Studies in metabolic epidemiology have shown that the dietary intake of high fat affects the composition of the intestinal bacteria and their metabolic activity as well as the levels of certain neutral sterols and bile acids that may act as tumor promoters for the colon. A strong association has also been established between microbially modified bile acids and cholesterol metabolites and the risk of colon cancer among different populations. The patients with colon cancer had high concentrations of fecal bile acids and cholesterol metabolites compared with the controls. It remains to be shown whether this established association is causative in nature.