Robert Lustig’s YouTube talk: Sugar, The Bitter Truth.

A toxin-free diet prevents and even reverses diabetes

In addition to all of the evidence above, we have two other lines of evidence that strongly indicate that cereal grains, seed oils and fructose contribute to diabesity.

First, diabesity is either non-existent or extremely rare in hunter-gatherer cultures that don’t consume these toxic foods.

Second, two studies have shown that a paleolithic diet (free of cereal grains, seed oils and excessive fructose) produced dramatic improvements in cardiovascular and metabolic markers.

The first study, performed by Dr. Staffan Lindeberg and colleagues, found that a paleolithic diet was superior to the mediterranean diet in several ways. These are summarized in Stephan Guyenet’s article on Lindeberg’s study:

  • Greater fat loss in the the midsection and a trend toward greater weight loss
  • Greater voluntary reduction in caloric intake (total intake paleo= 1,344 kcal; Med= 1,795)
  • A remarkable improvement in glucose tolerance that did not occur significantly in the Mediterranean group
  • A decrease in fasting glucose
  • An increase in insulin sensitivity (HOMA-IR)

The most remarkable outcome of the study is that, although 12 of 14 participants had elevated fasting blood sugar at the beginning of the trial, every single participant had normal fasting blood sugar at the end of the trial.

Dr. Lindeberg published a follow-up study in 2009. In this case they compared a paleolithic diet with a conventional ADA low-fat “diabetes diet”. While the results weren’t quite as impressive as the first one, they were still very encouraging. Participants in the paleolithic group:

  • Reduced HbA1c more than the diabetes diet (a measure of average blood glucose)
  • Reduced weight, BMI and waist circumference more than the diabetes diet
  • Lowered blood pressure more than the diabetes diet
  • Reduced triglycerides more than the diabetes diet
  • Increased HDL more than the diabetes diet

At the end of the trial, 8 out of 13 patents still had diabetic blood glucose levels. However, in this study the patients had well-established diabetes for an average of 9 years. Over time diabetes progresses to beta cell destruction, which reduces insulin output. Once this point has been reached, dietary changes can be helpful but cannot completely reverse diabetes.

What this means, of course, is that the earlier you remove these toxins from your diet, the better chance you have of preventing and even reversing diabesity. And while a paleolithic diet may not reverse diabetes in those that have had it for several years, it still produces significant improvements.

** A donut is the perfect diabesity food. It’s got refined flour (cereal grains), industrial seed oils (plus trans fats for an added bonus), and plenty of high-fructose corn syrup.

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Comments Join the Conversation

  1. Jes says

    Hi Chris,
    I would love to know what effect fruit has on the body, is it still considered dangerous in large amounts? I am asking because my sons love fruit and some days my eldest (4) will eat up to 6 pieces. Am i putting him in danger of non alcohol related fatty liver or type 2 diabetes, is all that fructose wreaking havoc on his little body?
    I would very much appreciate an answer as i am worried i could be harming him. Thankyou

  2. Dariusz says

    “Cereal grains: the unhealthiest “health food” on the planet?
    The major cereal grains – wheat, corn, rice, barley, sorghum, oats, rye and millet – have become the staple crops of the modern human diet.” Quackery if they are unhealthy so why Japan Taiwan Hong Kong Itally France are heathiest nations and Japan Taiwan Hong Kong also the highest IQ and in this countriest they eat? White rice (in japan also soy in miso soup daily) Italy pasta in france high bread.

  3. Carrie says

    I was recently diagnosed with gestational diabetes. I have always had a problem with sugar and grains, so have avoided them. I was shocked when all of the diabetes “experts” I was sent to literally spent hours trying to convince me that if I did not eat grains, breads, and pasta, I was starving my baby. They wanted me to eat 175 grams per day of these refined carbs and then give me insulin, although on my current diet, my blood sugars are well under control. They also tell me that any ketones they find in my blood are toxic for the baby. I have put my foot down, but I have never felt so pressured in my life! It has been a very stressful experience. ANyone else have experience with gestational diabetes and eating paleo? THX

  4. Kerry Potter says

    Hi Chris!~

    I love your articles. I am a holistic dietitian myself who specializes in diabetes. This may be a silly question but do you consider quinoa to be a cereal grain that would contribute to diabetes??

