Dietary promotion of carcinogenesis.

Environmental influences are thought to be largely responsible for the marked geographical differences in cancer mortality observed in epidemiological studies. Diet has been implicated as a significant environmental variable because certain dietary constituents, such as fat, show a positive correlation with mortality from cancer at specific sites such as breast and colon. Similar correlations have been observed in experiments with animal models. The studies with animals have also provided evidence that the dietary effects are exerted mainly at the promotional stage of carcinogenesis. Since breast and colon cancers account for a large proportion of cancer deaths in many countries, tumor-promoting effects of diet may be an important factor in overall cancer mortality.