Unlike other supplements, fish oil has been thoroughly studied, says Joan Munson, a professor at Harvard Medical School. But the results have been mixed, and researchers and doctors are still debating whether fish oil is good for heart health. It's also been found that taking fish oil slightly increases the risk of developing atrial fibrillation, a type of irregular heartbeat.
The evidence is now here regarding both the benefits and risks of fish oil.
Extensive research, but benefits unknown
After reading the report from Greenland, researchers began looking at people in other parts of the world, and in study after study, they found that people who ate fish at least once a week were less likely to die from coronary heart disease than those who rarely ate fish. Animal studies have found that fish oil helps keep electrical signals in heart cells working properly, said cardiologist Dariush Mozaffarian, director of the Food and Medicine Institute at Tufts University.
“These findings have had a huge impact,” said Dr. Christine Albert, chief of cardiology at Cedars-Sinai Medical Center in Los Angeles, adding that it's reasonable to hope that taking fish oil in supplement form might have a similar effect.
However, most clinical trials of fish oil capsules have not reported a reduction in deaths from heart disease or overall cardiovascular events such as heart attacks and strokes. That was the finding of a 2018 meta-analysis that combined the results of 10 omega-3 trials involving nearly 78,000 people. Similarly, in a 2018 study that followed more than 15,000 adults with type 2 diabetes for an average of seven years, a 2019 study that followed more than 25,000 adults over 50 for an average of five years, and a 2020 study that tested high-dose omega-3s in more than 13,000 people at risk for cardiovascular disease, researchers reported no benefit of omega-3s on overall heart health.
“Study after study has proven that there's simply no effect,” said Dr. Steven Nissen, a cardiologist at the Cleveland Clinic who led the 2020 trial. (One study published in 2018 showed significant benefits from high doses of the omega-3 fatty acid EPA, but it was widely criticized for using mineral oil as a placebo, which may increase the risk of heart disease, Dr. Nissen said.)
