Modification of spontaneous mammary tumors in mice fed different sources of protein, fat and carbohydrate.

The effects of different sources of dietary protein (milk, soy, wheat, fish and beef), fat (corn oil and butter), and carbohydrate (dextrin and sucrose) on the development of spontaneous mammary tumors in virgin female C3H/HeJ mice were investigated. Weanling mice were randomly divided (28 mice/group) and fed ad libitum one of 14 equicaloric diets containing either 11% or 33% protein and 5% or 30% fat or a standard mouse feed for approximately 2 years. Beginning at 6 months of age, tumor incidence, non-specific deaths, individual weights and amount of food consumed were monitored. Variations in tumor incidence were most pronounced when the mice fed different sources of protein (at a high level) were compared. The mice fed the low fat diets containing either low milk protein (high carbohydrate) or high fish protein generally exhibited the lowest tumor incidence and highest percent survival. High weight gain was correlated with early tumor appearance, but not with tumor incidence later in the experiment. The mice fed a low fat diet containing low milk protein were tumor-free significantly longer than mice fed the diets containing fish or beef. The only groups with 100% tumor incidence by 120 weeks of age were those fed diets containing sucrose (table sugar) or a high fat level.