    Kindly,

    Kerry Potter

  5. Seeking says

    Chris,

    I love your blog and I find myself reading it often. However, you stated: “Over 80% of the population develops measurable gut inflammation after eating wheat gluten.” I don’t think it’s accurate to extrapolate that conclusion from a very tiny study of such a small group of people to the entire population. Also, the non-celiac people in this particular study had strong symptoms of gluten sensitivity, whereas most of the population does not experience any symptoms.

    I’m suspecting, however, that a large amount of the population probably does have an immune response to gluten, but your extrapolation from that very tiny study is not logically justified. Have there been any studies done since that one that involve larger groups of people? I’d be extremely interested to read them.

  6. Ryan says

    While I agree with much of the sentiment. I’m not really sure you understand evolutionary theory. Best to just stick to a ‘Hey, this is healthful!’ type of argument.

  7. Shawna says

    Dear Chris,

    I am hoping that you can help me. I have maintained a diet with no white flour or sugar for over 20 years, good oils and fats, fruit limited to occasional berries, and very limited carbs (from vegetables, legumes, and an occasional sweet potato). Although I was 10 pounds overweight and frustrated, I realized that there was something not working properly in my body when I gained 17 additional pounds in a calendar year. I was just diagnosed with insulin resistance and was put on Metformin as my only option to re-sensitize receptors with cream testosterone and DHEA as well. The medicine or testosterone or other imbalance has me really retaining water as well.

    I am willing to test any theories if you have not already researched this particular case. I would like to be able to help people with what we learn.

    I have just started seeing an acupuncturist who is fantastic. He has seen me twice and says that I am very healthy but he can tell how I am out of balance and believe under the layers, it may be hormonal.

    Gratitude and Blessings,

    Shawna

  8. says

    The fat issue is important and was a missing key for a long time.

    So many of us diabetics went low-carb in the 80s and 90s to control bg. Almost by definition, a low-carb diet is high fat, and we ate “healthy” fats – corn oil, soy oil, canola oil, margarine. Thus we found diabetes progressed in spite of low carbing.

    It probably progressed faster for those of us doing the bad fat thing than those who weren’t even TRYING to eat healthy.

    (The diabetics who followed the opposite advice, to eat low-fat diets, progressed even faster with their “whole grains”.)

    I have found my insulin needs decreased on a diet with protein primarily from pasture-raised meat, eggs and raw dairy (and to a lesser extent, nuts & seeds and their butters) and fat primarily from pasture-raised butter, coconut oil, olive oil and avocado oil. (I also supplement fish oil cause I don’t eat much fish).

    I theorize this not only is due to inflammation, but also because cell receptors are made out of lipids, and a diet with almost no saturated fat and heavy on the omega-6s makes for deformed cell receptors, and hence insulin resistance and thyroid resistance, etc. If I’m correct, I expect my insulin needs will continue to decrease for several years as my body rebuilds from the appropriate components.

    BTW, the season matters with butter. A local dairy makes butter with no ingredients but cream and salt, so the color varies. When the grass is growing fastest, the butter takes on a very rich dark yellow color. And I buy 40 lbs of that stuff for the freezer! Chockful of vitamins A, D3 and K2! Good stuff.

    Also, yummy fats make it easy to increase produce intake too. A giant salad topped with olive oil and red wine vinegar, multicolored bell peppers and onions stirfried in avocado oil finished with lime juice, meat and vegetables curried in coconut milk, broccoli with raw cheddar melted over it, avocados dipped in butter, berries floating in heavy cream… in this house, we’d never get through all the CSA veggies without good fats!

  9. Chris Kresser says

    Both groups improved, with the paleo group improving more. The question is always “where were these study participants coming from” in terms of diet. Usually the Standard American Diet is the answer. We don’t know if Lindeberg’s group would have improved even more by limiting fruit intake and emphasizing saturated fat (I suspect they would have).

    Ultimately, I don’t believe a moderate amount of fruit is a problem for people with healthy metabolisms, as I’ve stated in the comments. I do have patients that can’t tolerate even a piece of fruit without their blood sugar spiking over 140 mg/dL, which is the danger zone. So as usual, the answer to “is fruit okay” is “it depends”.

  10. Johnny Bourdeaux says

    In the Lindeberg’s paper fruits consumption was 493 ± 335 per day in the Paleolithic group and 252 ± 179 grams in the Consensus group.

    http://www.springerlink.com/content/h7628r66r0552222/fulltext.html

    Too short a duration, perhaps? If so, that would perhaps explain why in a consequent study on diabetics, averaging 8 years from diagnosis, the results were less flattering? Lindeberg further stresses the nada effect in his brand new book (2010).

