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Climb Off the Bran Wagon
Part 5: Men only
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.'
Conclusion
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
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