Does a high fibre diet prevent disease?

All doctors (and probably most non-doctors) have heard of Burkitt’s lymphoma, a type of cancer found primarily in children living in malaria-endemic areas in Africa. Denis Burkitt was the first person to describe the disease, and also the first person to propose that there was an environmental cause (now known to be simultaneous infection by both malaria and Epstein-Barr virus).

Most doctors probably don’t know that Denis Burkitt is also almost single-handedly responsible for the now widespread belief that dietary fibre is an important part of a healthy diet. Interestingly, Burkitt developed his ideas about dietary fibre after corresponding with a less well known doctor called Thomas Cleave (who hasn’t been allowed to give his name to any diseases).

Cleave was interested in the connection between diet and disease, and had noticed how the transition from a traditional diet to a modern diet, rich in refined carbohydrates, was associated with a massive increase in a large number of diseases, including cancer, diabetes, heart disease, and obesity. He even wrote a book on the subject. Burkitt was introduced to Cleave in the late 1960’s by epidemiologist Richard Doll (himself famous for discovering that smoking causes lung cancer).

Burkitt was deeply affected by Cleave’s ideas, and in particular his conception that all the “diseases of civilization” had a single underlying cause, but he took the data and went off in a different direction with it. While Cleave believed that it was the refined carbohydrates in the modern diet that were causing harm, Burkitt came to believe instead that it was the absence of dietary fibre that was responsible. Since refined carbohydrates are by definition low in dietary fibre, the two things track together perfectly, and it becomes almost impossible to say from observational data which is the causative factor and which is the confounder.

There was a big fly in the ointment of Burkitt’s hypothesis from the start, however, and that was the fact that the Maasai tribespeople in Kenya and Tanzania, who lived on a diet consisting almost entirely of meat, milk, and blood, showed none of the diseases of modern civilization, even though they had virtually no fibre in their diet. Burkitt, who spent much of his career in Africa, was well aware of this fact, but seemingly chose to ignore it because it didn’t fit his hypothesis.