    I’d love to hear your thoughts. I for one would not consider Lindeberg’s paleo version as the automatically best one out there.

  11. Johnny Bourdeaux says

    Hi Chris, I enjoyed your briefing here.

    However, I’ve seen you referenced Linedeberg’s paleo trials as a proof on healthiness of your recommendations. Lindeberg did not see any association whatsoever with fruit / or fructose take and health markers in his trials. What would you see as the reason of this ?

  12. says

    Thanks so much for that quick response! I really commend you for the research you’re doing into the subject and I agree with you about most things.

    I will just add that, yes, skinny people can get diabetes (especially alcoholics!), but I said lean people who exercise regularly don’t get diabetes (they are two different populations of people). I should have made that more clear.

    I am also glad that we agree that fruits and vegetables are not bad. The culprit is a mix of factors. I have spent time working as a physician in Guatemala and the diabetes rate in rural Gautemala is astounding. They have a diet which consists largely of carbohydrates and they are sedentary – and I believe also genetically predisposed to not being able to process the high % of carbs in their diet. It is a bad combination.

    Anyway, bottom line is avoiding diabetes can be achieved by regular exercise (think nomadic lifestyle), staying lean (not skinny) and eating a balanced diet (with fats and protiens, esp. fish). An orthorexic diet, which avoids all fructose is certainly not the answer, but I don’t think you’re suggesting that either.

  13. Chris Kresser says

    Thanks for your comment.

    I have to disagree that people who are lean and who exercise don’t get diabetes. Please see my previous article on that subject. I do agree that they are in the minority.

    I didn’t recommend that people stop eating fruits and vegetables. I said, and the scientific literature supports me in this, that fructose is fructose – no matter where it comes from. Fructose is handled by the body as a toxic substance. It is shunted directly to the liver for processing, like other toxins (and unlike glucose or any other macronutrient), and in excess amounts it causes a host of metabolic problems.

    It’s true that corn doesn’t “cause” pellagra, as you pointed out. I didn’t word that carefully. But eating too much corn at the expense of other nutrient-dense foods containing B3 does. It’s also possible that the fructose in corn disrupts vitamin and mineral metabolism in ways we don’t fully understand yet.

    The ADA dietary recommendations (a low-fat, high-carb diet) for diabetics (by definition, people with poor glucose control) remain one of the most asinine pieces of advice ever handed out. Eating a lot of fruits and vegetables is NOT what prevents diabetes. Avoiding refined flour and industrial seed oils, along with high quantities of fructose, does.

  14. says

    Alright – my husband just told me I had better add that I am an MD, PhD. Not that that really matters. But I do have a professional interest in the above topics and I’m not just writing to badger you.

  15. says

    Hi Chris,

    I just ran across your blog. Thanks for gathering all of the research. It was an interesting read. I certainly agree that too much fructose in the diet is not a good thing, especially high fructorse corn syrup. But I think it is going a bit far to discourage people from eating fruits and vegetables because they contain fructose. Fruits and vegetables do not cause diabetes. Eating too much and being sedentary causes diabetes. People who are lean and exercise (and eat fruits and vegetables – or candy for that matter) don’t get diabetes (there are a few exceptions, notably Type 1 diabetes).

    I also have to doubt that fructose in and of itself is a toxin. Perhaps it could be viewed this way in people who are already overweight and/or have metabolic syndrome – in which case extra fructose won’t help anything.

    Finally, I have trouble understanding how corn could CAUSE pellagra. Pellagra is vitamin B3 (niacin) deficiency and is caused by just that- lack of vitamin B3. One would basically have to eat only corn (and no B3) for a long period of time – this is what has been seen in some poor cultures subsisting on maize alone (where pellagra has been seen). But corn doesn’t cause the defficiency.

    Anyway, don’t take my comments too personally – I commend you for initiating an interesting debate.

  16. Chris Kresser says

    Good question, Charles. But it’s not the same rationale. From an evolutionary perspective, the availability of sweet fruit with high fructose content was limited to certain times of the year. Also, today’s fruit is likely much sweeter than what our ancestors ate because it has been bred for for that purpose over many generations.

    Like most compounds, fructose is well-tolerated by people with healthy metabolisms in small amounts. But, in larger amounts, or in people with metabolic derangement, fructose is definitely problematic.

