Prescribed omega-3 fatty acids are treated, which are found naturally in fish oil. Medications are usually prescribed to people with very high levels triglycerides, a type of blood fat related to an increased risk of suffering heart attack i stroke.
According to the American Heart Association, prescription omega-3s can reduce triglycerides by as much as 20% to 30% in most people.
But drugs are also controversial, because their ultimate benefits to the heart are unclear.
Now the new study – an analysis of five pasts clinical trials – suggests caution. Overall, patients tested with omega-3 were more than a third more likely to develop atrial fibrillation (a-fib) than those who received a placebo. Doses of fish oil taken ranged from 0.84 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 tremble chaotically instead of contracting effectively.
A-fib does not immediately endanger life, but neither is it “benign,” said Dave Dixon, one of the study’s researchers and an associate professor at Virginia Commonwealth University (VCU) in Richmond.
Over time, Dixon said, afib-fib can cause complications such as heart attack a stroke.
According to Dixon, it is unclear exactly how prescription omega-3s could contribute to fiber.
However, the increased risk was fairly consistent across all trials; in fact, it was more consistent than the heart benefits, said co-researcher Salvatore Carbone, an assistant professor at VCU.
In all five trials, there were more cases of aerial fibrillation among omega-3 patients than placebo patients, although the difference in risk was not statistically significant in all studies.
But when the researchers pooled the results of the five trials, there was a clear result: patients with Omega-3 were 37% more likely to develop fibrillary fibrosis than patients with placebo.
In contrast, only one trial showed that an omega-3 product could reduce the risks of other heart conditions.
In that trial, called REDUCE-IT, patients using a product called Vascepa (icosapent ethyl) saw their risk of cardiovascular events drop by 25%. This included heart attack, stroke and death from cardiovascular causes.
Even in this study, however, the risk of fibrosis increased by 35% among omega-3 users.
Why has only one trial found cardiac benefits? Again, it’s still unclear, Dixon said.
But, he added, Vascepa is different from the fish oil products tested in the other trials. It only contains one omega-3, called EPA, while the other products contain a combination of EPA and DHA.
And in the REDUCE-IT trial, Dixon said, higher levels of EPA in patients’ blood correlated with lower cardiovascular risks.
This hints, he said, that focusing on the EPA could be “the way forward.” But conflicting findings about the benefits of omega-3s, along with the potential risk of fibro-fibrillates, highlight the need for more studies, the researchers said.
The analysis was published on April 29 at European Heart Journal – Cardiovascular Pharmacotherapy.
Linda Van Horn, a cardiac association nutrition committee member and professor at Northwestern University Feinberg School of Medicine in Chicago, said the findings on the heart benefits of fish oil have been “inconsistent.”
And that includes over-the-counter low-dose fish oil supplements.
“There is limited and inconsistent data on the benefit or risk of taking fish oil supplements,” Van Horn said.
So the cardiac association recommends eating two servings of fish a week. Van Horn said fatty fish, such as salmon, trout, bluefin tuna and herring, are the best sources of omega-3s.
Trials in the current analysis tested prescription omega-3s. But Carbone said he would also be cautious with over-the-counter fish oil supplements.
“We don’t know if over-the-counter products could have these 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 Dixon pointed out.
Both he and Carbone said it is best to talk to a doctor or pharmacist before starting any product with fish oil. – and that people on an omega-3 prescription should talk to their doctor before stopping.
Harvard Medical School has more advantages fish oil and heart health.
SOURCES: Salvatore Carbone, PhD, Assistant Professor of Kinesiology and Health Sciences, Virginia Commonwealth University, Richmond, Va .; Dave L. Dixon, Pharmacist, Associate Professor of Outpatient Care and Vice President, Clinical Services, Department of Pharmacotherapy and Outcome Science, Virginia Commonwealth University, Richmond, Va .; Linda Van Horn, PhD, RD, professor and head, nutrition division, department of preventive medicine, Northwestern University Feinberg School of Medicine, Chicago, and member of the Nutrition Committee, American Heart Association, Dallas; European Heart Journal – Cardiovascular Pharmacotherapy, April 29, 2021, online