Fish Oil No Help for Secondary CVD Prevention

Omega-3 fatty acid supplements failed to show a benefit for secondary prevention of cardiovascular disease (CVD), authors of a meta-analysis concluded.

Data from 14 randomized trials showed a relative risk of 0.99 for patients treated with omega-3 supplements, virtually identical to the risk in the placebo groups.

A small reduction in cardiovascular death disappeared after exclusion of a trial that had major methodologic problems, investigators reported online in Archives of Internal Medicine.

"Our results show insufficient evidence of a secondary preventive effect of omega-3 fatty acid supplements against overall cardiovascular events among patients with a history of cardiovascular disease," Seung-Kwon Myung, MD, of the National Cancer Center in Ilsan, South Korea, and co-authors concluded in their article.

The findings are at odds with analyses performed before 2010, which showed a significant benefit for secondary prevention, the authors added.

However, the results are consistent with those of the most recent clinical trials, which generally have shown no effect of omega-3 supplements for prevention of cardiovascular events in patients with existing CVD.

A series of articles published in the 1970s made a case for consumption of fish or marine mammals rich in omega-3 fatty acids as the explanation for the low prevalence of CVD among Eskimos living in Greenland.

Subsequent clinical and preclinical investigations supported the epidemiologic evidence by suggesting that omega-3 fatty acids have anti-inflammatory, anti-atherogenic, and anti-arrhythmic effects, the authors wrote in their introduction.

Continued research yielded inconsistent or conflicting results about the effects of omega-3 fatty acids on cardiovascular risk. A systematic review and meta-analysis showed an overall benefit of omega-3 intake on primary and secondary cardiovascular prevention (Am J Clin Nutr 2006; 84: 5-17).

Data from randomized trials, most of which focused on secondary prevention, have remained controversial, owing to inconsistent results and methodologic problems of some studies, the authors continued. Moreover, no meta-analyses have included results of clinical trials published since 2010.

Myung and colleagues performed a comprehensive review and meta-analysis that incorporated the most recent data on the effects of omega-3 supplementation on secondary cardiovascular prevention.

From 1,007 published articles reviewed, they selected 14 randomized, double-blind, placebo-controlled trials for the analysis. The trials involved a total of 20,485 patients with a history of CVD. In all of the trials, patients used omega-3 supplements for at least a year.

The primary analysis focused on the association between omega-3 fatty acid supplementation and total cardiovascular events.