The relationship between smoking and lung cancer, now generally accepted throughout the world, was established by the common-sense method of comparing the incidence of lung disease with our daily habits. This naturally raises the question of what other avoidable diseases may result from our present way of life.
The most startling answer to this has come from research on the diet of Africans carried out by a small unit of the Medical Research Council in London, under the leadership of Mr. Denis Burkitt, a man already famous for his discovery of a tumor known as Burkitt’s lymphoma.
According to Burkitt, many of the most common and dangerous diseases of the alimentary canal are caused entirely by certain avoidable factors in the contemporary Western diet.
Many of the links in the chain of evidence have been on record for a number of years. The first to attract attention was a strange variation in the incidence of appendicitis.
This disease, which became suddenly prominent in Europe around the turn of the century, is to this day almost unknown in rural Africa. Burkitt himself, once a surgeon in Uganda, was puzzled by this fact. His interest was further stimulated when he found out that its incidence in city Africans was grow ing year by year, and had actually increased more than tenfold in the past two decades.
Further research showed that this was not confined to appendicitis. A similar situation existed in relation to certain other serious bowel diseases, notably cancer of the lower intestine and a condition known as diverticulitis which is similar to appendicitis but which occurs in a different part of the intestine.
These too were found to be unknown in the African peasant, common in white men, and of increasing frequency in town-bred Africans with a rising standard of living.
Why should this be? The research workers proceeded by a process of elimination. The first question to decide was whether it was a question of racial predisposition.
Various observations showed that this could not be so. Africans living a European-style life were found to be as much at risk as Europeans, and the incidence of bowel disease among black Americans was almost the same as that of white Americans.
Asians, who are genetically quite different from Africans, were found to show the African disease pattern if they were living a simple village life – but not otherwise.
Even more significantly, Japanese living in Japan showed a disease pattern of their own, somewhere between the African and the European. But the Japanese of Hawaii showed a pattern indistinguishable from that of the Americans.
The inescapable deduction from these facts is that the determining factor is something in the way of life of the more wealthy Western people which predisposes them to a disease of the lower bowel. And the most likely factor is something in the diet. It seems fairly clear that Western man is damaging his lower bowel by the food that he eats in the same way that he is poisoning his lungs by inhaling tobacco smoke.
What are the special qualities of a rural African diet that distinguish it from that of Europeans and Americans?
While there is some variation in different parts of the continent, African village food has certain common characteristics. It consists mainly of a “staple” made from some form of cereal which is cooked and made into a kind of paste or mash. In Uganda, the staple is composed of plantains (matoke), in Malawi of corn (nsima), in Nigeria of cassava (garri), in Ghana of cassava (fufu) or corn (kenkey).
Other commonly used sources of carbohydrates are millet and yams. These give the basic calories needed by the body and also stave off the pangs of hunger.
One of the most obvious facts which strikes the European about an African village meal is the bulk of it. This is because its general constituents of protein, carbohydrate, and fat are supplemented by a large amount of fiber or roughage.
The simple methods of preparation of the cereal do not refine it and remove the cellulose in the way that is usual in factory-prepared food. The meal contains a very high proportion of unabsorbable fiber which passes through the intestine unchanged.
This is reflected in the appearance of the bowel motions of rural Africans, which are copious and passed without difficulty. Constipation is almost unknown.
From the result of these investigations, Burkitt has shown that, everywhere in the world, communities living on simple high-fiber diets are protected against appendicitis or colonic disease.
Yet in cities such as Lagos, where many people are turning over from African to European food, there is an increasing incidence of such diseases, confined largely to the more prosperous members of the community.
The reason for the dangerous properties of the European diet is still a matter for speculation. It has been suggested that the reduction in the bulk of intestinal contents with a refined diet leads to changes in their bacterial content; this might well increase the risk of infection.
Changes in pressure inside the colon may have an influence in causing the weakness of the intestinal wall which is known to precede diverticulitis.
The relationship with cancer of the colon is more difficult to establish since nobody knows the cause of cancer. However, it is at least possible that an alteration in the bacterial content of the bowel might produce irritant substances that predispose towards the formation of a malignant growth.
These discoveries have raised further questions about other diseases of Western civilization.
Obesity, decayed teeth, coronary disease, and diabetes are all extremely rare in rural Africa. There is considerable evidence for the belief that all these conditions are associated with diet, particularly with the consumption of large quantities of refined sugar.
What lessons can we draw from this? Clearly, modern industrial man is never going to go back to matoke or fufu for his staple diet. What he might reasonably do, however, is to stop removing all the fiber from his cereals as he does at the present time, and to cut down as far as possible on his intake of refined sugar.
Unfortunately, the “health food” movement has been trivialized by commercial exploitation and quackery. But it is worthwhile remembering that for wholemeal flour, at least, there is a very strong body of scientific justification.