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Were We Wrong About Fiber?

In my video Is the Fiber Theory Wrong?, I present that fiber-containing foods may not only help prevent heart disease, but also help treat it as well. Heart patients who increase their intake of fiber after their first heart attack reduce their risk of a second and live longer than those who don’t. But what if we don’t want to have a heart attack in the first place? If 7 grams of fiber gets us a 9 percent reduced risk, would 77 grams a day drop our risk by 99 percent? That’s about how much fiber they used to eat in Uganda, a country in which coronary heart disease, our number-one killer, was almost nonexistent.

Heart disease was so rare among those eating traditional plant-based diets in Uganda that papers were published with such titles as “A Case of Coronary Heart Disease in an African.” After 26 years of medical practice in East Africa, doctors finally recorded their first case of coronary heart disease (in a judge who consumed a “partially Westernized diet,” in which fiber-free foods, such as meat, dairy, and eggs, displaced some of the plant foods in the traditional diet).

Were there so few cases because Africans just didn’t live very long? No, the overall life expectancy was low because of diseases of childhood, such as infections, but, when Africans reached middle age, they had the best survival rates, thanks in part to our number-one killer being virtually absent. Of course, since diets have been Westernized across the continent, coronary heart disease is now their number-one killer as well, going from virtually nonexistent to an epidemic.

Some blame this change on too much animal fat, while others blame it on too little fiber, but they both point to the same solution: a diet centered on unrefined plant foods. In fact, sometimes, it’s easier to convince patients to improve their diets by eating more of the good foods to crowd out some of the less healthful options.

The “dietary fiber hypothesis,” first proposed in the 1970s, zeroed in on fiber as the dietary component that was so protective against chronic disease. Since then, evidence has certainly accumulated that those who eat lots of fiber appear to be protected from several chronic conditions. But maybe fiber is just a marker for the consumption of foods as grown, whole, unprocessed plant foods, the only major source of fiber. Maybe all these studies showing fiber is good are just showing that eating lots of unrefined plant foods is good. “Fiber is but one component of plant food, and to neglect the other components [such as all the phytonutrients] is to seriously limit our understanding.”

Why did Drs. Burkitt, Trowell, Painter, and Walker—the fathers of the fiber theory—place all their bets on fiber? One possible explanation is that they were doctors, and we doctors like to think in terms of magic bullets. That’s how we’re trained: there’s one pill, one operation. They were clinicians, not nutritionists, and so they developed a reductionist approach. The problem with that approach is that if we reach the wrong conclusion, we may come up with the wrong solution. Burkitt saw disease rates skyrocket after populations went from eating whole plant foods to refined plant and animal foods. But instead of telling people we should go back to eating whole plant foods, he was so convinced fiber was the magic component that his top recommendation was to eat whole grain bread—though they never used to eat any kind of bread in Uganda—and sprinkle some spoonfuls of wheat bran on your food.

However, studies to this day associating high fiber intake with lower risk of disease and death relate only to fiber from food intake rather than from fiber isolates or extracts. It is not at all clear whether fiber consumed as a supplement is beneficial. In retrospect, it might have been a mistake “to isolate fiber from the overall field of plant food nutrition.” The evidence supporting the value of fruits, vegetables, and whole grains, as opposed to only fiber, has proved to be much more consistent. Whole plant foods are of fundamental importance in our diet. Fiber is just one of the beneficial components of fruits, vegetables, nuts, grains, and beans. “Much of the effort on defining fiber and studying the fiber isolate would have been better applied to a whole-plant-food approach.”

What would have happened if Burkitt and others had emphasized instead the value of plant foods? The value of eating unrefined plant food, which incorporates fiber and phytonutrients, might have been the focus of attention rather than just isolated fiber, which led to people shopping for their fiber in the supplement aisle instead of the produce aisle.

My Solving a Colon Cancer Mystery video is a perfect example of the concept I presented here. If fiber were really the key, then sub-Saharan Africa would be rife with colorectal cancer these days.

For an extreme example, how about disease reversal with a diet centered on white rice? See Kempner Rice Diet: Whipping Us into Shape and Drugs and the Demise of the Rice Diet.

My video The 5-to-1 Fiber Rule discusses a way to identify less processed foods using fiber as a marker of whole foods.

For more intrigue in the world of fiber, check out Does Fiber Really Prevent Diverticulosis?.

And, if you’re thinking, “Dr. Who?,” then, for a historical perspective, see Dr. Burkitt’s F-Word Diet.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

42 responses to “Were We Wrong About Fiber?

