The first comparison was by Burkett and Trowell, who hypothesized that dietary fiber may be responsible for the fact that Africans have significantly reduced risk of cancer than populations eating a Westernized diet. This was called the “Fiber Gap”. It turns out that rural Africans eat cooked and cooled porridge that is naturally high in resistant starch, but much less of other types of dietary fiber.
The most recent study by Stephen O’Keefe and his colleagues switched the diet between rural South Africans and African Americans living in Pittsburgh, Pa. The African Americans received a diet rich in resistant starch, while the South Africans received hamburgers and french fries, among other Western foods.
At the beginning of the study, almost half of the American subjects had polyps – abnormal growths in the bowel lining that may be harmless but can progress to cancer. None of the African volunteers had these abnormalities.
But after two weeks on the resistant starch diet from Africa, the Americans had significantly less inflammation in the colon and reduced cancer risk. While in the African group, measurements indicating cancer risk dramatically increased.