Omega-3 fatty acids, long touted for their health benefits, may not prevent heart problems in people with no history of heart attacks, a new study in the New England Journal of Medicine finds. Although previous trials have found that omega-3 fatty acids offer benefits for people who have previously had a heart attack or heart failure, the case is different for patients with cardiovascular risk factors like high blood pressure or high cholesterol, but no previous heart problems. "Daily treatment with n-3 fatty acids did not reduce cardiovascular mortality and morbidity," the researchers wrote.

The team studied 12,513 patients, about half of which were given one gram daily of omega-3 fatty acids and the other half of which were given a placebo. After a median of five years of follow up, the rate of death, nonfatal heart attack, or nonfatal stroke was about the same in both groups: 11.7 percent of the patients in the fish oil group and 11.9 percent of the patients in the placebo group.

The study, which was conducted on an Italian population, shows that people already exposed to a healthy Mediterranean-style diet probably don't need to supplement that diet with fish oil unless they have a heart attack, lead author Maria Carla Roncaglioni told Reuters.

In the study, participants taking the fish oil did see certain factors like HDL cholesterol level improve slightly, Reuters adds. But other measures, like LDL cholesterol, blood pressure, and blood sugar remained similar to the group taking the placebo.

"Just giving a supplement on top of a non-heart-healthy lifestyle doesn't seem to help," American Heart Association spokeswoman and Tufts University professor Alice Lichtenstein told Reuters. "We thought vitamin E pills were going to be the answer and that turned out to be wrong. We though beta carotene as an antioxidant was going to reduce cardiovascular disease... and that pill didn't work. It's the whole package, not just popping one pill."