Dietary Fat, Fatty Acids and Breast Cancer.

Results from some, but not all, epidemiological studies, and experimental investigations using animal models indicate that the level of fat in the diet, and more importantly the nature of the constituent fatty acids, influence both breast cancer risk and the progression of the established disease. High-fat diets rich in polyunsaturated omega-6 fatty acids stimulate mammary carcinogenesis and tumor progression; the long-chain omega-3 fatty acids present at high concentration in some fish oils exert inhibitory effects. Prominent among the biochemical mechanisms involved is the regulation of eicosanoid biosynthesis from dietary linoleic acid; both prostaglandins resulting from cyclooxygenase activity, and the leukotrienes and hydroxy-fatty acids produced under the influence of the lipoxygenases are involved in mammary carcinogenesis, tumor cell growth and apoptosis, angiogenesis, invasion and metastasis. A shift towards the typical high-fat Western diet, rich in omega-6 and poor in omega-3 fatty acids, may be a major factor in the increasing breast cancer incidence and mortality rates in Japanese women. Moreover, the results of the preclinical studies, together with supporting epidemiological data, suggest that a nutritional intervention comprising dietary omega-3 fatty acid supplementation and, in populations consuming a high fat diet a reduction in total fat and omega-6 fatty acid intake, may have a place not only in breast caner prevention, but as an adjunct to the surgical treatment of the breast cancer patient.