Taking supplements of omega-3 fatty acids doesn't seem to reduce a person's risk of heart disease, a new study finds.
The findings are part of a study that was primarily designed to examine the effects of omega-3 supplements and some vitamins on vision health. About 4,200 people ages 50 to 85 with the age-related eye problem macular degeneration participated in the study. Some of the participants were randomly asked to take omega-3 supplements or the eye vitamins lutein and zeaxanthin, while others were given a placebo.
By the end of the five-year study, about 450 participants had suffered a cardiovascular problem, such as heart attack or stroke. Researchers found no benefit among individuals who had taken omega-3 or eye vitamins; they were as likely to have experienced a heart problem during the study period as people who took a placebo, according to the study published today (March 17) in the journal JAMA Internal Medicine. [Top 10 Amazing Facts About Your Heart]
The findings add to "a growing body of evidence from clinical trials that have found little cardiovascular benefit from moderate levels of dietary supplementation," the researchers wrote in the journal article.
Omega-3 fatty acids, which can be found in oily fish and are also available in a supplement form, have been the subject of investigation after some studies suggested they could protect a person's cardiovascular system.
However, the findings have been inconsistent. Some diet studies have found people who eat fish regularly had a lower risk of heart disease, whereas other clinical studies failed to find a beneficial link between omega-3 intake and heart disease risk.
Nevertheless, omega-3 supplements have sold more than $25 billion in 2011, and their market is estimated to grow 15 percent each year, according to market research studies. These supplements are increasingly used for prevention of cardiovascular disease, either with a doctor's prescription or as over-the-counter products, said Dr. Evangelos Rizos from University Hospital of Ioannina, Greece, in an editorial published along with the study.
Many years of research has failed to find conclusive evidence for the benefits of omega-3 supplementation, and doctors should inform their patients about the uncertainty surrounding the benefits of taking omega-3 supplements, Rizos said.
The study only looked at omega-3 intake from supplements and not from fish. There's some evidence that eating seafood rich in omega-3 fatty acids has health benefits, so the National Institutes of Health suggests such foods be part of a heart-healthy diet.
As omega-3 fatty acids can reduce triglycerides, a type of fat found in the blood, the supplements should be considered only for people who have severely high triglyceride levels, who are an extreme minority in the population, Rizos said. Similarly, the Food and Drug Administration has approved omega-3 supplementation only for people with this condition.
The new study also found that lutein and zeaxanthin, antioxidants found in green leafy vegetables, didn't have an effect on heart disease risk, despite previous suggestions that these vitamins may lower the risk of heart problems, the researchers said.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.