Experimental evidence of dietary factors and hormone-dependent cancers.

Current awareness of the importance of environmental factors such as diet in the etiology of human cancer has stimulated renewed interest in animal models for studying effects of diet on tumorigenesis. Diet can influence cancer in animals by affecting the initiation or subsequent preneoplastic stage of tumorigenesis, but it has less effect on tumor growth. Caloric restriction has a general inhibitory influence on tumorigenesis. Dietary fat, on the other hand, tends to promote tumorigenesis, but only certain types of tumors, such as mammary tumors, are affected. Both caloric restriction and dietary fat appear to act primarily during the preneoplastic state, and their effects on hormone-dependent tumors may be mediated through changes in the hormonal environment. Variations in other dietary factors, such as protein, vitamins, or minerals, above the levels required for normal maintenance seem to have little influence on the genesis or growth of tumors.