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Dietary Bran Fibre Increases Cancer Risk
Part 3: Other adverse effects from fibre
Tests into the supposed benefits of increasing dietary intake of fibre soon showed that there could be other harmful side-effects:
- Because it is indigestible, bran ferments in the gut and can induce or exacerbate flatulence, distension and abdominal pain. (19)
- Although it is supposed to travel through the gut at a faster rate, it does not always do so and it has been shown to cause blockages. (20)
- All the nutrients in food are absorbed through the gut wall and this takes time. It should be obvious, therefore, that if the food travels through faster, less will be absorbed. And, indeed, this is the case. Fibre is found to inhibit the absorption of zinc, (21) iron, calcium, phosphorus, magnesium, energy, proteins, fats and vitamins A, D, E and K. (22)
- Phytate associated with cereal fibre (bran) also binds with calcium, iron, (23) and zinc, (24) causing malabsorption. For example, 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. (25) Also, 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, (26) and negative balances of calcium, (27) iron, zinc, phosphorus, (28) nitrogen, fats, fatty acids and sterols thus depleting the body of these materials. (29) (A negative balance is where more is lost from the body than is absorbed, i.e. the body's stores are depleted.)
The findings, particularly in sub-paragraphs c. to e. above 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:
- Post-menopausal women stand a 1 in 2 chance of suffering from osteoporosis (brittle bone disease) and 1 in 5 of them will die as a direct result. (30) That is twice as many as many fractures as there were in the 1950s. (31) Osteoporosis is caused by a number of things, but it is basically a calcium deficiency which is at the heart of the disease. Very few surveys have concentrated on intake of any nutrient other than calcium and more research is needed on this subject. However, as the eating of bran both inhibits the absorption of calcium from food and depletes the body of the calcium it has, is it coincidence that the incidence of osteoporosis has increased by about ten percent a year for the past two decades? In England alone, a fifth of all orthopaedic beds are now occupied by patients with broken hips and the direct hospital costs alone amounted to more than £160,000,000 a year over a decade ago. (32) That figure did not include other breakages, personal costs and, of course, the pain and hardship brought on by the disease. Broken bones also require zinc for their repair, and zinc is another mineral whose absorption is adversely affected by cereal fibre.
- Calcium also plays an important role in the processes that keep normal body cells normal. Imbalances in these processes can have such adverse consequences as acute disruption leading to rapid cell death, and start other processes which lead to the deregulation we call cancer. Recent studies have shown that increases in dietary calcium may protect against cancer of the colon. (33) From this must follow that if calcium is not available because of the amount of bran in the diet, the risk of such cancer may be enhanced.
- Patients with Alzheimer's disease (senile dementia) have been 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 the disease at a much younger age, have linked it too with a lack of calcium. It is suggested that the lack of calcium causes a hormonal imbalance which allows the aluminium to penetrate the brain. (34)
- Infants can suffer a similar brain damage if fed soya based baby milk. (35) Soya based milk has a high phytate content which, as we have seen, inhibits the absorption of some minerals. (36) It is believed that a zinc deficiency so caused enhances the uptake and deposition of aluminium in the milk.
- Depression, anorexia, (37) low birth weight, (38) slow growth, (39) mental retardation, (40) and amenorrhoea are also associated with deficiencies of zinc and the first five of these are also associated with a deficiency of iron (see below).
- Vitamin deficiency diseases such as rickets are also increasing. Such diseases are common in communities where a nutrient poor, fibre rich diet is consumed, and rickets was so common in this country early in the century, that it was called the 'English disease'. All such diseases in this country should have been relegated to the past but now they are on the increase again. (41) Studies of UK Asians, in which the incidence of rickets is high, cite as the cause the Asians' low-calcium, high-cereal diet. (42)
- If there is a large intake of 'anti-nutrients' such as phytate, dietary fibre and tannins, which impair the absorption of iron, (43) and a low intake of flesh foods (another result of the diet-heart recommendations), there is a real risk of iron deficiency anaemia. And sub-optimal iron nutriture is already found in UK, USA, Canada and South Africa. (44)
- Lastly, there is an apparent relation between dietary fibre and reproductive function in the female. It affects the onset of menstruation and retards uterine growth. (45) Later it is associated with menstrual dysfunction. (46)
Although most of the experimental studies conducted using fibre consumption of 30-40g/person/day and with supplements added in the range ten to thirty grams per day (which are broadly around the levels recommended) had little adverse effect, tests on mineral availability do suggest that excessive consumption would have significant undesirable effects on mineral status. It would appear, therefore, that although a modest increase of 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 is second only to a punch in the mouth.
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