Although omega-3 fatty acids have well documented properties which would reduce the cardiovascular (CV) disease risk, the evidence from randomized controlled trials (RCTs) remains inconclusive. We performed a meta-analysis of the available RCTs for investigating the CV preventive effect of administrating at least 1 gram/day, and for at least 1 year, omega-3 fatty acid supplements to patients with existing CV disease.

RCTs published up to March 2013 were searched from PubMed, EMBASE, and the Cochrane Library. Two of us independently reviewed and selected eligible trials.

Of 360 articles retrieved, 11 randomized, double-blind, placebo controlled trials fulfilling inclusion criteria, overall involving 15,348 patients with a history of CV disease, were considered in the final analyses. No statistically significant association was observed for all-cause mortality (RR, 0.89; 95% CI, 0.78 to 1.02) and stroke (RR, 1.31; 95% CI, 0.90 to 1.90). Conversely, statistically significant protective effects were observed for cardiac death (RR, 0.68; 95% CI, 0.56 to 0.83), sudden death (RR, 0.67; 95% CI, 0.52 to 0.87), and myocardial infarction (RR, 0.75; 95% CI, 0.63 to 0.88).

Overall, our results supply evidence that long-term effect of high dose omega-3 fatty acid supplementation may be beneficial for the onset of cardiac death, sudden death and myocardial infarction among patients with a history of cardiovascular disease.