RCT-based recommendations on use of fish oil supplementation for CVD prevention

A scientific statement issued in 2002 by the American Heart Association (AHA), concluded, based on 2 large RCTs that supplementation with eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) (omega-3 polyunsaturated fatty acids (PUFA), commonly called fish oils) significantly reduced fatal cardiac events. Based on the evidence, the AHA recommended that patients with documented coronary heart disease (CHD) consume ~1 g/d EPA+DHA, preferably from oily fish, but supplements may be considered in consultation with a physician.

Since then, multiple RCTs have assessed the effects of supplementation with EPA+DHA provided as prescription medications, supplements or enriched margarine on the occurrence of clinical cardiovascular diseases. The current Science Advisory document is an update of the 2002 scientific statement, that focuses on large RCTs of supplementation with major clinical CVD endpoints. Evidence from meta-analyses of RCTs were considered in secondary instance. Observational data and posthoc findings were not considered.

Based on evidence from RCTs assessing the role of supplementation in secondary prevention among patients with diabetes mellitus and prediabetes, patients at high risk of CVD, and those with prevalent CHD, recommendations are provided. The advice focusses on the effects of omega-3 PUFA (referring to omega-3 PUFA, EPA and DHA) supplementation. Studies of dietary intake of omega-3 PUFAs are not considered.

The advisory discusses the features of available RCTs and provides the rationale for the recommendations. Existing AHA criteria are used to indicate the strength of the recommendation and the level of evidence.

Based on review of the cumulative evidence, prior recommendations for patients with prevalent CHD are updated. CHD death may be reduced by omega-3 PUFA supplements among patients with prior CHD, but treatment does not reduce the incidence of recurrent nonfatal MI. The majority of co-authors concluded that omega-3 PUFA supplementation is reasonable for secondary prevention of CHD death, but a minority would have preferred a slightly lower strength of recommendation than the class IIa recommendation given for this indication.

No proven benefit of omega-3 PUFA supplementation has been described to reduce the risk of stroke (incident nor recurrent). The effect on primary prevention of heart failure or atrial fibrillation has not been evaluated in an RCT, but omega-3 PUFA might have a benefit in HFrEF patients, while evidence does not support supplementation to prevent recurrent AF, nor after cardiac surgery.

Moreover, when data are available, recommendations are offered for patients with other clinical indications, including patients with diabetes mellitus and prediabetes.

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