Introduction:
Although marine n-3 fatty acids are believed to be cardioprotective through their anti-arrhythmic, anti-thrombotic, anti-atherogenic and other effects, results from recent meta-analyses of marine n-3 fatty acids on cardiovascular disease (CVD) are controversial. We performed a meta-analysis of marine n-3 fatty acids on CVD outcomes in randomized clinical trials (RCTs) to test the hypothesis that marine n-3 fatty acids are anti-atherogenic. We also tested the hypothesis that such benefit is dose-dependent.
Methods:
A systematic review of English language articles using PubMed, EMBASE and Cochrane Library through Aug 2012 was performed selecting RCTs evaluating the effect of marine n-3 fatty acids intake for 2 years or more on cardiovascular diseases, coronary disease, arteriosclerosis, cardiac imaging techniques, and carotid artery ultrasound. Descriptive and quantitative information was extracted. Odds ratios were calculated for cardiac event outcome. Correlation coefficients were obtained from studies of which outcome is intima-media thickness (IMT) and coronary lumen diameter (CD). We converted the estimates into a single effect size; the log odds ratio and its corresponding standard error.
Results:
Of 14,236 citations retrieved, 13 studies were selected, including studies reporting IMT (n=3) and CD (n=2) and major CVD events (n=8). Overall, marine n-3 fatty acids significantly reduced atherosclerotic CVD (RR 0.94: 95%CI 0.90 to 0.99, p<0.05). There was no evidence of heterogeneity (p=0.65) or publication bias (p=0.37, Begg’s test). A sub-analysis among 8 studies of major CVD events showed the similar results (RR 0.94: 95% CI 0.89 to 0.99, p<0.05). Another sub-analysis among 4 studies excluding sudden cardiac death as an outcome showed RR of 0.91 (95% CI 0.82 to 1.02, p=0.097). A meta-regression analysis shows that dose of marine n-3 fatty acids was inversely associated with CVD outcome, although the association was not statistically significant (p=0.06).
Conclusions:
The result of our meta-analysis supports a modest anti-atherogenic effect of marine n-3 fatty acids. This benefit may be proportional to the amount of marine n-3 fatty acids consumed.
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