BOSTON, MASSACHUSETTS. Evidence for the benefits of omega-3 fatty acids in maintaining cardiovascular health has been mounting since the 1970s. Nevertheless, a recent working group convened by the US National Institutes of Health concluded that a definitive trial is needed. Towards the aim of resolving current controversies over the benefits of n-3 FAs on cardiovascular health, a team of researchers from the Tufts-New England Medical Center undertook a systematic review of studies on n-3 FAs consumed as fish or fish oils rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) or as alpha-linolenic acid (ALA).
They selected 15 studies on secondary prevention and 33 on primary prevention of cardiovascular disease, each lasting for a minimum of one year. Most of the studies on secondary prevention found that fish oil significantly reduced all-cause mortality, heart attack, cardiac and sudden death, and stroke. For primary prevention, most studies found fish consumption was linked with lower rates of all-cause mortality and cardiac events, but the evidence for stroke prevention was less strong. The benefits of ALA consumption for reducing cardiovascular risk were not convincing. The researchers believe these results support the importance of an adequate intake of n-3 FAs, either through fish or supplements or both, for reducing the risk of all-cause mortality, cardiac and sudden death, and possibly stroke. They add that the benefits are clearer for secondary prevention, and that very few adverse effects were seen.
In an editorial, experts from Columbia University point out that questions remain over the optimum n-3 to n-6 FA ratio, the best surrogate measure of n-3 FA levels, and the relative benefits of EPA and DHA. The biological pathways of the preventive effects of n-3 FAs on cardiovascular health must also be better explained, as must the crucial periods in the lifespan for adequate n-3 FA intakes. They conclude by asking whether intake recommendations for EPA and DHA can now be set, and refer to the American Heart Association guidelines - an intake of about 1 gram of EPA and DHA per day for patients with cardiovascular disease, and about half that (equaling 2 servings of oily fish per week) for those without. Public health initiatives are needed to increase EPA and DHA intakes, they write.
Wang, C. et al. n-3 Fatty acids from fish or fish-oil supplements, but not alpha-linolenic acid, benefit cardiovascular disease outcomes in primary- and secondary-prevention studies: a systematic review. The American Journal of Clinical Nutrition, Vol. 84, July 1, 2006, pp. 5-17
Deckelbaum, R. J. and Akabas, S. R. n-3 Fatty acids and cardiovascular disease: navigating toward recommendations. The American Journal of Clinical Nutrition, Vol. 84, July 1, 2006, pp. 1-2