The Cholesterol Myth

Part 3: The Bran Wagon

The tragedy of science is the slaying of a beautiful hypothesis by an ugly fact. T H Huxley

The belief that regular bowel movement is important for health is very ancient. But the present theory is based on Dr. Dennis Burkitt's discovery that relatively few rural black Africans suffer from cancer of the colon. He attributed this to their relatively crude diet.

The theory was that, as fibre made food travel through the gut faster, it allowed less time for cancer-inducing agents to form. This, of course, presupposed that food became carcinogenic in the gut and there was no evidence that it did. Neither was there any evidence that moving food through the intestine at a faster rate decreased the risk of colon cancer. Moreover, the rural Africans' lifestyle was far from that of the Western city dweller: their diet is different, but also they were not exposed to so many pollutants, toxins or mental stresses. Indeed, there were many factors that could have been responsible for a difference in disease patterns. Other communities - the Mormons of Utah, for example - also enjoyed a low incidence of colon cancer yet they ate a low-fibre diet.

So the theory was unsubstantiated at the time and it was to be disproved in practice later as the rural Africans moved into towns and adopted a Western style low fibre diet. Their incidence of colon cancer has remained low and this has continued with the second generation. Nevertheless, these later findings were not publicised. Burkitt's theories caught the attention of the media. Always ready to exploit a good story, they expanded what was at best a very weak hypothesis into a treatment dogma that teaches that fibre is a panacea for all manner of illnesses.

Commercial interests were quick to see the potential in the recommendation and jump on the bran wagon. Burkitt's recommendation was based on vegetable fibre, but bran (cereal fibre) has a far higher fibre content and bran was a practically worthless by-product of the milling process that, until then, had been thrown away. Almost overnight, it became a highly priced profit maker. Although totally inedible, backed by Burkitt's fibre hypothesis, bran could now be promoted as a valuable food. But Dr. Hugh Trowell, Burkitt's partner and another strong advocate of dietary fibre, stated in 1974 that:

"A serious confusion of thought is produced by referring to the dietary fibre hypothesis as the bran hypothesis, for many Africans do not consume cereal or bran"

Fibre and coronary heart disease

The idea that fibre could protect against heart attacks was hypothesised by Trowell in 1972, again based on research on rural Africans. The dietary intervention trials mentioned earlier, however, concluded that increasing dietary fibre had no beneficial effect on heart disease.

Fibre and other diseases.

It may be useful at this stage to consider the claims for fibre in curing or preventing other diseases. For example, bran has been a popular way to manage irritable bowel syndrome (IBS) for about thirty years, despite the fact that no placebo-controlled study of bran in IBS has yet shown any convincing beneficial effect. A study, published in 1994, found that while fruit fibre was effective, bran only made the situation worse. Far from being a cure for IBS, they found that it was the bran that was causing it! Bran also caused bowel disturbances, abdominal distension and pain.

Moreover, there is no direct evidence that an increase of fibre by itself will prevent or cure the other diseases. With respect to colon cancer, Burkitt's theory was questioned with the suggestion that the low cancer rates in rural Africans may be due to their high early death rates from other causes.

There is also a growing scepticism in the USA that lack of fibre causes cancer; some studies even suggesting that a fibre-enhanced diet increases the risk of colon cancer.

Other adverse effects

Tests into the supposed benefits of dietary fibre soon showed that there could be other harmful side effects. All the nutrients in food are absorbed through the gut wall and this takes time. Fibre, by speeding food through the gut faster so that less nutrients are absorbed, inhibits the absorption of iron, calcium, phosphorus, magnesium, energy, proteins, fats and vitamins A, D, E and K. This happens with all types of fibre although with a normal Western-style, nutrient-rich diet, the loss caused by vegetable fibre intake is unimportant. More importantly, phytate found in cereal fibre (bran) also binds with calcium, iron and zinc making them indigestible, which in turn causes malabsorption. One study, for example, showed that subjects absorbed more iron from white bread than from wholemeal bread even though their intakes of iron were fifty percent higher with the wholemeal bread. Bran has also been shown to cause faecal losses of calcium, iron, zinc, phosphorus, nitrogen, fats, fatty acids and sterols, thus depleting the body of these materials.