  17. Charles says

    Hi Chris,

    I love your posts and am in the process of adjusting my diet based on your writings. This is the first time I’ve heard advice to limit your fresh fruit intake (aside from the seemingly unhealthy tenets of diets like Atkins, etc.).

    I’m a bit confused though on your evolutionary argument about cereals protecting themselves with toxins from consumption by the likes of humans. This makes sense to me. But are you also saying that fruits contain toxins (fructose) to discourage us from eating them? Aren’t fruits sweet precisely to encourage us to eat them and spread their seeds? What would be the point of poisoning the vehicles on which they rely to propagate?

    Perhaps I’m confusing two different ideas but was just wondering if you have an explanation that can clear up my need to understand the logic of this.

  18. Chris Kresser says

    Jae: yes, that was a small study and we’ll need more research to confirm the 80% figure. However, the mechanism is plausible and well-known, and as you’re aware there are several other lines of evidence implicating gluten’s immune dysregulating properties. That’s enough to convince me it’s best avoided.

  19. Jae says

    I’m a bit late to the party (catching up on reading). Thanks for the excellent article, as always.

    Can you address the 80% figure that you provide for gut inflammation via gluten consumption? It looks like the sample size of that study may have been as small as 6.

    Mind you, I avoid all grains except for occasional white rice, and I’m fully on board with the idea that gluten is the most problematic of all the grains. I just want to verify if I’m reading the study correctly. I remember seeing Peter from Hyperlipid post on this a while back, but never asked him about it.

    Thanks!

  20. Jesse says

    I mean, for example, if you have a sucrose-sweetened soft drink, which will have more sugar in total but less fructose compared to glucose, vs. a HFCS-sweetened drink, which has less sugar but more fructose compared to glucose, is there a reason to choose one over the other?

  21. Jesse says

    Ok thanks, that makes sense. Does it make a difference, though, that fructose is sweeter than glucose or sucrose, so you wouldn’t need to use as much of a mixture with more fructose monomer?

  22. Jesse says

    Hey Chris,
     
    What is it about HFCS that is so bad that you would single it out, compared to other sweeteners (sucrose, honey, maple syrup, agave nectar, fruit juices)?

    • Chris Kresser says

      Fructose is worse than glucose (by far), so any sweetener that has more fructose than glucose is more detrimental. HFCS is 55% fructose and about 42% glucose, whereas sucrose is 50/50. Agave nectar is even worse. It’s fructose content ranges from 56% to 92% depending upon the source. Honey is 38% fructose. A healthy person with normal glucose tolerance can handle small amounts of this stuff, but in larger amounts or in people with deranged metabolisms they will wreak havoc.

  23. says

    Thanks Chris
    I’ve had a busy summer and fall, transitioning into early retirement. Closing and selling various businesses, etc. I’ll have more time to blog soon, hopefully. I quite liked your thyroid series, too. Keep up the good work.
    Kurt

  24. says

    Great post and great blog. Thanks for the hat tip. I first referred to wheat, fructose and linoleic acid as the “neolithic agents of disease” in an email exchange with Stephan Guyenet over a year ago. Thanks for helping spread the meme and I’d be happy to see that terminology propagated.
    I think wheat explains the existence of atherosclerosis in egyptian mummies, wheat and sugar explain the diseases of civilization introduced to aboriginal populations by the white man, and 20th century industrial seed oils added to the former the western epidemic of heart attacks and – to use your term – “diabesity”.

    • Chris Kresser says

      Hi Dr. Harris,

      Thanks for stopping by. I’m a big fan of your blog (I miss your articles, in fact!) I also liked your “three horsemen” term. I’ll add a reference to neolithic agents of disease to the text, right before the links to your articles.

  25. Jesse says

    Actually, now that I think about it more…
    “Unlike animals, plants can’t run away from us when we decide to eat them. They had to evolve other mechanisms for protecting themselves.”
     
    By that argument, what vegetables SHOULD be healthy? Rice, carrots, spinach, broccoli, onions, potatoes, beans, celery… they should all have toxins. Almost all that’s left is fruit, except that’s no good either because it has fructose. So all that’s left is meat and other animal products. You’d think that it’d be impossible to find a healthy vegan.
     
    What the three things you listed have in common is that people in America eat too much of them. Eating too much of anything will make you sick. Why not simply advocate moderation?
     
    Though incidentally, I agree with you about seed oils.

  26. Jesse says

    Okay, thanks. The articles you linked do seem to make more sense than what you said here, or at least Part I does.

