Calorie consumption level influences development of C3H/Ou breast adenocarcinoma with indifference to calorie source

To analyze simultaneously the influence attributable to calorie consumption level and percentage of dietary fat on the spontaneous development of mammary adenocarcinoma, virgin female C3H/Ou mice were separated into five dietary groups. Four groups of mice were fed purified diets either ad libitum (16-18 kcal/mouse/day) or restricted 40% in calorie consumption (10-11 kcal/mouse/day), and diets contained either 4.5%, 7.5%, 67%, or 68% calories from fat. Mice that consumed isocaloric diets developed breast malignancy at a comparable pace. Consuming a diet in which fats were present only at levels sufficient to satisfy the threshold requirement of essential fatty acids, 4.5-7.5% of the total calories, or alternatively where dietary fat represented greater than 67% of the total calories consumed, did not significantly alter the tendency for breast tumor development. The pace and frequency with which tumors occurred reflected the host's level of calorie consumption. Mice consuming a high caloric diet, low or high in fat, tended to have a shortened latency to breast tumor formation, an increased incidence of breast tumors, elevated serum prolactin levels, elevated levels of antibodies to mouse mammary tumor virus, and elevated circulating immune complex levels.