Indications for omega-3 fatty acid supplementation in prevention of cardiovascular disease: From fish to pharmaceuticals.

OBJECTIVE: To explore the evidence for omega-3 fatty acid (O3FA) supplementation in primary and secondary prevention of cardiovascular disease (CVD).

SOURCES OF INFORMATION: PubMed, Cochrane reviews, and Google Scholar were searched for meta-analyses and reviews related to O3FAs and CVD. Salient, recent randomized controlled trials referenced in these reviews were retrieved. Current lipid guidelines were reviewed.

MAIN MESSAGE: Most O3FAs are derived from marine or aquatic microalgae, which are consumed by fish. The essential fatty acids eicosapentaenoic acid and docosahexaenoic acid are mainly sourced from fish, with a small fraction coming from plants. Omega-3 fatty acids modestly lower triglyceride levels, but the major impact on CVD is through a variety of other mechanisms related to cell membrane function, antioxidant properties, and reduction of atherogenic small low-density lipoprotein cholesterol particles. Guidelines continue to recommend eating 2 servings of fish per week. There is little evidence of benefit of O3FAs in primary prevention of CVD. Given that 40% of Canadians have insufficient levels and that these low levels may be associated with other chronic diseases over time, supplementation with O3FAs could be considered, particularly in those with hypertriglyceridemia, in those who eat no fish, or for vegetarians or vegans. Doses up to 1 g daily are considered safe. For secondary prevention after statin optimization, if triglyceride levels are between 1.5 and 5.6 mmol/L, guidelines recommend with level 1A evidence taking 2 g of icosapent ethyl twice a day. This is also recommended in primary prevention for patients with diabetes and hypertriglyceridemia and additional CVD risk factors. As fish stocks dwindle over time, preserving fisheries for developing countries and obtaining O3FA from microalgal or genetically modified plant sources may become important.

CONCLUSION: All guidelines recommend at least 2 servings of oily fish per week, although benefit from O3FAs is mostly seen in secondary prevention. Fish oil and combination preparations of eicosapentaenoic acid and docosahexaenoic acid have failed to show benefit at any dose at any level of prevention in patients who are appropriately prescribed statins. High-dose eicosapentaenoic acid shows substantial benefit in selected patients taking statins who have high triglyceride levels.