These findings are a cause for concern in several sections of the population who are at considerable risk from eating too much fibre - and bran fibre in particular:

The incidence of osteoporosis (brittle bone disease) is increasing and now affects one in two post-menopausal women, one in five of whom will die as a direct result. Osteoporosis is also increasingly affecting men. Osteoporosis is caused by several factors, but lack of calcium is the basic problem. Bran both inhibits the absorption of calcium from food and depletes the body of the calcium it has. Moreover, zinc, which bones need to heal, is another mineral whose absorption is adversely affected by bran.
Sufferers from Alzheimer's Disease (senile dementia) are found to have abnormal amounts of aluminium in their brains. Tests on the people of Guam and parts of New Guinea and Japan, who get Alzheimer's disease at a much younger age, suggest that it is lack of calcium, causing a hormonal imbalance that permits the aluminium to penetrate the brain.
Infants may suffer similar brain damage if fed soy-based baby milk as this too has a high phytate content, inhibiting the absorption of zinc, which is essential for proper brain development.
Vitamin deficiency diseases such as rickets that were common in Britain until a diet high in dairy products and meat was advocated are on the increase again. The situation is getting so bad here that doctors suggest that vegetarian-based fad diets should be classified a form of child abuse.
In the UK, USA, Canada and South Africa the intake of 'anti-nutrients' such as dietary fibre that impair the absorption of iron, accompanied by a low intake of meat (another result of the diet-heart recommendations), is producing a real risk of iron deficiency anaemia.
Depression, anorexia, low birth weight, slow growth, mental retardation , and amenorrhoea are associated with deficiencies of zinc and the first five of these are also associated with a deficiency of iron.
Lastly, excess fibre affects the onset of menstruation, retards uterine growth and, later, is associated with menstrual dysfunction .

Because of the phytate, Professor David Southgate, arguably the world's leading authority on the effects of fibre, concludes that infants, children, young adolescents and pregnant women whose mineral needs are greater should be protected from excessive consumption of fibre.

Writing of the colon cancer risk, Drs. H. S. Wasan and R. A. Goodlad of the Imperial Cancer Research Fund stated in 1996:

"Until individual constituents of fibre have been shown to have, at the very least, a non-detrimental effect in prospective human trials, we urge that restraint should be shown in adding fibre supplements to foods, and that unsubstantiated health claims be restricted." . . . "Specific dietary fibre supplements, embraced as nutriceuticals or functional foods, are an unknown and potentially damaging way to influence modern dietary habits of the general population."

Until fibre can be shown not to be detrimental they suggest that

"restraint should be shown in adding fibre supplements to foods, and that unsubstantiated health claims should be restricted".

January 1999 saw the publication of the largest trial into the effects on fibre on colon cancer ever conducted. After studying 88,757 women for sixteen years, doctors at the Brigham and Women's Hospital and Harvard Medical School say that

"No significant association between fiber intake and the risk of colorectal adenoma was found." . . . "Our data do not support the existence of an important protective effect of dietary fiber against colorectal cancer or adenoma."

Summary

Bran is bad news. While there is not too much harm from fruit fibre, the usual bran that is pushed at us - wheat bran - should be avoided like the plague it is.

References:

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Return to Part 2: Fats and Heart Disease | Part 4: The Dangers of Low Blood Cholesterol

See also www.Cholesterol-and-Health.org.uk, an easy to read website about this whole topic from what cholesterol is, why you need it, and how it is made in the body, to what happens if you take cholesterol-lowering drugs such as statins.

Last updated 18 September 2000

"One must attend in medical practice not primarily to plausible theories but to experience combined with reason." Hippocrates

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