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  1. If I am thinking Dr. Who, then, I am thinking Tom Baker, maybe David Tennant?

    I have been pondering the helping people to simply add in healthier food.

    That is what I have been working on.

    I have a few people eating steel cut oatmeal, Ezekiel bread and salad.

    And I gave them Dr. Fuhrman’s math, where once you hit 10% of your calories from meat, you start having Cancer grow. He said that at 5% animal products, he couldn’t differentiate in terms of Cancer. I know the heart attack studies is where going all the way WFPB is where the benefit is much higher, but it will be easier for them to get there after they get down to 10%.

    The ones who don’t mind eating fruits and vegetables, aren’t intimidated by adding in a salad and they are happy that they get to have bread again.

    I am hoping that I am understanding things well enough to genuinely help people, but even looking at the logic of Bredesen versus Barnard, it is still like trying to negotiate an obstacle course.

    1. Dr Bredersen is a respected researcher and academic.

      However he makes some extraordinary claims based on fairly weak evidence. I think the study used to demonstrate the effectiveness of his approach looked at just 10 people, for example. They say that extraordinary claims require extraordinary evidence. We do not see extraordinary evidence here.

      His approach was trademarked and promoted commercially as the MEND protocol. Here is a cautious review of it

      However, I understand that Dr Bredersen has since separated from that company and set up his own company. He now markets the approach as the Bredersen Protocol. His book no doubt helps sales.

      The statement that cholesterol should not be allowed to get under 150 is also a big red flag. Declining cholesterol is a symptom of Alzheimer’s – as it is of certain cancers for that matter. However advising that cholesterol should never be allowed to get under 150 to prevent Alzheimer’s is like saying that you should never lose weight if you want to prevent cancer. Both declining cholesterol and weight loss are recognised symptoms of Alzheimer’s and certain cancers. Yet we know that obesity is a risk factor for cancer and high cholesterol is a risk factor for Alzheimer’s. Both declining cholesterol and weight loss are symptoms of chronic disease not causes.

      That said, these sorts of statements appeal to people who don’t want to make the drastic lifestyle changes necessary to achieve healthy weight loss and to lower cholesterol. Consequently, they sell a lot of books.

      The alternative health crowd very sensibly say “follow the money” when talking about conventional medical and health care. Strangely (to my mind at least), they always refuse to discuss possible financial conflicts of interest when it come to the extraordinary claims of cures made by people selling particular therapies or therapeutic approaches.

      Caveat emptor.

    1. I’ve never had anyone benefit from just adding Metamucil to their diet.
      Some people with gut issues do benefit from Acacia fiber.
      But most people just need to eat fruit and vegetables. I recommend about 10-12 servings a day, varying colors and types, preferably organic.
      Of course beans have a lot of both protein and fiber.
      That sounds like a lot, but you just slowly add an extra serving every week or so to give your gut bacteria time to change. That allows you to get used to the fiber.
      Plus, as Dr. Gregor states, that tends to crowd out the bad stuff.

      1. Yes, me. You have to drink 16 oz. water with Metamucil and when you are over 80 too much water cause dilutes your blood sodium, causing serious problems.

  2. I will digress here and comment on the blog fruit stand picture: I bet the pic was taken in Brazil: baskets of sugar apples, jaboticabas and cashew fruit front and center. Thank you! It took me back to my childhood shopping with mom in the open street markets.

    1. I thought the picture was taken in Taiwan or some southeast Asian country because it reminded me of my childhood in Taiwan at the open market. I clicked in and saw the next picture next to it is shot in Vietnam. :-)

  3. Can anyone name all the lovely produce items in the photo? From L to R, top row first, I have:
    Oranges, avocados maybe in dark shadow, Bananas, Corn, Yucca/Cassava,
    Okra, Apple Bananas, Pears, pomelo?, Strawberries
    Grapes, -?-, plums or olives?, Persimon
    -?-(citrus), sapote?, Red Mango, Green Ataulfo Mango
    Also curious where this lovely market was. Costa Rica? Guesses?

    1. The exotic fruit I recognize from Brazil are: to the right of the green grapes are sugar apples, jaboticabas and cashew fruit. Above the cashew fruit are atemoyas and below the cashew fruit basket are pigmy papayas followed by mangoes on the left.

  4. Western thought has instilled within people a absolutists type of mindset.
    The idea of heaven or hell good or bad absolute considerations are in us regardless of our feelings on theology or philosophy. It is how we are taught to think regardless of specific category of thought such as theology.

