Fish oil supplements of so-called omega-3 fatty acids, found in oily fish like tuna and salmon, may not do much to ward off heart attacks and strokes in people who already have heart disease, according to an international analysis.
The research, which appeared in the Archives of Internal Medicine and covered 14 studies, found that there was no difference in the number of heart attacks, strokes or deaths among more than 20,000 people with heart disease who were randomly assigned to take either fish oil supplement or fish oil free placebo pills. Research has been mixed on the possible heart-related benefits of the omega-3 fatty acids, specifically those known as EPA and DHA, which can be taken as fish oil supplements as well as eaten. Places such as the American Heart Association recommend at least two servings of such fish a week.
"There is a common perception that fish oil supplements have been proven to prevent cardiovascular disease, and in fact the evidence has been inconsistent and inconclusive," said JoAnn Manson, head of preventive medicine at Brigham and Women's Hospital in Boston, who co-wrote a commentary published with the study.
"It's an important issue, because a large percentage of the population is taking fish oil supplements over-the-counter," she told Reuters Health.
Researchers from Korea combined the results of 14 studies that tracked heart disease patients taking fish oil or a placebo, without knowing which they were getting, for between one and five years. That included reports from the United States and India, as well as Italy, Germany and elsewhere in Europe.
Those who were assigned to take the fish oil supplements were just as likely to have a range of heart-related emergencies, or to die, as study participants taking placebos containing vegetable oil or other substances not associated with heart health.