  27. says

    Great Article (as usual). It’s so funny you used a donut. My son was almost three when we put him on the SCD for autism. An ELISA IgG Food panel showed multiple food issues, which was actually good because we needed proof for the state. His daycare was a state certified one. We had to have a reason why he was bringing his lunch and not eating the state approved lunch. The next year he went to PPCD (special ed preschool through the local school system). The public school lunch cafeteria each week served glazed doughnuts and bearclaws to the children for breakfast. So for me, the donut symbolizes alot that’s gone wrong with our health.

    I really enjoy all your health series posts, keep it up.

  28. kb says

    I guess the way you phrased the sources of fructose without clarifying that fruit—in it’s entire package—contains fiber to slow down the fructose absorption would make the average person afraid to eat fruit.  I just visited a whole host of websites offering natural treatments for fatty liver disease that recommend eating plenty of WHOLE RAW FRESH FRUITS AND VEGETABLES.  I think if you have someone with an already compromised system suffering from diabetes, obesity or fatty liver whose body needs intensive healing if not already too late, limiting overeating of ANY food product—even including lots of sweet fruits—would be important. But I don’t agree with giving this blanket (fruit has fructose, so is bad) advice to someone who already is in great health—because someone who is already healthy and eating very well with fruits, veggies and meats would be very unlikely to get obese, diabetic or fatty liver even from eating a pound of bananas a day.  What exactly is considered excessive fruit intake anyways?  I guess you would have to compare glycemic index’s of Twinkies, sodas etc. and other easily excessively consumed sugary foods with the glycemic index of whole, raw fruits—taking into consideration the built in fructose absorption altering fiber in the fruit to make the determination of just ‘how’ much fruit is ‘bad’ for a human.  My assumption would be pounds and pounds of fruit a day—which most people don’t and couldn’t tolerate anyways.

    • says

      Fructose has nothing to do with the glycemic index. Most carbohydrates break down or convert to glucose and thus have an effect on blood glucose. Fructose is unique in that it is a 5-ring sugar that cannot be converted to glucose (which is a 6-ring sugar).

      Fructose is removed from your bloodstream by the liver, which processes it by converting it to triglycerides. The triglycerides are then released back into your bloodstream. This is what fructose DOES; it’s basic biochemistry.

      Now your body has a process called gluceogenesis that can convert protein and fat to glucose if you need it. So the specific atoms that made up fructose could eventually become glucose. But not directly, fructose is directly converted to fat.

      Whether it’s bad or not depends. If you are a hunter/gatherer trying to put on weight to make it through a lean winter, then it’s good. If you have a family history of heart disease and/or diabetes and eat too much of it, then it’s bad.

      And btw, bananas are also full of glucose… too much for me, as a diabetic, to eat as they spike bg badly. If you really, really have to eat a pound of fruit a day, I’d recommend berries instead.

  29. Chris Kresser says

    I did not say that fruit is more harmful than packaged food or grains.  Nor did I say that fruit is responsible for the epidemic of fatty liver disease.  Clearly HFCS is the primary culprit.  But that doesn’t mean that people can eat unlimited amounts of fruit without adverse effects. If you understand how fructose is processed, this should be clear.

  30. Chris Kresser says

    Fructose is fructose.  It is processed in the same way, regardless of where it comes from. That’s a fact, and it’s not controversial.

    If we were meant to consume fructose in large amounts, then the body wouldn’t treat it as a toxin (i.e. shunt directly to the liver and store as fat to remove it from circulation). Glucose is an entirely different story, since it’s rapidly absorbed into the bloodstream and is a critical ingredient in energy production (ATP).  We can live without fructose, but we can’t live without glucose.

    Once again, I am not saying fruit is “bad”.  As I said in the article, anything can be toxic at high doses – including water.  Our ancestors didn’t have the kind of access to fruit that we have today.  It was largely seasonal, and they weren’t growing it themselves on huge plots of land.  The fructose content of paleolithic fruit was also much lower than the varieties we have today (which have been selected for sweetness over many generations).

  31. kb says

    I have also sent an inquiry to Dr. Doug Graham of FoodnSport and the Fruitarian 80/10/10 diet and let him know your take on how harmful fruit is.  Simply because I just find it impossible to believe that eating fruit, along with lots of veggies and good meats could cause one to be the unhealthy, fat pigs that many Americans are—with fatty liver and all.  I just find it unbelievable that you could even give this advice.  Fruit will ALWAYS be better than ANY packaged crap, baked crap or grain.

