This interview with Dr. Denis Burkitt, eminent British surgeon, was conducted by Dr. Ethel Nelson during a recent colorectal-disease symposium held at the New England Memorial Hospital in Stoneham, Massachusetts, and is being published simultaneously by MINISTRY and by Life and Health. —Editors.
Q.—Dr. Burkitt, your name is known around the world by physicians, and has been associated in their minds with Burkitt's lymphoma, a cancer you first described in African children. Research on this tumor eventually led to the discovery of the Epstein-Barr virus, the first virus thought to be causative of human cancer. These discoveries opened up many avenues of cancer research. But more recently, your name has become synonymous with "fiber." Because of your interesting research in this area of nutrition, the general public is beginning to modify their diets and become really fiber-conscious. How is it that you became interested in this field?
A.—I was introduced to a retired Navy surgeon, Captain Peter Cleave, who had the concept that many of our diseases in the Western world were related to the fact that we refine our carbohydrate food, I read his book, Saccharine Disease, and had many talks with him. I realized he was on to some thing of very great importance. He had never worked overseas, but had done an enormous amount of foreign corresponding—some 12,000 or 13,000 letters, all handwritten. I had an opportunity to see whether what he said was valid by using the network I had built up with doctors all over Africa and India in my previous cancer research. Because Dr. Cleave was not in any research establishment, nor held the right appointments, nor published in the right journals, no one listened to him.
Q.—What was Dr. Cleave's actual hypothesis?
A.— He felt that many of the diseases common to our Western culture were a result of eating refined carbohydrates particularly sugar. He put a great deal of emphasis on sugar. He realized there were two sides of the coin, that there was a lack of fiber, but he focused on the concentrations of sugar and starch.
I haven't agreed with all that Cleave says. The basic concepts, I think, were brilliant. He was rather like Columbus, who made an enormous discovery. He thought he was discovering India, but really discovered something much greater.
Q.— I have been under the impression that you and Dr. Trowell had done the original work in fiber.
A.— Not at all. After my exposure to Dr. Cleave's ideas, I linked up with others who felt that a lack of fiber might be an important dietary factor. I met with Dr. A. R. P. Walker, a very fine Christian and scientist in South Africa. I linked up again with my old friend, Hugh Trowell. At that time he had been a country parson for ten years, and we have been working together for the past ten years. He is a physician who under stands nutrition. I am a surgeon and have wide contacts in the Third World. We have, with others, of course, worked on this problem together. We were the two who have been most involved in the epidemiology. There were very few who were looking at the geography. There are lots of very good workers who are doing the laboratory and clinical work on food and fiber. If I were asked whom I would give a Nobel prize to, I would give it to Peter Cleave. I would also like Hugh Trowell to get more recognition. I have had far too much recognition. I think it is partly because I already had a platform as a result of my previous work in cancer research. I was allowed to talk when I got into the field of diet because my name was known, whereas others have done better work, but they were not known.
Q.— How did you proceed with your geographical research work?
A.— In light of my own experience in Africa I was intrigued with the idea that the fiber depletion brought about by re fining processes might be responsible for some of the diseases seen today, but absent fifty years ago. I began to use the network of doctors (mainly in mission hospitals scattered throughout Africa and elsewhere) to substantiate Cleave's observations. In nearly every case we were able to confirm what he had re ported. Since he had blamed the constipation characteristic of Western culture as the underlying cause of many of our diseases, we endeavored to find out the differences in amount of stool passed in people from Western countries and in those from less developed societies. We were also interested in the time taken for swallowed radio-opaque markers to pass from mouth to anus. African or Indian villagers with minimal incidence of the diseases in question often average 500 grams of stool a day, whereas in Western countries the average is around 100 grams. Moreover, whereas food residue traverses the intestinal tract in about thirty-five hours in rural communities of the Third World countries, it takes an average of three days in young adults in the West and often more than two weeks in the elderly.
Q.— First of all, perhaps we should understand what you mean by "fiber."
A.—Fiber, very simply put, is that part of the food that passes through the small intestine undigested and unaffected by the digestive enzymes. In turn it passes on into the large bowel, where its action becomes important. The fiber binds water in the form of a gel so that on a high-fiber diet, water is held in the bowel and is not all absorbed from the bowel into the circulation. As a result, the person passes a large, soft stool. On a fiber-deficient diet, the water is not held in the intestine, resulting in production of small, hard stools. What the Western world has looked upon as being normal bowel content is actually completely pathological. If fiber were retained in our food instead of being eliminated by processing and refining, there would be no need for the laxative industry. At the moment, the people of North America are spending $250 million per year on over-the-counter laxatives, in addition to those prescribed by the medical profession. The United States is a constipated nation! If we could save the water-binding fiber in our food, the laxative industry would have to turn to making ball point pens or deck chairs, or something else!
Q.— What are some of the effects, as you see it, on the general health as the result of eating a fiber-depleted diet?
A.— Diverticulosis is the commonest disease of the large bowel. It affects 10 percent of people over the age of 40 in the United States, and about 30 percent of those over 60. Yet it is virtually unknown on the continent of Africa and in India, even in cities like New Delhi.
