In 1970, two Danish researchers traveled to Greenland to investigate a nutritional paradox: The Inuit people living in the region consumed foods very high in fat, yet reportedly had very low rates of heart attacks.
That observation flew in the face of nutrition dogma at the time, which held that eating fatty foods — like whale and seal meat and oily fish — would clog your arteries and cause heart disease.
The Inuit on Greenland, a Danish territory, had lower levels of blood cholesterol and triglycerides than people back in Denmark, the researchers reported. The reason, they hypothesized, was that the Inuit diet was rich in omega-3 fatty acids — particularly EPA and DHA, which are concentrated in fish and the animals that eat them.
These findings sparked decades of scientific and commercial interest in the role omega-3 fatty acids play in heart health, even after later studies suggested that, in fact, the Inuit had rates of heart disease similar to those found in Europe, the United States and Canada. Today, omega-3 supplements are among the most popular in the United States, surpassed only by multivitamins and vitamin D. Among U.S. adults 60 and older, about 22 percent reported taking omega-3s in a 2017-2018 survey.
Unlike most other supplements, fish oil has been rigorously studied, said 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 beneficial for heart health. They have also revealed that taking fish oil is linked to a slightly greater 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.
A boatload of studies, but unclear benefits
After reading the dispatches from Greenland, researchers began looking at people elsewhere in the world and finding, in study after study, that those who consumed fish at least once per week were less likely to die from coronary heart disease than those who rarely ate fish. In animal experiments, they found that fish oil helped keep electrical signaling in heart cells functioning properly, said Dr. Dariush Mozaffarian, a cardiologist and director of the Food is Medicine Institute at Tufts University.
