Researchers have found that taking high doses of fish oil supplements — specifically one gram or more per day — may increase the risk of developing atrial fibrillation, an abnormal heart rhythm disturbance with potentially serious complications.
The new study was published in Circulation, the peer-reviewed journal of the American Heart Association and was conducted by researchers at the Smidt Heart Institute at Cedars-Sinai, according to a news release from the medical center.
Atrial fibrillation is the most common type of abnormal heart rhythm, causing the heart to contract irregularly and, sometimes, too quickly. It is estimated to affect 33 million people worldwide and can lead to blood clots, stroke, heart failure, and other heart-related complications.
According to the 2012 National Health Interview Survey, it is estimated that 7.8% of American adults, almost 19 million people, take fish oil supplements.
Recent research led by Christine M. Albert, MD, MPH, Professor of Cardiology and Chair of the Department of Cardiology in the Smidt Heart Institute, suggested neither vitamin D nor the omega-3 fatty acids found in fish oil prevent the development of atrial fibrillation. However, other clinical trials conducted outside of Cedars-Sinai pointed to an elevated risk of developing atrial fibrillation in patients treated with omega-3 fatty acids, causing confusion among clinicians and patients alike.
To further explore the potential reasons for differences between the results of these studies, Albert and team performed a meta-analysis, which combines the results of multiple scientific studies. This analytical comparison between studies suggested that the risk of developing atrial fibrillation is dependent on the dose of omega-3 fatty acids.
Although there's strong evidence that omega-3 fatty acids can significantly reduce blood triglyceride levels and arthritis pain, most experts agree it's best to get omega-3 fatty acids from eating fish several times a week.
In the current study, data was reviewed from 81,210 patients enrolled in seven clinical trials, including one conducted at Cedars-Sinai. The average age of patients enrolled in these trials was 65 and 39% were women. Out of these patients, 72.6% were in clinical trials testing less than or equal to one gram of omega-3 fatty acids per day and 27.4% were enrolled in clinical trials testing more than one gram of the supplement per day.
Patients who took more than one gram per day of omega-3 fatty acids had a 49% increased risk of developing atrial fibrillation, compared to just 12% of patients who took one gram or less of the supplement per day.