Omega-3 polyunsaturated fatty acids in rodent models of breast cancer.

Quantitative increases in certain dietary fats promote mammary tumor growth, but the experimental data indicate that this tumor promoting capability is not equally expressed by all fatty acid families. There is a large body of evidence from experiments using either carcinogen-induced or transplanted animal mammary tumor models, as well as in vitro studies, which demonstrates that the omega-6 polyunsaturated fatty acids (PUFA) promote mammary tumor development more effectively than omega-3 PUFA. These data indicate that increases in the dietary levels of omega-6 PUFA enhance tumor development, while equivalent increases in dietary levels of omega-3 PUFA often delay or reduce tumor development. Several theoretical mechanisms have been proposed for these contrasting results, but as yet, no definitive explanation has been universally accepted.