Summation and new approaches to diet and cancer.

Epidemiological studies have shown a relationship between several types of human cancer, such as esophageal, breast, and colon, and particular kinds of diet, indicating the presence of carcinogenic factors in those diets. Observations in animals have shown that some types of cancer in them are related to certain carcinogens in their food. Several types of cancer similar to that in humans have been induced in experimental animals by administration of carcinogens, such as nitrosamines and mycotoxins, suggesting that their presence in human diets can increase cancer risk. The search for such carcinogens, and for others presently unsuspected in human diets, should be continued with the objective of reducing or eliminating human exposure to them. The role of promoting agents, such as fats, in colon and breast cancer needs to be further investigated, and exposure to them should be reduced. Two sources of carcinogens that need increased study are the formation of carcinogens in cooking, especially of fats and proteins, and the endogenous formation of carcinogens in the gastrointestinal tract, e.g., N-nitroso compounds.