Milk cream does not enhance 2,7-dimethylbenz[a]anthracene-induced mammary tumorigenesis

We have previously reported that a diet enriched with butter showed an inhibitory effect on the development of mammary tumors in mice and rats. To solve the problem of whether the inhibitory effect of butter was caused by lipids of cow's milk, we have studied the effects of dried milk (WM), skim milk (SM) and milk cream (CR) on mammary tumorigenesis in rats. The lowest incidence of mammary tumors was observed in the CR group, although the difference from other groups was statistically not significant. However, the number of papillary carcinomas in the CR group was significantly lower than the WM group. The result indicates that milk lipids have no enhancing effect on mammary tumorigenesis.