Omega-3s and the Heart: Which Patients Are Most Likely to Benefit?

JoAnn E. Manson, MD, DrPH


July 10, 2017

Hello. This is Dr JoAnn Manson, professor of medicine at Harvard Medical School and Brigham and Women's Hospital. I would like to talk with you about the marine omega-3 fatty acids, EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid), fish oil, and heart health.

There have been wide swings of the pendulum in terms of conclusions of meta-analyses[1,2,3,4] and clinical guidelines[5,6,7,8] about the role of fish oil supplements in prevention of cardiovascular disease (CVD) over recent years. A couple of months ago, the American Heart Association published a science advisory in Circulation. Here are a few clarifications and caveats about these guidelines.

First, these guidelines do not relate directly to dietary fish. There is a clear recommendation to encourage about two servings of fish per week in the diet, preferably dark, fatty fish. Whether the benefits for CVD are due directly to the omega-3 fatty acids or from replacing red meat or other less helpful components of the diet is not known.

The rating group of the science advisory wisely focused on randomized clinical trials of fish oil supplements in the prevention of clinical events. They concluded that there are two groups most likely to benefit: those with recent myocardial infarction or known history of coronary heart disease, and those with known reduced ejection fraction heart failure.

The committee also concluded that there are several groups in whom fish oil supplements are not indicated and patients are not likely to benefit. These include patients without known CVD but who have diabetes or prediabetes, patients with multiple risk factors for CVD but no prior clinical events, patients with atrial fibrillation, and patients post-op from cardiac surgery. The committee was unable to make any recommendation for primary prevention because of the absence of data in large-scale, randomized clinical trials for primary prevention.

These guidelines are very reasonable. With these high-risk populations, even a 10% reduction in coronary death in those who already have a history of coronary disease, or 8%-9% reduction in hospitalization or mortality in those with heart failure, would be a major clinical benefit compared with the very small risk for side effects or adverse events with the low dose of fish oil supplementation.

It is important to keep in mind that the trials tending to show the greatest benefits were open-label trials and trials done a while ago that were not conducted in the setting of maximal medical therapy. In a setting with high-dose statins, aspirin, beta-blockers, and angiotensin-converting enzyme inhibitors, trials have generally shown only a very modest benefit of fish oil supplements. Again, the benefits are likely to outweigh the risks for the high-risk groups that were identified.

Stay tuned for trials in primary prevention. The vitamin D/omega-3 trial, (VITAL), which is being directed by our research group, is studying omega-3 fatty acids in close to 26,000 participants for prevention of CVD and cancer. Those results should be available in spring 2018. Other large-scale, randomized trials are ongoing and should have results within 1-2 years.

This is a good example of where shared decision-making with a patient can be very helpful. Some patients will not want to add fish oil capsules to their current complex medical regimen. Others would be more than happy to do so. In fact, about 8% of the population is already taking fish oil supplements.

Thanks so much for your attention. This is JoAnn Manson.


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