Is Omega-3 Index necessary for fish oil supplements for CVD risk prevention?

Abstract Several large prospective cohort studies demonstrated an association between higher cardiovascular disease (CVD) risk with low blood level of omega-3 fatty acids as well as low Omega-3 Index [<4% eicosapentaenoic acid (EPA)+ docosahexaenoic acid (DHA) to total fatty acids in red blood cell membrane]. However, randomized controlled trials of omega-3 fatty acids as either primary or secondary prevention have yielded controversial results. In this review, we summarize the evidence that supports or argues against the use omega-3 fatty acids, with a focus on the underlying mechanisms for the observed discrepancies (eg, differences in dosage, comparators and EPA levels or Omega-3 Index). Omega-3 Index is an independent risk factor for cardiovascular risk. The baseline Omega-3 Index can be used as a reference for whether and how much fish oil should be supplemented. To some degree, it can be used to explain why there are so much inconsistencies in clinical trials. Omega-3 Index could be a promising treatment target in clinical practice and in public health settings although there are still some barriers. This review summarizes current evidences from both epidemiological studies and randomized controlled trials of omega-3 fatty acids as primary and secondary prevention of CVD, and aims to provide a comprehensive overview of fish oil supplements on risk for CVD, and Omega-3 Index as a tool to identify subjects at high risk as well as a treatment target in CVD prevention.