Effect of dietary fat and cholesterol on dimethylbenz[a]-anthracene-induced mammary tumorigenesis in Sprague-Dawley rats.

The effect of dietary fats and cholesterol on dimethylbenz[a]-anthracene-induced mammary tumorigenesis was studied in female Sprague-Dawley rats. When the dietary fat source (at the 5% level) was palm oil (saturated fat) or corn oil (unsaturated fat), dietary cholesterol at the 0.2% level increased the tumor number of rats fed corn oil, but not those fed palm oil. Perilla oil (rich in alpha-linolenic acid) reduced tumor development as compared with safflower oil (rich in linoleic acid), but again dietary cholesterol at the 0.5% level diminished the favorable effect of n-3 polyunsaturated fatty acid (PUFA). The adverse effect of cholesterol was also observed in the n-6 PUFA fat. The promotive effect of dietary cholesterol was not necessarily associated with the change in the production of prostaglandin E2 by the tumor tissue or in the immunopotentiation. These results at least stress that the contrasting effects of dietary fats should be carefully evaluated whether cholesterol is present simultaneously or not.