Certain effects of dietary fats on the production of liver tumors in rats fed p-dimethylaminoazobenzene.

Hydrogenated coconut oil and its component fatty acids appear to be the most striking examples of dietary lipid inhibitors reported for the carcinogen p-dimethylaminoazobenzene. When these substances were fed to rats as the sole sources of lipid in synthetic diets containing the azo dye very few liver tumors, if any, appeared by 6 months (3, 4). If," however, a fat such as corn oil was fed instead an incidence of 60 to 80 per cent at 6 months was obtained. The effects of other fats on the carcinogenicity of p-dimethylaminoazobenzene has been the subject of two recent papers. Gy6rgy and his associates (1) have stated that Crisco and butter fat were cocarcinogenic as compared to lard when these fats were fed at high levels with diets low in protein, but no supporting data were offered. Opie (6) has compared diets containing various levels of Crisco, and has concluded that high levels of fat increase the rate of formation of liver tumors. The dye was fed continuously in these experiments and the animals that lived the longest (those on high fat) consumed more carcinogen than those that died early (those on low fat). This report deals with the effects of the kind and the level of certain fats in the diet on the carcinogenicity of p-dimethylaminoazobenzene in rats fed a synthetic diet. Corn oil was compared with olive oil at a level of 5 per cent in the diet and corn oil, lard, and Crisco were tested at a level of 20 per cent. The series included also a diet free of added fat.