Lipids and carcinogenesis.

Experiments with animals and epidemiological data on human populations have provided evidence that high fat diets increase the incidence of certain types of cancer, such as breast cancer and colon cancer. High fat diets enhance mammary tumorigenesis in rats only when the fat contains a certain minimal level of essential fatty acids. Dietary fat appears to act as a promoter rather than affecting initiation of mammary tumors. It may do this by producing a more favorable environment for development and growth of tumor cells, either by changing the hormonal environment, by altering the properties of cell membranes thorugh changes in their lipid composition, or by other mechanisms, such as alterations in immune responses to tumor cells. The effect of dietary fat on colon cancer may be related to increased production and excretion of bile acids, some of which have been shown to be promoters of intestinal cancer in animals. It may be possible to utilize this knowledge of the effects of dietary fat on carcionogenesis to develop new methods for prevention and treatment of breast and colon cancer.