There is epidemiological and experimental evidence that the ingestion of excessive amounts of fat enhances intestinal cancer formation. This may be due to the interaction of luminal steroids with the bacterial flora in the colon, forming carcinogens or promoting agents.
Increased fecal steroids induced by drugs, diet, or by mechanical means enhance intestinal tumor formation in rats given injections of azoxymethane. The effect appears to be promotional rather than initiative. Dietary fiber inhibits carcinogenesis only when the fat content of the diet is not excessive. Apparently, a quantitative relationship exists between these two dietary elements that further studies may define for prevention of cancer in humans.
Presented at the Workshop on Fat and Cancer, December 10 to 12, 1979, Bethesda, Md.