Is the Fiber Theory Wrong?

Michael Greger M.D. FACLM · December 18, 2015 · Volume 28

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The extraordinarily low rates of chronic disease among plant-based populations have been attributed to fiber, but reductionist thinking may lead us astray.

Discuss

Transcript

Fiber-containing foods may not only help prevent heart disease, but 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 that don’t. But what if we really don’t want to have a heart attack in the first place? If seven grams of fiber gets us a 9% reduced risk, would 77 grams a day drop our risk 99%? Well, that’s about what they used to eat in Uganda, a country in which coronary heart disease, our #1 killer, was almost non-existent.

Heart disease was so rare among those eating these traditional plant-based diets, there were papers published like this: “A case of coronary heart disease in an African.” After 26 years of medical practice, they finally recorded their first case of coronary heart disease in a judge consuming a partially Westernized diet, having fiber-free foods like meat, dairy, and eggs displace some of the plant foods in his 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, like infections, but when they reached middle age, they had the best survival, thanks in part to our number one killer being virtually absent. Of course, now, diets have Westernized across the continent, and it gets to now be their #1 killer as well. From virtually non-existent to an epidemic.

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

The ‘dietary fiber hypothesis,’ first proposed in the 70’s, zeroed in on fiber as the dietary component that was so protective against chronic disease. And since then, evidence has certainly accumulated that those who eat lots of fiber appear 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. So, maybe all these studies showing fiber is good are really just showing that eating lots of unrefined plant foods is good.

Fiber is but one component of plant foods, and to neglect the other components—like 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 for this 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 that we should go back to eating whole plant foods, he was so convinced fiber was the magic component, his top recommendation was to eat whole grain bread—but they never used to eat any kind of bread in Uganda— and sprinkling some spoonfuls of wheat bran on your food.

But 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, maybe it was 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 instead emphasized 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 in this aisle for their fiber, instead of this aisle.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.

Please consider volunteering to help out on the site.

Sources

Acknowledgements

Images thanks to Eric Allix Rogers and rick via Flickr, and Elizabeth Magner.

Fiber-containing foods may not only help prevent heart disease, but 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 that don’t. But what if we really don’t want to have a heart attack in the first place? If seven grams of fiber gets us a 9% reduced risk, would 77 grams a day drop our risk 99%? Well, that’s about what they used to eat in Uganda, a country in which coronary heart disease, our #1 killer, was almost non-existent.

Heart disease was so rare among those eating these traditional plant-based diets, there were papers published like this: “A case of coronary heart disease in an African.” After 26 years of medical practice, they finally recorded their first case of coronary heart disease in a judge consuming a partially Westernized diet, having fiber-free foods like meat, dairy, and eggs displace some of the plant foods in his 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, like infections, but when they reached middle age, they had the best survival, thanks in part to our number one killer being virtually absent. Of course, now, diets have Westernized across the continent, and it gets to now be their #1 killer as well. From virtually non-existent to an epidemic.

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

The ‘dietary fiber hypothesis,’ first proposed in the 70’s, zeroed in on fiber as the dietary component that was so protective against chronic disease. And since then, evidence has certainly accumulated that those who eat lots of fiber appear 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. So, maybe all these studies showing fiber is good are really just showing that eating lots of unrefined plant foods is good.

Fiber is but one component of plant foods, and to neglect the other components—like 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 for this 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 that we should go back to eating whole plant foods, he was so convinced fiber was the magic component, his top recommendation was to eat whole grain bread—but they never used to eat any kind of bread in Uganda— and sprinkling some spoonfuls of wheat bran on your food.

But 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, maybe it was 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 instead emphasized 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 in this aisle for their fiber, instead of this aisle.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.

Please consider volunteering to help out on the site.

Images thanks to Eric Allix Rogers and rick via Flickr, and Elizabeth Magner.

Doctor's Note

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

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

Wait a second, though, didn’t I just have a video saying you should specifically look for fiber? The Five to One Fiber Rule is just 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: Dr. Burkitt’s F-word Diet

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