Dietary Fat with Reference to the Spontaneous Appearance and Induction of Leukemia in Mice. ∗

Abstract

Diets high in fat have been reported to increase the rate of formation of certain types of induced tumors. 1 , 2 , 3 , 4 The total number of induced tumors was also increased when threshold amounts of carcinogen were used. 4 , 5 The induction of some types of tumors has been found, however, to be unaffected by the amount of fat in the diet. 2 , 4 , 5 , 6 The external presence of fat at the site of percutaneous application of carcinogen was considered to be at least partially responsible for the accelerating effect in the induction of skin tumors. 3 , 7 , 8 , 9 For spontaneous mammary cancer in virgin Dba mice, the total tumor incidence was greater and the time of appearance earlier if the animals were fed a diet containing 12 rather than 3% fat; 4 food intake of animals in both groups was approximately isocaloric, although the mice were fed ad libitum. Lavik and Baumann 9 positively correlated caloric intake with number of induced skin tumors when animals were fed relatively high and low fat diets. The high fat animals consumed 12 to 30% more calories and developed more tumors than mice on the low fat diet. Recently dietary coconut oil has been found to exert an inhibiting effect on the genesis of induced hepatic tumors of rats. 10

In the present experiments the effects of diets relatively high (32%) and low (3%) in fat were tested on (1) the appearance of spontaneous leukemia in the high leukemia F strain 11 and (2) the carcinogenic induction of leukemia in strain Dba.