Climb Off the Bran Wagon
Perhaps one reason for the wide acceptance of the suggestion
that fibre is an important, if not essential, dietary component is
that it had the enthusiastic support of commercial interests.
PROFESSOR JOHN YUDKIN
With cereals comes bran (cereal fibre). We have been urged for generations to eat fibre to prevent and cure many bowel and other health conditions. However, research shows that, while vegetable fibre may be relatively harmless, bran increases the risk of many of the conditions it is promoted to prevent and cure — and a lot more as well.
The belief that regular bowel movement is important for health is very ancient. In 1932 a 'New Health' movement was promoted in which people were urged to include plenty of roughage in their diets and it was hoped then that the prompt passing of stools after each substantial meal would reduce the incidence of intestinal diseases.1 Thirty years later Dr Dennis Burkitt, while working as a doctor in Africa, discovered that there were far fewer cases of colon cancer among rural black Africans than among Europeans and Americans. He attributed this to the Africans' relatively crude diet.2 The theory was that fibre — that part of a vegetable which passes undigested through the human gastrointestinal tract — hastened the passage of the bowel contents thus allowing less time for cancer-inducing agents to form. This, of course, presupposed that food became carcinogenic in the gut; 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 cancer.
So the theory was unsubstantiated at the time and it was to be disproved later when the rural Africans moved into towns and adopted a western-style, low fibre diet, and it was noticed that they continued to have a low incidence of colon cancer. This pattern has also continued with the second generation. It should also be noted that the rural Africans' lifestyle is quite different from that of the western city dweller: their diet is different in that their energy intake is lower and they eat less protein, fat and sugar; they are also not exposed to so many pollutants, toxins or mental stresses and any of these factors could be responsible for the difference in disease patterns. Other studies have also shown that there are western communities (the Mormons of Utah, for example) who also enjoy a low incidence of colon cancer but eat a low fibre diet.3 Nevertheless, the later findings were not publicized; Burkitt's theories caught the attention of the media who, always ready to exploit a good story, expanded what was at best a very weak hypothesis into a treatment dogma which teaches that fibre is a panacea for all manner of illnesses.4
Commercial interests were quick to see the potential in the recommendation. Although Burkitt's recommendations were based on vegetable fibre, bran has a far higher fibre content than vegetables and bran was a practically worthless by-product of the milling process which, until then, had been thrown away. Bran is quite inedible — there is no known enzyme in the human body that can digest it; nevertheless, backed by Burkitt's fibre hypothesis, commercial interests could now promote it as a valuable food. Virtually overnight, it became a highly priced profit maker. The late Dr John Yudkin, Professor of Nutrition and Dietetics at London University, pointed out that 'perhaps one reason for the wide acceptance of the suggestion that fibre is an important, if not essential, dietary component is that it had the enthusiastic support of commercial interests.'5
Dr Hugh Trowell, Burkitt's partner and another strong advocate of dietary fibre, confirmed this in 1974, saying 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 but remain almost free of constipation, irritable bowel syndrome and diverticular disease.'6
Bran is the tough outer covering of cereal grains. Every civilization in history has devised methods and implements solely for the purpose of separating bran from the grain so that they would not have to eat it.
Fibre and colon cancer
Animal studies have variably suggested that dietary fibre reduces risks, increases risks, or has no effect on bowel cancers. Epidemiological studies on humans have also found that intakes of dietary fibre are either protective, or have no effect; there is also a growing scepticism in the US that lack of fibre causes cancer; some studies have even suggested that a fibre-enhanced diet may increase the risk of colon cancer.7
Figure 1: Colorectal cancer and fibre intake
In the mid-1980s dietary fibre was shown to increase the risk of colon cancers.8 In 1990 the British Nutrition Foundation admitted that the hypotheses that irritable bowel syndrome (IBS), diverticulosis and colorectal cancer were caused by a deficiency of fibre had not been substantiated; and neither had claims that fibre might protect against diabetes, obesity and CHD.9 The Seventh King's Fund Forum on Cancer of The Colon and Rectum commented that: 'cereal fibre does not offer protection against cancer.'10
In 1995 Dr M. Inoue and colleagues published an investigation of cancers at several colorectal subsites: ascending, transverse, descending, sigmoid, and rectum, within a Japanese hospital environment. They concluded that loose or soft faeces are a significant risk factor for cancer at these sites.11 But bran loosens and softens faeces — that's why it is recommended.
