Omega-3 and omega-6 polyunsaturated fatty acids and metabolic syndrome: A systematic review and meta-analysis

Background & aims Previous studies suggest that polyunsaturated fatty acids (PUFAs) may reduce the risk of metabolic diseases, but some have shown ambiguous results. The aim of this study was to systematically evaluate and summarize available evidence on the association between omega-3 and omega-6 PUFA levels and risk of metabolic syndrome (MetS). Methods A systematic literature search of articles published until December 2017 was conducted in PubMed, Web of Science, and Cochrane Library databases. Meta-analyses of the highest vs. lowest categories of omega-3 and omega-6 PUFAs were conducted using the random effects models. Results Thirteen studies (2 case-control, 9 cross-sectional, 1 nested case-control, and 1 prospective cohort) with 36,542 individuals were included. Higher omega-3 PUFA levels in diets or blood were associated with a 26% reduction in the risk of MetS (odds ratio (OR)/relative risk (RR) 0.74, 95% confidence interval (CI) 0.62–0.89). This inverse association was evident among studies with Asian populations (OR/RR 0.69, 95% CI 0.54–0.87), but not among those with American/European populations (OR/RR 0.84, 95% CI 0.55–1.28). Null results were found regarding the association between circulating/dietary omega-6 PUFAs and MetS. Conclusion The present meta-analysis indicates that higher intakes of omega-3 PUFAs, but not omega-6 PUFAs, was associated with lower MetS risk; adding to the current body of evidence on the metabolic health effects of circulating/dietary omega-3 PUFAs.