[Epidemiology of colorectal cancer]

Some of the more recent contributions of epidemiology to knowledge of the causation of colo-rectal are reviewed. Geographical differences and changes in migrants suggest the importance of enviornmental (especially dietary) factors. High dietary fat is believed to stimulate increased bile secretion and thus provide a substrate for bacterial conversion to carcinogens or co-carcinogens. The association of beef consumption to colorectal cancer may relate to the fat content of beef. There is so far little direct evidence to support the alternative dietary fibre deficiency hypothesis.