High-dose fish oil can increase the likelihood of A-fib in heart patients

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By Amy Norton
HealthDay reporter

MONDAY, May 3, 2021 (HealthDay News) – Many people take fish oil to protect their hearts, but a new study suggests that prescription versions may increase the risk of common heart rhythm problems.

It’s all about prescription omega-3 fatty acids that are naturally found in fish oil. The drugs are often prescribed to people with very high levels of triglycerides, a type of blood fat that has been linked to an increased risk of heart attack and stroke.

According to the American Heart Association, prescription omega-3 fatty acids can lower triglycerides by 20 to 30% in most people.

But the drugs are also controversial because their ultimate benefits for the heart are unclear.

Now the new study – an analysis of five past clinical trials – suggests caution is warranted. Overall, study patients who received omega-3 fatty acids developed a risk of developing atrial fibrillation (a-fib) more than a third higher than those who received placebo. Doses of fish oil ingested ranged from 0.84 grams to 4 grams per day.

A-fib is a common heart rhythm disorder, or arrhythmia, in which the upper chambers of the heart begin to shake chaotically instead of effectively contracting.

A-fib isn’t immediately life-threatening, but it’s also “not benign,” said Dave Dixon, a researcher on the study and associate professor at Virginia Commonwealth University (VCU) in Richmond.

Over time, Dixon said, a-fib can lead to complications like heart failure or stroke.

How exactly prescription omega-3s could contribute to a-fib is unclear, according to Dixon.

However, the increased risk was pretty consistent across studies – more consistent than the heart benefit, in fact, said co-researcher Salvatore Carbone, assistant professor at VCU.

In all five studies, there were more a-fib cases in omega-3 patients than in placebo patients, although the risk difference was not statistically significant in all studies.

However, when the researchers pooled the results of all five studies, there was a clear result: omega-3 patients were 37% more likely to develop A-fib than placebo patients.

In contrast, only one study showed that an omega-3 product could lower the risk of other heart diseases.

In this study, called REDUCE-IT, patients using a product called Vascepa (icosapentethyl) saw their risk of “cardiovascular events” by 25%. These included heart attacks, strokes, and death from cardiovascular causes.

But even in this study, the risk of a-fib in omega-3 users increased by 35%.

Why has only one study found benefits for the heart? It’s not clear here either, said Dixon.

However, Vascepa is different from the fish oil products that were tested in the other studies. It only contains one omega-3 called EPA, while the other products contain a combination of EPA and DHA.

And in the REDUCE-IT study, Dixon said, higher levels of EPA in the patients’ blood correlated with lower cardiovascular risk.

This suggests that focusing on EPA could be “the way forward”. But the conflicting results on the benefits of omega-3 fatty acids – along with the potential risk of a-fib – underscore the need for further study, the researchers said.

The analysis was published on April 29 in the European Heart Journal – Cardiovascular Pharmacotherapy.

Findings on the benefits of fish oil for the heart have indeed been “inconsistent,” said Linda Van Horn, a member of the Heart Association’s nutrition committee and professor at Northwestern University’s Feinberg School of Medicine in Chicago.

And that includes low-dose, over-the-counter fish oil supplements.

“There is limited and inconsistent data on the benefits or risks of taking fish oil supplements,” said Van Horn.

Therefore, the Heart Association recommends eating two servings of fish a week instead. Van Horn said oily fish like salmon, trout, albacore tuna, and herring are the best sources of omega-3 fatty acids.

Prescription omega-3 fatty acids were tested in the studies of the current analysis. But Carbone said he would be wary of over-the-counter fish oil supplements as well.

“We don’t know if over-the-counter products could have the same effects,” he said.

Over-the-counter fish oil is considered a dietary supplement, so it is not regulated by the U.S. Food and Drug Administration as it would be a drug, Dixon said.

Both he and Carbone said it was best to speak to a doctor or pharmacist before starting any fish oil product – and that people on prescription omega-3 fatty acids should speak to their doctor before stopping.

More information

Harvard Medical School has more about fish oil and heart health.

SOURCES: Salvatore Carbone, PhD, Assistant Professor, Kinesiology and Health Sciences, Virginia Commonwealth University, Richmond, Virginia; Dave L. Dixon, PharmD, Associate Professor, Outpatient Care and Vice Chairman, Clinical Services, Department of Pharmacotherapy and Outcomes Science, Virginia Commonwealth University, Richmond, Virginia; Linda Van Horn, PhD, RD, Professor and Director of Nutrition, Department of Preventive Medicine, Feinberg School of Medicine, Northwestern University, Chicago, and member of the Nutrition Committee, American Heart Association, Dallas; European Heart Journal – Cardiovascular Pharmacotherapy, April 29, 2021, online

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