The following year Drs H. S. Wasan and R. A. Goodlad of the Imperial Cancer Research Fund showed that bran can increase the risk of colorectal cancers.12 'Many carbohydrates,' they said, 'can stimulate epithelial-cell proliferation throughout the gastrointestinal tract,' and concluded: '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.' This study spawned several critical letters. It comes as no surprise that half were from people connected with the breakfast cereal industry.13
The results of a very large, long-term trial also suggest that, contrary to popular belief, high dietary fibre intake does not protect against colorectal cancer.14 Researchers at Harvard Medical School and the Dana-Farber Cancer Institute, both in Boston, Massachusetts, studied 88,757 women over 16 years. They say: 'no significant association between fiber intake and the risk of colorectal adenoma was found.' But there was what they call an 'unexpected' finding, in that, according to their data, a high consumption of vegetable-derived fibre was actually 'associated with a significant increase (35%) in the risk of colorectal cancer'.
That fibre increased the risk of colon cancer was confirmed six years later by a large analysis of 17 studies of the effect of dietary fibre on colorectal cancer.15 Although the abstract of the study said that people with the highest intakes of fibre had a reduced risk of colon cancer, that was exactly the opposite of what the study data showed. Using the study's Table 3, dividing the number of cases of colorectal cancer by person-years of exposure, and multiplying by 10 to obtain number of cases per 10-person-years, since the mean study length was about 10 years, the effect was not a reduction in cancers as fibre intake increased but an increase. This is graphically illustrated in Figure 1. Lead researcher, Yikyung Park, said that 'There are more questions to be answered but clearly this adds to the growing body of evidence finding that high fiber intake does not lower the risk of colorectal cancer.'
Fibre and heart disease
The idea that fibre could protect against coronary heart disease was hypothesized by Dr Trowell in 1973,16 again based on research on rural Africans. But while pectin, guar gum, fruit and vegetables lowered blood cholesterol levels, they were not lowered by wheat fibre (bran), or a diet containing wheat and whole maize. There is little evidence that fibre of any type is effective in reducing levels in the blood of triglycerides or other fats.
The paucity of evidence, however, did not stop COMA (the Committee on the Medical Aspects of Food Policy) seeing advantages in compensating for a reduced fat intake with increased fibre-rich carbohydrates, although it makes no specific recommendations. On dietary fibre, the report at paragraph 4.3.3 says: 'However, epidemiological data suggest that cereal fibre is protective against coronary heart disease.' Yet COMA's own reference for that statement says: 'However, wheat fibre appears to have no consistent effect on plasma cholesterol or triglycerides in man.' The report also says at 4.3.5 that: 'the protective effect in relation to coronary heart disease has not been adequately tested.'
Oat bran — the wonder fibre?
Oat bran is regarded as a 'healthy' cholesterol-lowering food. It is advertised with statements such as 'recent medical research shows that oat bran could actually lower your cholesterol level.' This is based, apparently, on an experiment conducted at Northwestern University, Evanston, Illinois, in 1986, which involved only 208 subjects, lasted just six weeks and whose results were not statistically significant.17 Despite this, an oat bran campaign in the US saw sales of oat bran cereals increase 240% by 1989.
More recent medical research has come up with very different findings. Results of an American study into the effects of oat bran showed that oat bran was not the cure-all it had been claimed to be — just another example of dietary advice that is 'without foundation' and 'verging on quackery'.18 In this test, people were fed 100 grams of oat bran per day (three times the recommended dose), the placebo (control) group having 100 grams of a white flour, low-fibre placebo. There was no appreciable difference in blood cholesterol levels between the two groups. The authors said: 'Some dietary fibres do bind bile acids and thus may have a cholesterol-lowering effect similar to that of the bile-acid-sequestrant drugs. However, many experiments, both in outpatients and in metabolic wards, have failed to demonstrate that wheat bran does, in fact lower plasma cholesterol levels.' They then said that: 'oat bran had no effect over and above that of the wheat placebo. It did, however, produce gastrointestinal rumbling and some discomfort.'
Another American study published the same year also had similar findings, and concluded: 'As we also found, low-fibre products can achieve the same result with fewer gastrointestinal side effects.'19
The following year oat bran was tested in people with high blood cholesterol levels.20 Using 30, 60 and 90 grams of oat bran per day, they found that it made not the slightest difference either to total cholesterol levels or to levels of low density lipoprotein (LDL).