    So in things such as these diet we look for singular agents of good in this specific fiber to remedy all that ails us.
    As we see with peoples taking vitamins and this and that for health. This one good substance will cure all illnesses. This diet plan or that. This exercise or that, and on and on.

    So of course he being a person of this unconscious absolutists mindset would find for fiber not for a whole of dietary inclusion all plant foods as being cause.
    Such is our tendency by cultural bias,,,we all tend to think this way and look for solutions in this manner of consideration of absolutes, goods and bads. But things rarely exist in this fashion…it is almost always a whole thing of food or diet or this or that. Isolation and isolated effect is rarely ever found.

    But we look for it and apply such to it when it does not. So fiber remedies this… can we think otherwise…..we are taught this thinking of solving things in this manner by application of absolutes. A good must remedy a bad. It is not that a good may be bad depending on degree or qualification.

    1. To add our studies then can be structurally set up to reflect this unconscious bias and as well the results may be interpreted(as this shows) in ways which reflect a absolutists bias.

      Not to say the western mindset is deficient or detrimental in many other fashions. A Asian mindset may inherit bias in a opposite direction to presume things connected and one when they are perhaps not.
      Which would have similar negative outcome in structural setup and interpretation of scientific result.

      Seems in both venues the application would have to be in light of the nature of the mindsets or in relation to them….that which produce them to find applicable true findings.

      1. Ron, that is an astute observation.

        You have a grasp on how different cultures process information. I see that you enjoy it.

        Coming from a Christian perspective, we have talked about things like that, in regards to faith. Half the Bible is a Greek mindset and half the Bible is the Torah. Even how the Jewish culture processes time and the calendar versus the Greek is so different. The Hebrew the letters even have a symbolism, the Greek every single letter has a numerical value.

        In Bible Study, we talk about things like Heptadic structure in the Greek, where the numerology of 7 is so deeply embedded that a mathematician said that it would have taken a hundred million super computers a million years to have written the genealogy of Matthew and kept the mathematical structure, because if one number was removed, that whole mathematical structure would have been destroyed and the Torah has symbolic codes, which is just as sophisticated, if not more.

        I wasn’t always a Christian. My family was secular. I think Sir Isaac Newton might be the one who got me interested. Maybe Ivan Panin, who challenged the newspaper The Sun to examine the math of the book.

        Anyway, I hate what man has done with the Bible very much, but I genuinely find the structure of the Book awe-inspiring.

        I am laughing, because I am not going to go into a “God’s Not Dead” type of challenge with the scientists. I hated that movie very much. It smacked of Christian looking down on everyone else, which is opposite of my understanding of the spiritual. I appreciated that Christians don’t want to be bullied either, but we have been the bullies often enough that sometimes it helps to be on the other side to build compassion and understanding.

        1. I have looked at topics like DNA and sacred geometry and I get the same sense of awe.

          I never knew how beautiful math and science could be.

          I hated both when I was young, but they have stolen my heart in these years.

  5. Dr. Gregor,

    First of all let me thank you for changing my life. I’ve gone from 252 lbs. to 181 lbs.; from a 46 pushing 48 waist down to a comfortable 32. I’ve now become a vegan and have done more reading and studying on the foods we eat. Even about not eating tomatoes due to lectins, etc. etc.

    My question for you is what about an occasional fast? Either a 24 hr. fast with one meal; or a 24 hr; 48 hr. or more without anything to eat other than water or black coffee. What about putting the body into a ketosis state that will pull fat from our fat storage and will keep us sustained without hunger. There is an enzyme/hormone that regulates hunger; guerlin I think, that after the initial shock to the body of no food is coming, that starts to decrease and we don’t feel hunger at all. When eventually we do feel the hunger then it’s time to eat. Just interested in your opinion on all of this.

    Thanks again for all that you do for so many. And who would have thought that the wiskbroom of the colon, broccoli, would become a favorite of mine. Try some hash browns on a plate covered with a vege burger. So good.


    Sheldon Goldner

    1. Mr. Goldner,

      I have been fasting, in the manner mentioned–water and black coffee only–for one day a week (usually Mondays), for over 32 of my 70 years. While it hasn’t performed miracles, I can testify that if I had to take a test, give a speech or meet a potential employer, I would always fast that day, i.e., from going to sleep the night before until awaking the next day. My mind and faculties of speech and thought are always much more alert on those days than any other.

      My simplistic belief is that by allowing the digestive tract to take the day off, the blood that usually works that part of the body is used elsewhere, to good purpose. I don’t know if it’s effective for any great weight loss or control, but it’s a practice that I find healthy and intellectually stimulating. Good luck if you decide to give it a try. One day per week ain’t all that much.

