Re: Breast Cancer Risk in Rats Fed a Diet High in n-6 Polyunsaturated Fatty Acids During Pregnancy

Extract

Hilakivi-Clarke et al. ( 1 ) reported that consumption of a diet high in corn oil (50% linoleic acid) during pregnancy increases the risk in rats of developing carcinogen-induced mammary tumors, possibly by increasing pregnancy levels of circulating estrogens. Because of the relevance to human breast cancer, the conclusions of this study are of considerable interest to those involved in the study of nutritional carcinogenesis. However, two aspects of this article concern the reader. First, the diet itself, although isocaloric, differs significantly, not only with regard to total fat but also to total fiber. In fact, there is a fourfold difference in fiber intake between animals fed the high-fat versus low-fat diets. This is not a minor difference, particularly in light of our recent article on the role of fiber in carcinogen-induced rat mammary cancer ( 2 ) . Since fiber, even a simple fiber such as purified cellulose, can alter the enterohepatic recirculation of estrogens, it may play a key role in the effects noted. Second, tumor incidence is extremely low, not to mention the total tumor number, suggesting a methodologic problem with either 7,12-dimethylbenz[ a ]anthracene administration or purity.