A new study confirms that fish oil supplements can increase the risk of common cardiac arrhythmias – especially when doses are above 1 gram per day.
It is about drugs and food supplements with omega-3 fatty acids, which occur naturally in fish oil.
Fish is considered a generally heart-healthy food, but some studies have linked omega-3s in capsule form to an increased risk of atrial fibrillation or a-fib.
With a-fib, instead of effectively contracting, the upper chambers of the heart shake chaotically. It’s not immediately life-threatening, but over time it can lead to complications such as heart failure or stroke.
But while some studies have found an increased risk of a-fib in omega-3 users, others don’t, said Dr. Christine Albert, Professor of Cardiology at Cedars-Sinai Medical Center in Los Angeles.
So she and her colleagues conducted a meta-analysis and summarized the results of seven previous clinical studies testing omega-3 drugs and dietary supplements.
“With a meta-analysis you can see if there are effects that were not discovered in a single study,” said Albert.
The analysis – recently published in the journal Circulation – included a total of over 81,000 patients. During the study period, 3.6% developed a-fib.
Overall, Albert and her team found that study participants who received omega-3 were more likely to develop a-fib than those who received a placebo over an average of five years.
And the dose played a role: Patients taking more than 1 gram per day had a 49% higher risk of a-fib than placebo users. In contrast, the risk was only increased by 12% in patients taking 1 gram or less per day.
Prescription omega-3s – brands like Vascepa and Lovaza – are often prescribed to people with very high triglycerides, a type of blood fat that has been linked to an increased risk of heart attack and stroke.
Vascepa has also been shown to reduce the risk of heart attack and stroke when taken with a cholesterol-lowering statin. However, this does not apply to any other omega-3 medication or over-the-counter dietary supplement.
Albert said that people who have been prescribed omega-3s shouldn’t stop taking it on their own, but rather talk to their doctor about the risk of a-fib if they haven’t already.
“I don’t want to scare anyone,” said Albert.
At the same time, she added, people should be aware of the possibility of developing a-fib while taking omega-3 – and the possible symptoms, such as a fast, fluttering heartbeat and dizziness.
People with possible symptoms should let their doctor know, Albert said – although a-fib can also be symptom-free and can only be discovered at a doctor’s appointment.
As for over-the-counter supplements, Albert suggested speaking to her doctor again. Although they are marketed as dietary supplements, they cannot be assumed to be completely safe. In addition, there is no evidence of a cardiac benefit.
“Think of it as if you were taking medication and talk to your doctor about whether it is right for you,” Albert said.
For its part, the American Heart Association encourages people to get omega-3s from fish.
“Fish is an excellent source of omega-3s, as well as protein and many other important nutrients,” said Linda Van Horn, a member of the AHA’s Nutrition Committee.
Specifically, people should aim for two weekly servings of oily fish like salmon, trout, or albacore tuna, said Van Horn, who is also a professor of nutrition at Northwestern University’s Feinberg School of Medicine in Chicago.
“Fish oil supplements are not the same and should be discussed with your doctor,” she said.
It’s unclear why taking omega-3s might increase A-fib risk, although a prescription drug appears to lower the risk of heart attack and stroke. But a-fib, a problem with the heart’s electrical activity, is different from heart attack and stroke – which are usually caused by blockages in the arteries.
And it’s plausible, Albert said, that omega-3 affects the risks of these diseases differently.
Harvard Medical School has more about fish oil and heart health.