      1. Thea,

        Thank you so much for your reply. Is your fast with one meal or without any food for 24 hours? Have you ever extended the fast to several days? Just curious. I find that as long as I have my blender the vegan path is the easiest program to incorporate as a life style.

        1. Sheldon,

          I have done many fasts with the Christian community and you are right that you don’t tend to get hungry.

          I have done “Daniel Fasts” and “Esther Fasts” and other types of fasts as part of a spiritual setting of prayer.

          Generally, after the first few days, the hunger does shut off.

          I have never done a fast for a purely physical reason, but I have read about researchers doing it in the Diabetes community.

          Dr. Bredesen has people do a 12-hour fast between dinner and breakfast as part of his Alzheimer’s protocol.

          I am working toward that, but I haven’t read his book yet to see the rationale.

          Are you avoiding lectins?

          All of the WFPB doctors I have listened to and John Robbins have said that Dr. Gundry of The Plant Paradox is wrong and that he is keeping people away from the nutrition in those foods, and then, is selling supplements having people spend thousands and thousands of dollars on his products, instead of eating the nutrition.

          Dr. Greger has a few videos on lectins and has done interviews on night shades. With lectins, he says to cook your dried beans. For night shades, he says that 1 out of 20 people might need to avoid them for things like joint problems, but everybody else will get so much benefit from them that the advice to the 19 out of 20 people would be to eat them often.

          1. I forgot.

            I did have a Pastor end up in the ER after a week on a fast.

            I passed out and banged my head on the concrete the last time I did a water fast for the weekend and I probably won’t be doing it again.

            1. Steve Gundry is talking people into joining a VIP club and spending $10,000 a year on supplements and if you have been a fan of Dr. Greger’s videos, you will know that he has done several videos on how supplements often either don’t work the way the food works or they actually kill people faster.

              Even supplements like Green tea. The drink has nearly miraculous properties to heal you. The supplement increases your likelihood of getting cancer.

      2. “I can testify that if I had to take a test, give a speech or meet a potential employer, I would always fast that day,”

        It would be just my luck for my stomach to grumble…loudly….at the most inopportune moments. Nothing you need to worry about? :-)

    2. Sheldon Goldner,

      You’ll find the most comprehensive and trustworthy information on fasting at That is the website for TrueNorth Health Center in Santa Rosa, CA. They have over 30 years of experience with medically supervised fasting, both long and short, juice cleanses, and whole food plant based nutrition. Dr Goldhamer explains it all, as does Dr Klaper.

      Fasting more than for just a few days on water only should be supervised by an experienced medical team, who know what to do when things need tweaking in one way or another. They will be doing blood work (or looking at recent blood work you take with you), and checking for any signs of difficulty, and they will recognize when it is time to start breaking the fast.

      Fasting has been used to cure or reverse many disease conditions, especially intractable high blood pressure, diabetes, some cancers, interstitial cystitis, rheumatoid arthritis and other autoimmune conditions, heart disease, etc. Some have fasted as long as 42 days, and when body conditions show the doctor it’s time to end the fast, you should be guided into a safe program of refeeding and making dietary changes that will allow you to continue healing and stay well.

    3. Hi Sheldon- Thanks for your comments and WAY TO GO on your life change and dramatic health improvement. There is indeed evidence that fasting can have acute health benefits, namely decreasing inflammatory markers. Dr G has a nice video on the similar effects of fasting intermittently and long term following a whole food, plant based dietary pattern. Here’s a link to a video that may answer your question:

      Best to you! Dr Anderson, Health Support Volunteer

  6. Can the NF team consider a video on “fully hydrogenated fats?” After many years, we’ve finally banned partially hydrogenated fats, and the response by food manufacturers is “fully hydrogenated fats.”

    Yes I know to avoid processed foods. In an effort to educate the public, did they just replace a fraken food with the bride of franken food?

    BTW, PLEASE BRING BACK DISQUS! I hate this format and I won’t participate. Email discussions, how 20th century, not for me thanks.

  7. I have been watching a dietician talking about Bredesen’s Protocol and she started talking about Gluten and she said that the reason they don’t have Alzheimer’s patients eat it is that someone named DeSano did research and the peptides in gluten can’t be digested by anyone and that there is gliadin, which can cause transient openings in the epithelial layer and that the immune system can initiate low grade inflammation. She said that the gut epithelial layer is linked to the Blood Brain Barrier.