Q.—From my experience as a pathologist for many years in Bangkok, Thailand, I can say that we never saw diverticulosis in the indigenous population there. How ever, I'll have to admit, we never related the absence of this disease to an adequacy of fiber in the diet! I understand you also incriminate appendicitis as a disease of fiber deficiency. However, this was a very common disease in Bangkok.
A.—Appendicitis is always relatively rare in Third World countries. However, it is the first disease observed when a population begins to switch to a Western diet.
Q.—In Bangkok we did have a population eating a half-Western-half-Orientaltype diet. White bread, cakes, cookies, soft drinks, and especially ice cream are becoming quite popular and, of course, are all fiber-deficient.
A.— Appendicitis is almost unknown in people who have had no contact with modern Western culture. I have a friend who has been a missionary doctor in Uganda for thirty-seven years and is still waiting for his first case. We believe appendicitis to be caused initially by obstruction to the appendix as a result of the solid fecal content caused by a fiber-depleted diet. The infection follows the obstruction.
Gallstones are the commonest abdominal operation performed in North America. It is said that about a third of a million gallbladders are taken out in this country each year—that means 1,000 every day of the year except Sundays! Gallstones are so rare in Africa that only twice did I remove gallbladders for this condition from an African. I often say that 50 percent of my gallbladder cases in Africa were in queens. (One of my two cases was a queen; she lived and ate a bit differently from the ordinary African.)
Q.— When I first went to Thailand in 1951, I saw only an occasional case of gallstones. It was becoming a much more common disease when I left in 1968. Hiatus hernia was another condition I never saw in the Thais. I understand this is another disease on your list.
A.—Hiatus hernia affects about one in five Americans over the age of 25. It, too, is unknown in rural Africa. With the passage of a hard stool, the pressure within the abdomen rises greatly, forcing the stomach upward into the thorax through the hole in the diaphragm surrounding the esophagus. I believe this is how a hiatus hernia is formed. At the same time, this high intra-abdominal pressure forces blood out of the large veins in the back of the abdomen down into the veins of the legs and of the anal canal. This has been looked upon as an important cause in the production of varicose veins and hemorrhoids. These conditions affect nearly 50 percent of persons over 40 in the United States, but are relatively rare in Africa.
Q.— Do you believe the low incidence of coronary heart disease in the Third World countries is related to fiber in the diet?
A.— Coronary heart disease is the commonest cause of death in North America. Yet a friend with whom I co-edited a book on Western diseases re ported the first known case of coronary heart disease among the people of East Africa. Fifty years ago coronary heart disease was also very rare in the United States. Fiber in the bowel has a profound effect on the metabolism of cholesterol and bile acids, and so may be partially related not only to the production of gallstones, but also to coronary heart disease. I believe that a low-fiber diet is probably an important contributory factor in obesity and diabetes..
The commonest cancer death in the United States is now cancer of the colon—100,000 new cases of colorectal cancer a year. The slower passage of a constipated bowel content may cause prolonged contact of a carcinogen on the bowel lining, but more important, carcinogens are diluted in bulky stools and concentrated in small ones.
I might mention in this connection the experiment of feeding rats a high-fiber diet together with a poison. The rats all walked away quite happy. The experiment was repeated, using the same diet and poison, except that the diet was fiber-poor this time. After this experiment the rats lay down and died. So fiber must have some action of neutralizing poisons in the bowel, thus protecting one from dangerous substances ingested.
Q.— Do all unrefined natural vegetables and fruits contain the same amount of fiber, or are some foods better than others?
A.—Cereal grains are the best source of fiber. Not only are they better simply because they have a higher concentration of fiber than fruits and vegetables, but also because the type of fiber is better in protecting against certain dis eases. Miller's bran (from wheat) has the highest fiber content. One and a half ounces of miller's bran is equivalent to four or five ounces of whole-wheat bread. To get the same amount of fiber, one would have to eat more than a pound of white bread! Legumes and nuts are second to the grains in fiber content. Next come the tuberous root vegetables such as potatoes, carrots, turnips, and parsnips. Because of their high water content, most fruits and salad greens and cabbage have a much lower fiber con tent; however, they likewise have their specific benefits.
Q.— So you believe that diet is the villain in producing a good share of Western man's most common diseases?
A.—In the Third World, people ex pend energy. We sit behind the wheel of a car or desk. In the Third World, 80 percent of calories are unprocessed carbohydrates. Here, I am given an enormous steak with half of a small potato beside it. It would be much better to give our guests a plateful of potatoes and sprinkle a little powdered steak on top to give it flavor. In the Third World, people eat their starch and sugar in the cell wall, in which it has always been eaten throughout the history of man. We take it out. We eat food stripped of fiber.
If we compare the protein eaten in North America with that eaten in Africa, there is not much difference in amount. The World Health Organization figures show that protein in nearly every country runs about 10 to 15 percent of calories. In the Third World it tends to be vegetable protein, and ours tends to be of animal origin. That is the difference. One result of diet in our Western culture is that the amount of food taken as carbohydrate drops, and at the same time it is refined. Reciprocally, with the fall in carbohydrate, the fat intake increases. We eat four times as much fat—largely animal fat—as do those in the Third World countries. There is no diet high in fat that is not low in fiber. A high-fat diet has been incriminated in coronary heart disease, but I believe we must also look strongly at the fiber-depleted, low-carbohydrate diet as well.