That rules out cereal fibre. Could other plants that also contain fibre be better?
Fruit and vegetables contain quite small amounts of fibre (see Table 1) so that if a significantly larger amount is to be eaten, this will have a dramatic effect on the volume of food consumed. Thus the advice to increase fibre in the diet, if we are to use 'natural' sources, must involve a substantial change to the diet as a whole. And that is likely to be unpopular or we would be eating it already.
Table 1: Amounts of fibre in typical foods
Food g/100 grams g/100 kilocalories
Apples, raw 2.0 4.3
Beans, haricot, boiled 7.4 8.0
Cabbage, winter, boiled 2.8 18.7
Carrots, young, boiled 3.0 15.0
Potatoes, new, boiled 2.5 2.6
Plums, raw 2.9 8.0
We know, then, that an increase of the right kind of fibre in the diet may lower blood cholesterol. The important question is: will it also lower the risk of heart disease? The various multifactoral intervention trials tested this and all had to conclude that increasing dietary fibre had no effect on heart disease. In addition, there is really no direct evidence that an increase of fibre by itself will prevent or cure any of the other diseases.
Clearly there are two sides to this debate and claims of benefit are by no means proven. That, of course, does not stop a variety of commercial interests from jumping on a very lucrative 'bran wagon'.
When the American Heart Association published its dietary recommendations in 1982, the US National Cancer Institute (NCI) and Kellogg's got together to promote All-Bran.21 But by making such health claims, Kellogg's effectively turned All-Bran from a food into a drug — and drugs must be approved by the Food and Drugs Administration (FDA). This gave the FDA a problem as the NCI had already given its blessing to All-Bran. They have an even bigger problem now because of the lack of evidence that fibre protects against cancer.
Fibre pills for obesity
In a UK pharmacist, Boots the chemist, I saw fibre pills which, their label claimed, would reduce obesity. Each pill contained 0.2 grams of fibre and the recommended dose was four to six pills before each meal or when one feels hungry. Its makers claimed that fibre stays in the stomach longer and so wards off the pangs of hunger. There are two points to be made here: firstly, that the theory on which the fibre hypothesis is based is that it does not stay in the gut longer but that it moves through quickly and, secondly, that even if it did stay in the stomach, around one gram (five pills) would have no effect whatsoever. It is about the amount of fibre one would find in one dried prune.
Fibre and mineral absorption
The fibre hypothesis was based on the fact that an increase in dietary fibre moved food through the gut faster. However, all the nutrients in food are absorbed through the gut wall and this takes time. If the food travels through faster, there is less time for its absorption and consequently less is absorbed. Because of this, all fibre, whether it is from fruit, vegetables or cereals, inhibits the absorption of such nutrients as zinc,22 iron, calcium, phosphorus, magnesium, energy, proteins, fats and vitamins A, D, E and K.23 Now this doesn't matter too much if you eat a good nutrient-dense diet which contains plenty of these nutrients. But there is another problem with cereal fibre (bran): its phytate content.
The American Journal of Clinical Nutrition is arguably the most important journal of nutrition. In 1992 Professor Harold Sandsted, its Editor-in-Chief, noted that:
'the evidence seems overwhelming that high intakes of fiber sources that are also rich in phytate can have adverse effects on mineral nutrition of humans . . . In view of the data, it appears that some health promoters who suggest that [we] should consume 30-35 g dietary fiber daily either have not done their homework or have simply ignored carefully done research on this topic.'24
What he was talking about was the phytic acid that cereals, soya and other legumes have in their husks. It is well known that by this mechanism wholegrain cereals decrease the absorption of minerals and that this leads to a variety of deficiency diseases in both developed and undeveloped countries.
The minerals mostly affected by phytic acid are calcium, iron25 and zinc.26 For example, subjects absorbed more iron from white bread than from wholemeal bread even though their intakes of iron were 50% higher with the wholemeal bread.23 And while white bread must have added calcium, the law does not require it of wholemeal bread.
Bran fibre has also been shown to cause faecal losses,27 and what the medical profession calls 'negative balances', of calcium,28 iron, zinc, phosphorus,29 nitrogen, fats, fatty acids and sterols. A negative balance is where more is lost from the body than is absorbed. What this means is that bran causes a loss of these nutrients from your body.30
Dr E. J. Moynahan suggested that: 'Any substantial return to a high-fibre diet may lead to a reversal to the situation that obtained a century ago . . . Apparently, therefore, the amount of fiber must be strictly limited or the cereals fortified not only with calcium but also with iron and zinc as well, if this is to be avoided.'31
This prophecy turned out to be well founded as tests soon showed that there could be harmful side effects; since the advent of 'healthy eating', we have seen the re-emergence of many previously rare deficiency diseases.
