African-Americans benefited regardless of fish intake, showing a 77 percent lower risk of heart attack. “This could be a chance finding,” said Dr. JoAnn Manson, a director of the study and the chief of the Division of Preventive Medicine at Brigham and Women’s Hospital. “We do plan to pursue it in greater detail and try to replicate it in a separate trial because if this can be reproduced, that would be a very dramatic benefit to African-Americans.”

Because there is still more research to be done, experts don’t necessarily recommended that African-Americans take omega-3.

If you have some history of heart disease or high triglycerides ( an estimated 25 percent of adults in the United States do, according to data from the National Health and Nutrition Examination Survey in 2015 ), it may be a good idea to take omega-3.

The potential downside, because supplements are not regulated, is that production isn’t standardized so we don’t know what’s in them, according to Dr. Pieter Cohen, of Cambridge Health Alliance, who is an associate professor of medicine at Harvard Medical School.

He said that supplements are expensive and that money could alternatively be spent on a healthier diet. As an internist, Dr. Cohen has seen negative behavioral effects in some of his patients who take supplements.

“I have many patients who are like, ‘I’ll take my supplement and then I won’t worry about eating healthfully during the day,’” Dr. Cohen said. “That’s really misguided. Because in this case we have absolutely no evidence that replacing a healthy meal of fish with an omega-3 supplement is better.”