Some research has suggested that the omega-3 fatty acids in fish oil can help prevent an irregular heart beat called atrial fibrillation. However, a new study finds these supplements have little effect on the condition once it develops.
Atrial fibrillation is a common heart problem usually kept under control with medications and sometimes with surgical procedures. The primary danger from the condition is the risk of a stroke from a clot caused by the irregular heart beat, the researchers explained.
"There is no role of omega-3 fatty acids for the prevention of atrial fibrillation in patients with previous atrial fibrillation," said lead researcher Dr. Alejandro Macchia, from the GESICA Foundation in Buenos Aires, Argentina. "However, these results did not rule out the possibility that these agents may have a role in the primary prevention of atrial fibrillation."
The report was published Dec. 19 in the Journal of the American College of Cardiology.
One expert agreed that the finding seems to further discount the use of fish oil supplements for atrial fibrillation.
"Atrial fibrillation in the most common arrhythmia in adults, and impacts millions of men and women in the United States," said Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles. "Atrial fibrillation results in substantial morbidity, mortality and health care expenditures."
Many anti-arrhythmic medications have limited efficacy and undesirable side effects, Fonarow said. "It has been hoped that omega-3 fatty acids [fish oil] supplementation would have anti-arrhythmic effects and some clinical trials have suggested this may be case," he added.
"However, on the basis of this as well as other recent clinical trials, omega-3 fatty acid supplementation, while safe, does not appear to provide any clinically relevant benefits as an anti-arrhythmic agent," Fonarow said.
For the study, Macchia's team randomly assigned more than 500 patients with atrial fibrillation to receive fish oil supplements or placebo.
Over a year, the researchers looked for recurrent episodes of atrial fibrillation.
During that time, there was no significant difference in the number of episodes of atrial fibrillation between the groups, the researchers found.
During the year, 24 percent of those taking the supplements had episodes of atrial fibrillation, while only 19 percent of those receiving the placebo had such episodes.
There were also no differences between the groups in deaths, stroke, heart attacks or heart failure, the researchers noted.
"If you are taking omega-3 fatty acids for any other reason such as secondary prevention after a heart attack, heart failure or high levels of triglycerides, you should continue to take these compounds," Macchia noted. "However, there is no need to begin taking fish oil if the objective is to prevent recurrent atrial fibrillation."
Another expert, Dr. Neil Sanghvi, a clinical electrophysiologist at Lenox Hill Hospital, in New York City, said that "it is not understood how omega-3 may prevent atrial fibrillation. Quite frankly, I am not sure the effect is powerful enough to prevent atrial fibrillation."
If patients are taking these supplements, they should continue to take them since there are no apparent adverse effects, he added.
"But they shouldn't take it with the expectation that it's going to reduce atrial fibrillation," Sanghvi noted.