  32. kb says

    I still don’t buy that fruit, in it’s natural state is as bad as you and others are saying.  Please link me studies and information to prove this.  I would bet that fruit ALONE could not cause the fatty liver etc.  There simply HAVE to be other factors contributing.

  33. says

    Chris: I believe the same thing about why the average lifespan used to be shorter (“accidents, infant mortality and violent death”) but was wondering if you have any resources to back that up? I have friends who believe there was just as much cancer, diabetes, heart disease, etc. in the past. They believe that 1) people didn’t live long enough to develop some of the diseases (i.e. they believe these are age related diseases), and 2) they believe the medical community in the past didn’t have a way to diagnose these conditions. How can I prove them wrong?

  34. Chris Kresser says

    Jesse: read the two links at the end of the cereal grains section.  They will answer your questions.

    It’s not a question of survival.  It’s a question of optimal health.  And yes, our paleolithic ancestors didn’t suffer from the chronic, modern diseases that plague us today.  Their average lifespan was shorter because of accidents, infant mortality and violent death, but their overall health was superior.

  35. Chris Kresser says

    Bryan,
    I agree that white rice isn’t problematic for most people, and I eat it myself in small quantities.  Corn I’m less certain of.  It’s a common allergen, and it can cause pellagra in large quantities.  Nevertheless, I do believe that gluten is the main culprit.

  36. Jesse says

    So you’re saying that, because cereal grains were so unhealthy, our ancestors before 10,000 years ago didn’t eat them. Why did they start eating them at all then, and how did they survive all this time eating such poisonous food?

  37. says

    Another great post Chris!  My guess would be that when it comes to cereal grains, it’s primarily the glutenous grains that are most suspect in contributing to diabecity.  It’s the gluten that causes gut damage and inflammation. I’m not so sure rice is much to blame and maize may also be less of a problem.  I have read that rice bran may cause digestive problems, but white rice does not.  Also, I’ve read that long sourdough fermentation of a day or more may break down gluten so that it is less likely to cause problems.  Likewise, proper preparation of maize by nixtamalization makes it more nutritious and digestible.  Of course, I realize that most modern cereal foods are not prepared properly, with the possible exception of white rice.  Just some food for thought :)

  38. kevin says

    some fruit i wouldnt consider natural in my opinion….. But i really depends how you want to define natural….Banannas as we know them have only been around for 200 years or so.  They are a mutant that came out of a plantation of red and green cooking banannas.  Not that they are 100% bad…but i have seen some “fruitarians” eat banannas to the point where they got gout.   Everything in moderation..  I think people just eat too much in general….on top of that they eat crap….so the process is sped up.  Paleo all the way.  You would never find fruit often in natural.  Green veges mostly and an occasional animal if you are lucky.  Or you would be herding and foraging.  I met a masai warrior this past weekend.  He ate nothing but blood and milk till the age of 15 and looks better than some fruitarians i have seen.   The point is to eat natural diet and stay active.  35 bananas in one sitting is just digusting.  That is gluttony. Doesnt matter if its a 2 litter bottle of coke or 35 bananans its still too damn much for the body to handle.

  39. java says

    I would definitely like to respond to this one above. I believe that ultimately it all depends on your genes and other markers. I have not eaten any grain for the past few years. PUFA consumption is limited to occassional meals eaten in restaurants or elsewhere and sugar is something I dont touch,except for exactly one piece of chocolate once a week. Up until a few months ago [to be precise, till I saw Dr. Robert Lustig video] I ate plenty of fruit. Definitely two a day.I ended up with a fatty liver. Ever since I have given up eating as much fruit [I eat one fruit serving a week now], my fatty liver has cleared up.So I beg to differ and dont believe anyone who says fruit is safe just because it is natural. In the end,everything is natural…..grains are natural too,and ultimately all drugs are also natural.I agree with Chris that whichever way you look at it ,it is the same molecule. Remember the downfall of Adam was afterall the apple in the Garde of Eden.

