Dietary Fibre: Taking the Rough with the Smooth

Medicine is as subject to the whims of fashion as the world of haute couture. Few things date as quickly as last year’s health craze. In the 1960s doctors discovered the virtues of roughage, and within a matter of months the health seeking multitude jumped on the bandwagon and switched to eating a high fibre diet. Now we’ve moved on to other fads and isms. Forty years ago breakfast cereals were promoted as being high in bran, now they’re sold on the strength of their added nutrient content. Yet in the intervening years there’s been no change in our biochemistry or nutritional needs. The roughage we get from the cellular walls of plants isn’t a source of nourishment, but it’s still acknowledged to be an essential ingredient of a well-adjusted diet.

The fibre furore began when researchers noted that people suffered an increase in bowel disease when they switched from eating traditional native foods and adopted a highly processed Western diet. Africans who settled in America experienced a greatly increased risk of constipation, irritable bowel syndrome and colonic cancer when they stopped eating maize, millet and beans and took to eating ‘civilized’ foods, like sugar, doughnuts, white bread and jam. Animals like cows and rabbits can break down the cellular walls of grasses and plants but we can’t, because we lack the enzyme systems necessary to digest cellulose. As a result fibrous plant material passes through our intestines largely unchanged, absorbing water as its goes. This increases the size and softness of the stools, and accelerates the speed at which they pass through the gut. Forty years ago it was revealed that the average weight of the stools of an English public school boy was more than four times less than that of African villagers, and took more than twice as long to pass through the gut. Instead of being soft, as nature intended, they were often rock hard. This explains our increased liability to constipation – often described as ‘the white man’s disease’ – and also our increased risk of bowel cancer, because the slower the transit time of faecal material the longer the intestinal walls are exposed to dietary toxins and carcinogens.

The dietary roughage campaign received a further boost when the Royal College of Physicians announced that eating roughage helped to prevent obesity. In 1982 Audrey Eyton published The F-Plan Diet, a slimming regime which became a publishing sensation, selling millions of copies around the world in numerous editions. Now the book is yesterday’s news, with second-hand copies available on the web for 50p. Today doctors agree that diets rich in roughage are associated with a reduced risk of chronic ailments like heart disease, obesity, late-onset diabetes and certain types of cancer. (A study carried out by a team of researchers at the University of Sheffield has shown that women who have the highest intake of fibre cut their breast cancer risk by half.) The message seems clear. If we want to maintain a high level of health, and reduce the risk of succumbing to the chronic diseases of Western civilization, we need to eat less concentrated, processed food and step up our intake of fresh fruit and vegetables, eaten either raw or lightly cooked.

Key words: Roughage; Audrey Eyton; Heart Disease; Breast Cancer.
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