Metabolic epidemiology of colorectal cancer

The distribution of cancer of the colon, particularly its infrequency in Japan, its increase among Japanese immigrants to the United States and the high rate of this disease among Americans and most Western Europeans, indicates that environmental factors are of etiologic significance in the development of this disease. Available evidence suggests that this factor is dietary in nature and is likely to be related to dietary fat intake. Studies in metabolic epidemiology have shown a correlation between dietary intake and the makeup of fecal bacteria, and between bile acids and cholesterol metabolism in the feces. A strong association has also been established between the level of anaerobic bacteria, metabolized bile acids, and degraded cholesterol and the risk of colon cancer among different populations. It remains to be shown whether this established association is causative in nature.