Omega-3 fatty acids supplementation on major cardiovascular outcomes: an umbrella review of meta-analyses of observational studies and randomized controlled trials

OBJECTIVE: Omega-3 fatty acids are commonly used as a lipid-lowering agent or dietary supplement for the purpose of prevention of cardiovascular diseases. However, even large-scale clinical trials have not shown significant results demonstrating clear clinical benefits in cardiovascular diseases. Thus, this umbrella review aims to summarize and evaluate the evidence of clinical effects of omega-3 fatty acids supplementation on cardiovascular outcomes through comprehensive analyses of previous randomized controlled trials (RCTs) or observational cohort studies. MATERIALS AND METHODS: We conducted relevant publication search in PubMed, Embase, and Cochrane Database of Systematic Reviews. We retrieved and analyzed 3,298 articles published until August 28th, 2019. RESULTS: We identified 29 relevant articles and analyzed 83 meta-analyses of RCTs or cohort studies therefrom. As a result, we identified 12 cardiovascular outcomes that are related to omega-3 fatty acids supplementation. Among them, total mortality from major cardiovascular causes (RR 0.92, 95% CI 0.86 to 0.98) had significant inverse associations, and moreover, statistical significances were maintained even in subgroup analysis of large-scale RCTs including more than 1,000 patients (RR 0.94, 95% CI 0.88 to 0.99). CONCLUSIONS: Our umbrella review study shows that omega-3 fatty acids supplementation have a clinical benefit in reducing mortality from cardiovascular causes. However, many studies still have shown conflicting results, and therefore, further studies will be needed to verify the clinical benefit of omega-3 supplementation.