    I am putting this here, and am gonna try to go off gluten again. I had been off of it for most of last year, but went back on it in the form of things like Ezekiel bread.

    Is oatmeal gluten free? I will be bummed if it is.

    I also looked at the Ornish plan, which came with the Food Revolution Summit extras and couldn’t handle that 1 walnut is a serving size. I like Dr. Greger’s handful of nuts better.

    Dr. Bredesen has people eating 15 servings of non starchy vegetables, if this woman is doing his plan right. 15.

    1. I say that, because John McDougall has people eat starch, but limits fruit.
      Barnard limits oil, but is pretty easy about everything else, as long as people get off animal products.
      Bredesen brings oil back in, but gets rid of starches and gluten and has meat as a condiment.

      I thought I was figuring it all out, but it just started getting confusing again.

      Too many cooks in the kitchen. Or should I say doctors, researchers and nutritionists.

      Think I am going to take a mental break from it.

      1. Bredesen succeeded, but his is so all-encompassing that I am not sure if it is his oils or 15 servings of non starchy vegetables or lowering the homocysteine and other things like that.

        It feels like I need another researcher to do it without the oils and another to do it with starches and another to do it with a broader range of fruit.

        I greatly value that he succeeded at growing people’s brains back. I just am confused about oil and fat and starch and gluten again.

    2. “Is oatmeal gluten free? I will be bummed if it is.”

      Did you mean to say if it “isn’t”? Some brands do claim to be gluten free. I love steel-cut oatmeal for breakfast..

      1. Yes, “isn’t”.

        I am less confused today.

        I switched to Dr. Barnard for a while and his Alzheimer’s advice is to get rid of aluminum baking powder and get rid of vitamins with iron and copper. Increase the E Vitamin Foods. Sleep. Exercise. Take B-12.

        Turned out that the multivitamins that I take occasionally had both iron and copper. Found out that it is important for me to know not to eat baked goods, unless I know the baking powder is aluminum free, because that is what is through the roof in it.

        I need to stick with the doctors who simplify and clarify and just use studies.

        I can think about the fats, after I fix everything else is the revelation I had. Starches and Gluten…. didn’t scare me, but now I am not as confident in them, but John McDougall is reversing diseases, too.

      2. Oatmeal is inherently gluten free. However, it is often processed in plants that process wheat and other gluten containing grains, so there can be cross contamination.

  8. It is like Dr Bredesen captures all of the theories everyone was using for Alzheimer’s and I am grateful, but he didn’t do WFPB plus getting rid of homocysteine and aluminum etc.

    I say it and I am trying to lose weight and he is adding in healthy fats which I thought someone else proved weren’t that healthy either.

  9. I wonder if anyone has lived on the Bible suggestions exclusively for their diet? I mean for years. It is all there in simple terms, a plant based diet…..not a single meat mentioned.

    1. Yes, some have. I am a 4th generation vegetarian. My great-grandfather became a lacto-ovo-vegetarian in the late 1800’s, although they did not eat cheese. My grandfather was born in the 1890’s and never tasted it to his knowledge. He lived to be almost 98. He had no diagnoses except old age. My father never tasted meat and died at 94 with a diagnosis of old age. My parents and I dropped the dairy products and eggs for the most part about 40 years ago. I am now 72 and remarkably healthy. BTW, my father and grandfather were both MD’s.

  10. Dietary fiber increases survival in influenza-infected mice by setting the immune system at a healthy level of responsiveness, according to a preclinical study published May 15th in the journal Immunity. A high-fiber diet blunts harmful, excessive immune responses in the lungs while boosting antiviral immunity by activating T cells. These dual benefits were mediated by changes in the composition of gut bacteria, leading to an increase in the production of short-chain fatty acids (SCFAs) through the microbial fermentation of dietary fiber.

    From a public health perspective, influenza A infection is especially relevant because it is one of the most common viral diseases worldwide. Up to 20% of people are infected each year, resulting in substantial morbidity and mortality. In the new study, Marsland and his team found that mice were protected from influenza infection by a diet supplemented with either the highly fermentable fiber inulin or SCFAs.

    Specifically, these treatments led to both the dampening of the innate immune response that is typically associated with tissue damage, and also the enhancement of the adaptive immune response that is charged with eliminating pathogens.

  11. People in Uganda used to eat 77 grams of fiber a day?! Wow, that’s a LOT of fiber. My understanding is that the average American eats around 12 grams per day, and those on a plant-based diet average 40+. I can’t even begin to imagine what the Ugandans were eating to nearly double the American plant-based people.

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