Although most of the experimental studies conducted using fibre consumption of 30-40 grams/person/day and with supplements added in the range 10 to 30 grams/day (which are broadly around the levels recommended) showed little adverse effect, tests on mineral availability did suggest that excessive consumption would have significant undesirable effects on mineral status. It would appear, therefore, that although a modest increase in vegetable fibre would probably not have any significant adverse effects, provided that there were adequate amounts of proteins, minerals, etc in the diet, any advice must be given in such a way as to prevent the excessive intake of phytate associated with cereal fibre (bran). Incidentally, as a breaker of teeth, granary bread, made with whole wheat seeds, is second only to a punch in the mouth.
So why on earth are we still told the opposite?
Burkitt and Trowell were firmly committed to the United States' McGovern Committee's dietary goals, namely the replacement of animal products with grains as a way to 'prevent cancer and heart disease' and to 'forestall world hunger'. Burkitt's writings on dietary fibre led to calls for increased amounts of whole grains in the American diet in order to prevent colon cancer and other diseases of the intestinal tract. Dietary fibre soon became a household word, and America embraced the oat bran fad.
What Americans failed to recognize was that Africans do not eat their grain foods as we do in the West, in the form of quick-rise breads, cold cereals, energy bars and pasta; they eat them as a sour or acid porridge. Throughout Africa, these porridges are prepared by the fermentation of maize, sorghum, millet or cassava. Preparation in the home begins with washing the grains, then steeping them in water for up to three days. The grain is then drained and the water discarded. Soaked grains are wet milled and passed through a sieve. Whatever is left in the sieve is discarded. In other words, the Africans throw away the bran. The smooth paste that passes through the sieve may undergo further fermentation. Soaking water that rises to the top is discarded and the slurry is boiled to make a sour porridge. Sometimes the slurry is allowed to drain and ferment further to form a gel-like substance that is wrapped in banana leaves, making a convenient energy bar that can easily be carried into the fields and consumed without further preparation.32 Often sour porridges are consumed raw as 'sorghum beer', a thin, slightly alcoholic slurry that provides lactic acid and many beneficial enzymes.
Acid porridges made from grains are far superior to western grain preparations. Fermentation increases mineral availability by neutralizing the phytic acid, it increases vitamin content, predigests starches and neutralizes enzyme inhibitors. Insoluble fibre can cause pathogenic changes in the intestinal tract unless properly soaked in an acid medium.33 Oat bran, which is high in phytic acid as well as related bran products, can cause numerous problems with digestion and assimilation, leading to mineral deficiencies, irritable bowel syndrome and auto-immune conditions such as Crohn's disease. Case control studies indicate that consumption of cereal fibre can be linked to detrimental effects related to colon cancer formation.34
Another fermented food consumed throughout Africa, and universally ignored by most investigators, is a paste made from dried shrimp and hot peppers. This strong, spicy condiment is a rich source of fat-soluble vitamins. Shrimp has ten times more vitamin D than organ meats, and vitamin D protects against cancer of the colon and rectum, neurological disorders such as multiple sclerosis, and osteoporosis 35 — all of which are extremely rare among Africans.
Several researchers have noted that, along with sugar, tea and white flour, vegetable oils made from peanuts, cottonseed or soya have made inroads into the African diet. What these oils replace is highly saturated palm oil, which has been a staple in Africa for millennia. This has resulted in overall decline in the consumption of saturated fat in Africa. Like vitamin D, saturated fats play a role in protecting the intestinal tract from cancer and other diseases, and in preventing osteoporosis.
Doctors who write about diet are severely limited by their lack of familiarity with basic cooking methods. One gets the distinct impression in reading Dr Burkitt's book that none of the authors had actually tasted traditional African food, let alone observed its preparation. Otherwise they would have known that Africans customarily cook calves' feet to make broth for soups and stews. Often dried fish and shrimp are added to these stews, along with meat, peanuts and vegetables. Pieces of gristly calves' feet go into the pot along with everything else and are eaten with relish. Americans are just beginning to discover the health benefits of beef cartilage; Africans have enjoyed such benefits for centuries.
