Diet and Hepatic Tumor Formation*t

Hepatic tumors readily appear in rats fed a basal ration of carrots and polished rice to which butteryellow (N,N-dimethyl-p-aminoazobenzene) has been added in oil ( i2 , I6), and tumor incidence can be markedly reduced when liver or yeast is added to such a ration at a IO to 15 per cent level (16, 17) or when the basal ration is wheat (I3, 2o). Nutri t ionally the rice-carrot diet is grossly deficient in several dietary essentials such as protein, salts, and various members of the vitamin B complex. However, neither the addition of fish protein, nor salts, nor the known members of the vitamin B complex alone or in combination, prevented the formation of liver tumors ( i6 ) . Recently the combination of high riboflavin and high casein has been reported to inhibit hepatoma formation on a diet of rice and carrot (1 i ) . Our studies concern the effects of numerous modifications in the basal diet on the rate of tumor formation with butter-yellow. Semisynthetic diets adequate for growth and maintenance were employed and particular emphasis placed on the relative effectiveness of various proteins. Certain substances known to be present in liver and yeast were also assayed for protective potency. In the course of these investigations a laparatomy technic for the detection of early liver tumors was perfected.