The stimulating effect of dietary fat on carcinogenesis.

Abstract

1. The relationship of dietary fat to the incidence of carcinomas induced in mice with carcinogenic hydrocarbons was investigated. Synthetic type diets were fed in which caloric intake was varied by removing glucose from the ration and the level of fat was increased from 2 per cent to 27 per cent or to 61 per cent by isocaloric substitution for glucose. 2. The diet containing 61 per cent fat and no carbohydrate stimulated carcinogenesis about the same as diets containing 27 per cent fat. This suggested that dietary fat per se does not promote the formation of skin carcinomas induced with benzpyrene. 3. When the tumor promoting action of diets containing 2 per cent and 27 per cent fat were compared at two calorie levels it was shown that the greater net energy value of the higher fat diet was sufficient to account for all of the stimulating effect of the 27 per cent fat diet on tumor formation. 4. For a true appraisal of the effect of the three major dietary components on the induction of tumors, the diets should be fed on the basis of an equal net energy value rather than isocaloric allowances calculated from the gross caloric values of the dietary components. 5. Mice that were fed a diet containing 61 per cent of fat and no carbohydrate for 254 days gained weight and appeared normal.