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Climb Off the Bran Wagon
Part 4: 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.
Phytate
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.
Last updated 1 April 2010
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