  40. Chris Kresser says

    I didn’t say fruit is the same as HFCS.  I said fructose is fructose.  It’s the same molecule. And fructose gets processed by the liver in the same way, whether it comes from HFCS or fruit.  Of course HFCS is a toxic, highly refined and processed product, and fruit is natural. But that doesn’t mean we can eat as much as we want of it and function optimally.  Humans did not have the kind of access we have to fruit now – especially the sweeter fruits – until relatively recently on the scale of evolution.  We are not adapted to eat unlimited amounts of it – the way the liver processes fructose is proof of that.  I’ve worked with several people that on a strict paleo diet, and still have symptoms because they’re eating too much fruit.  When they reduce the fruit, the symptoms (and their blood sugar) abate.  So while I agree that eliminating grains is ultimately more important than moderating fruit intake, I certainly don’t agree that eating pounds of fruit a day is advisable for anyone.

    • Lynne P says

      What constitutes a serving of fruit? Is it one apple or half of an apple? If I should only have 2 servings per day, it makes a difference. I had one cup of blueberries for breakfast. Is that a serving?

      One other question. Fructose is processed by the liver. Does eating anything else with the fruit make any difference in the way fructose is processed?

      Thanks for your blog. As someone recently diagnosed with diabetes, I have a great interest in learning all I can about it and about the pale style of eating.

  41. kb says

    How can you compare the fructose in HFCS to that in fruit—-and suggest that fruit could possibly be as toxic as HFCS?!  I am appalled at this.  Have you even seen the incredible health of Fruitarians?  Their body habitus certainly doesn’t support your suggestions that the fructose in fruit is even remotely as dangerous as the chemically engineered product called HFCS.  There is a HUGE difference because the sugar in fruit is just a PART of the entire package—which is why eating fruits and vegetables over grains and other crap is so much better for a body.  Take away grains 100% and ONLY eat fruits, veggies and meats and you can pretty much cure the human body of all diabesity—even eating pounds of fruit a day!

  42. Ann says

    Chris, Your answer on the 5% more fructose in HFCS question seems too important to hide in the comments–especially with the current ad campaign to shift the label to “corn sugar.” In addition, there are the issues of trace amounts of mercury from processing corn into HFCS and the consumption of GMO corn via this pathway. A new post that investigates the specific harm of HFCS (versus fructose in general) might be helpful for folks who are feeling persuaded that HFCS is no different from sugar.

  43. Chris Kresser says

    Of course they’re both best avoided.  But the threshold for fructose toxicity is so low, that it make sense to do everything we can to avoid excess amounts.  5% may not be a large difference, but in the context of 150 pounds a year of sugar (the average American’s intake), it’s not insignificant.

  44. woly says

    I think it was Eades who said that he wasnt too concerned about HFCS specifically (as opposed to sugar in general) since it is only 5% more fructose than glucose. What is your opinion on this?

  45. Chris Kresser says

    Fructose is fructose, and is processed in the same way whether from HFCS or fruit.  So yes, I do recommend limiting fruit intake to about 2 servings per day as a general rule.

    • Chris says

      So how do you explain Dr. Robert Morse’s success with countless chronic disease cases including cancer with a diet basically consisting of fruit?

      I think there are many wise tales, half truths, and speculation in medicine. There are many people who practice a particular ideology based on what hey have heard from people before them. Well, this guy is actually doing it and finding out that the results are not what people claim will happen.

      This isn’t to say that I believe in fruitarianism, but I do think there may be something to be said for his success. I don’t care to hear about theory, I care about seeing something at work first hand and getting my knowledge this way.

  46. TimL says

    Chris,
     
    Regarding the toxicity of fructose, are you recommending any specific limit on fruit intake? Or is it primarily HFCS and refined sugar we have to worry about?

    • says

      The difference between HFCS and fruit is HUGE. Fruit is full of fiber and many micronutrients, vitamins, flavanoids, etc.

      You’re not going to get too much fructose from *whole* fruit unless you binge on the stuff.

      The thing to avoid besides HFCS itself is juice. Juice concentrates the sugars down. An orange only contains 2 oz of juice! So a 16 oz serving of OJ is equivalent to 8 oranges! It’s darned easy to drink a 16 oz glass of juice, but pretty rare that anyone would sit down and eat 8 oranges.

      Also, some fruits are relatively low-sugar. Berries are good, and have lots of micronutrients – going through a quart in a week is fine. Small servings of melon (like a cup of melon balls).

      A pomegranate similarly has lots of good micronutrients. I consider half an apple or pear a “serving”. And I’m NEVER giving up peaches when the local ones are in season, too yummy. ;)

      If you avoid HFCS and juice and just stick to whole fruit, it’s hard to overdo assuming you’re also eating meat, dairy and vegetables.

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