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Nov. 15, 2010 (Chicago) -- Prescription supplements of omega-3 fatty acids do not appear to prevent recurrences of atrial fibrillation, a type of irregular heartbeat that can lead to stroke, researchers report.
"We now have definitive evidence that fish oil did not work for most patients with atrial fibrillation," says Peter R. Kowey, MD, head of cardiology at the Main Line Health Hospital outside Philadelphia.
Kowey presented the findings here at the American Heart Association's annual meeting. They were simultaneously published online by the Journal of the American Medical Association.
More than 2 million Americans have atrial fibrillation, or AF, a condition characterized by irregular heart rhythms. Many people with atrial fibrillation are more likely to have a stroke because their weakened heartbeats allow blood to pool in an upper chamber of the heart. Pooled blood is more likely to form clots, which can travel to the brain and block blood flow, causing a stroke.
Eating oily fish such as salmon and albacore tuna that are rich in omega-3 fatty acids has been shown to be good for heart health, and some people take them for atrial fibrillation.
Smaller studies looking at supplements in people with atrial fibrillation have had conflicting results.
So Kowey and colleagues decided to put a pure prescription formulation of omega-3 to rigorous scientific testing. They studied 663 people, 542 of whom had paroxysmal atrial fibrillation, characterized by occasional irregular heartbeats that start and stop suddenly. The rest had persistent atrial fibrillation, marked by longer ongoing episodes.
Participants were given either a placebo or 8 grams of omega-3 supplements daily for seven days, followed by 4 grams a day for the remaining 23 weeks of the trial.
The prescription supplements are sold under the brand name Lovaza. They’re made by GlaxoSmithKline, which funded the trial.
Over the 24 weeks of the study, 46% of people taking placebo and 52% of people taking omega-3 supplements had atrial fibrillation recurrences.
"There was no significant difference in recurrence rates in people with persistent or paroxysmal AF," Kowey tells WebMD.
A total of 5% of people taking placebo and 4% of people receiving the omega-3 capsules stopped taking the drugs because of side effects, the most common of which were diarrhea and nausea.
Over-the-counter fish oil supplements are even less likely to help people with atrial fibrillation, Kowey says.
"People are spending an enormous amount of money on stuff that doesn't work," he says.
"This is data that we've needed sorely," says Christine Albert, MD, of Brigham and Women's Hospital in Boston. "A lot of people are taking these supplements… they showed no evidence of any benefit."
Mariell Jessup, MD, medical director of the Penn Heart and Vascular Center at the University of Pennsylvania, tells WebMD that the best way to get your omega fatty acids is to eat two to three servings of fish a week.
There is still a possibility that the supplements may work in combination with certain arrhythmia drugs in atrial fibrillation or for other heart conditions, Kowey says.
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