Is fish oil useful or harmful to the heart?

Unlike most other supplements, fish oil has been thoroughly studied, says Dr. JoAnn Manson, a professor of medicine at Harvard Medical School. But the results of those studies have been mixed, leaving researchers and doctors still debating whether fish oil is good for heart health. They’ve also revealed that taking fish oil is linked to a slightly higher risk of developing atrial fibrillation, a type of irregular heartbeat.

Here’s where the evidence for both the benefits and risks of fish oil stands today.

Lots of studies, but unclear benefits

After reading the reports from Greenland, researchers began looking at people elsewhere in the world and discovered, study after studythat those who ate fish at least once a week were less likely to die from coronary heart disease than those who rarely ate fish. In animal testingthey found that fish oil kept electrical signals in heart cells functioning properly, said Dr. Dariush Mozaffarian, a cardiologist and director of the Food is Medicine Institute at Tufts University.

“There was a lot of excitement” about the findings, said Dr. Christine Albert, chair of cardiology at Cedars-Sinai Medical Center in Los Angeles. And it was natural to hope that people could get the same benefits from taking fish oil in supplement form, she added.

But most clinical trials of fish oil capsules have not reported a reduction in deaths from heart disease or in the overall number of cardiovascular events such as heart attack and stroke, A Meta-analysis from 2018 a combination of the results of 10 omega-3 studies in which almost 78,000 people participated. Similarly, researchers reported no overall heart health benefits of omega-3 fatty acids Process 2018 of more than 15,000 adults with type 2 diabetes who were followed for an average of seven years; in a Trial 2019 of more than 25,000 adults aged 50 and over who were followed for an average of five years; and in a Trial 2020 of a high dose of omega-3 fatty acids tested in more than 13,000 people at risk of cardiovascular disease.

“One study after another showed absolutely no benefit,” said Dr. Steven Nissen, a cardiologist at the Cleveland Clinic, who led the 2020 trial. (A test, published in 2018showed a striking benefit from a high dose of the omega-3 EPA. But it has been widely criticized for its use of mineral oil, which increase the risk of heart disease(like the placebo, Dr. Nissen said.)