Richmond, VA—Pharmacists might want to caution about use of omega-3 supplements in some patients.

A study published in European Heart Journal—Cardiovascular Pharmacotherapy, a journal of the European Society of Cardiology, reports that omega-3 supplements are associated with an increased likelihood of developing atrial fibrillation (AF) in people with high blood lipids.

“Currently, fish oil supplements are indicated for patients with elevated plasma triglycerides to reduce cardiovascular risk,” said study author Salvatore Carbone, PhD, of Virginia Commonwealth University, “Due to the high prevalence of elevated triglycerides in the population, they can be commonly prescribed. Of note, low dose omega-3 fatty acids are available over the counter, without the need for a prescription.”

Past studies were unclear on the risk, so researchers performed a meta-analysis of five randomized controlled trials investigating the effects of omega-3 fatty acid (O3FA) supplementation on cardiovascular outcomes. Participants had elevated triglycerides and were either at high risk for cardiovascular disease or had established cardiovascular disease.

In the studies, 50,277 patients received fish oils or placebo and were followed up for between 2 and 7.4 years. The dose of fish oils varied from 0.84 g to 4 g per day.

O3FA supplementation was associated with a significantly increased risk for AF compared with placebo with an incidence rate ratio of 1.37 (95% CI, 1.22-1.54; P <.001, the researchers point out.

“Although one clinical trial indicated beneficial cardiovascular effects of supplementation, the risk for atrial fibrillation should be considered when such agents are prescribed or purchased over the counter, especially in individuals susceptible to developing the heart rhythm disorder,” Dr. Carbone added.

Background information in the report states that the “mechanisms through which O3FA supplementation may increase the risk for AF remain largely unknown, clearly highlighting the need for more mechanistic clinical trials to investigate such effects. In fact, O3FA have been previously shown to stabilize the cardiac membrane resulting in protective effects against arrhythmias, including ventricular arrhythmias.”

The study advises that some previous studies reported a higher postoperative AF in patients with elevated O3FA levels. “Of note, dedicated studies investigating the effects of O3FA supplementation on ventricular arrhythmias, and in targeted high-risk populations (e.g., post-myocardial infarction patients) remain to be determined and further study is encouraged,” the authors write.

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