Professor David Southgate is a world-renowned expert on dietary fibre. He concluded that the effects of excessive intakes of dietary fibre on calcium, iron and zinc absorption would be particularly undesirable for infants, children and young adolescents, and recommended that dietary fibre intakes in those groups should be separated from those for the general adult population and given on a body-weight basis.36 To them should be added pregnant women and post-menopausal women whose mineral needs are greater and who should also be protected from excessive consumption of fibre.
The advice given by dieticians, nutritionists and doctors appears to include no caveats concerning age, sex or body weight. Indeed, the impression given by them all is that we should all eat as much fibre as we can tolerate. The British Medical Association in its publication The Slimmers' Guide, even recommended bran as a good source of calcium!37 Not unnaturally, the makers of breakfast cereals and wholemeal breads stress the goodness contained in their products by virtue of the high bran content. Yet the only members of the population who may eat these in any quantity with relative impunity are adult men.
Can ripping intestinal cells really be beneficial?
Although they have pushing bran for many years to facilitate the movement of faecal material through the gut, nutritionists had no idea how it worked until scientists at the Medical College of Georgia found the answer in 2006.38 It seems that as the rough, bulky bran makes its way down the gastrointestinal tract, it scratches and tears cells in the gut wall. According to cell biologist, Dr Paul L. McNeil: 'What we are saying is this banging and tearing increases the level of lubricating mucus. It's a good thing.'
That consuming roughage increased mucus production was known years ago; Dr McNeil discovered that cell injuries and repairs occur when we eat. The new research tied the two together. 'These cells are a biological boundary that separates the inside world, if you will, from this nasty outside world. On the cellular scale, roughage, such as grains and fibers that can't be completely digested, are a mechanical challenge for these cells,' said Dr McNeil. In what he and colleague, Dr Katsuya Miyake, view as an adaptive response, most of these cells rapidly repair the damage and, in the process, excrete even more mucus, which provides some cell protection as it eases food down the gut. The scientists aren't certain how many times cells can take this punishment, but they suspect turnover must be high because of the constant injury. Acidic substances, such as alcohol and aspirin, can produce so much damage that natural recovery mechanisms can't keep up. But they doubt a roughage overdose is possible.
However, why would you want your intestinal lining stripped in such a sandpaper-like manner, potentially exposing the underlying, immature cells to the assaults they may not cope with well? Inflammation can start a cancer. Could this abrasion possibly start colon cancer? Or, perhaps, cause pre-cancerous changes under stress from bacterial metabolites or 'toxins'?
I would have thought that mucus cells could play their normal role without being ripped to shreds. And this benefit of bran (if it can be called a benefit) applies only to the large intestine (colon). What adverse effects would such rough treatment do to the delicate villi which line the small intestine or the wall of the stomach?
Incidentally, I haven't eaten any cereal fibre, and very little vegetable fibre either, for many years. I have no trouble at all keeping 'regular.'
What we have is evidence that some forms of vegetable fibre — but not bran — have been found to lower blood cholesterol levels, but that this has had no effect on heart disease mortality or morbidity rates (which is not surprising, as lowering blood cholesterol levels in the general public by any means has not proved beneficial); and that the consumption of fibre — and bran in particular — may be hazardous.
There is a very real danger that mothers of growing families, perhaps already obsessed with slimming, will spend much of their limited food budgets on heavily advertised, expensive, fibre-rich breakfast cereals and biscuits. With the balance tipped away from nutrients, their children could well suffer in terms of growth which can have serious long-term consequences apart from those already mentioned.
There is also a similar danger of malnutrition in the elderly who are also at risk from hypothermia. On both sides of the debate there is agreement that the recommendations on both fibre and fats will not benefit the over-60s. But one only has to look in the supermarket shopping trolleys of elderly women to see packets of highly priced, nutrient poor commodities such as bran flakes, when their pensions would be better spent on highly nutritious and energy-rich food such as eggs.
It seems unlikely that eating bran is of benefit to any section of society. There is a limit under which bran may not be harmful — but no ready way to know what that limit is. Therefore, it is much safer for you to avoid bran than to try to gauge what your safe limit might be. And if you do suffer from constipation, you would be better advised to drink more water. About four pints a day should do it.
As a postscript, I am informed that, ironically, Dr Burkitt died of colon cancer.39
Last updated 1 April 2010