Bran is made up of the fibrous husks that cover grain seeds. It contains 12 per cent polysaccharides (cellulose, pectin and lignin) and also protein, fat, vitamins and minerals. Contrary to its common description as 'roughage' food, it is not irritating to the bowels.

Wheat bran contains 2.5 per cent cellulose (the indigestible part), which compares favourably with apples (3.6 per cent) and grapes (7 per cent). However, bran is recommended not so much for its nutritional value, but rather for the ability of its fibre to absorb water and give bulk to the faeces. It expands in the colon, stimulating bowel movement and elimination. High ­fibre diets speed up waste transit time through the colon, preventing constipation, appendicitis, diverticulosis (pockets in the colon), haemorrhoids and varicose veins, obesity and high blood pressure, cancer of the colon and coronary heart disease. With slow-moving stools, unfriendly bacteria in the colon have time to convert bile acids to carcinogens, whereas fast-moving stools facilitate bile excretion, reducing cholesterol, hypertension and heart attack. Wheat bran, oat bran and rice bran are among the most popular.

Oat bran has an outstanding soluble fibre content, much more than wheat bran, for example. In many studies, 50-100 grams a day of oat bran were found effective in lowering high cholesterol levels, selectively reducing the LDL ('bad' cholesterol) level. Oat bran was also found to reduce the need for insulin by 25-50 per cent in adult-onset diabetes. And since oat bran is bulk-forming, it can also contribute to weight loss by curbing the appetite. Available from super­markets and health food stores.

Caution

Consumption of large quantities of raw bran can result in a deficiency of minerals such as calcium unless supplements of multi-mineral tablets are taken.