New Review Supports Protective Effect of Marine Omega-3 Fatty Acids Against Breast Cancer
Zheng , J. S. et al., British Medical Journal, 346: in press , 2013
Dept. of Food Sci. and Nutrition, Zhejiang University, Hangzhou, China
The authors collected published articles and analyzed the data from numerous population studies wherein the association between the intake of long-chain omega-3 fatty acids as DHA(docosahexaenoic acid)/EPA(eicosapentaenoic acid) and DPA(docosapentaenoic acid) from marine sources was studied in relation to the risk of breast cancer. These studies combined involved 527,392 participants and 16,178 breast cancer events. Overall, the intake of marine omega-3 fatty acids was significantly associated with a 14 % reduction in the risk of breast cancer. An inverse relation between DHA and EPA intakes and risk was found while no significant association appeared for DPA. Furthermore, no significant relationship between the dietary intake of the short-chain omega-3 fatty acid as LNA (alpha-linolenic acid) and breast cancer was found. The apparent protective effect of the marine-derived omega-3 fatty acids against breast cancer was similar whether dietary intakes were assessed or omega-3 status in the body was measured as bio-markers (such as circulating blood levels of DHA/EPA). The authors estimated that the risk of breast cancer was reduced by 5 % overall for 0.1 grams (100 mg) of marine omega-3 fatty acid(s) daily.
Dr. Holub's Comments:
Various studies using cell culture systems and animal models have led to a number of biological mechanisms which may contribute to the any protective effects of DHA/EPA against breast cancer. The long-chain omega-3 fatty acids are known to inhibit the formation of ‘eicosanoids’ from cellular arachidonic acid (omega-6 fatty acid) which promote cell proliferation and tumor growth. DHA is metabolized to bio-active products known as ‘resolvins’ which possess beneficial anti-inflammatory properties. DHA/EPA have the potential to suppress estrogen production and estrogen-stimulated tumorigenesis. It is noted that, in the present review, the authors present a graph (Fig. 6) showing a progressive reduction in the relative risk of breast cancer with increasing intakes of marine omega-3 fatty acids up to 0.7 % of energy/day. Assuming a daily intake of approx. 2200 Calories/day, such an intake would be the equivalent of 1710 mg of DHA/EPA per day (or about 12-fold current intakes in North America).