Meta-analysis contradicts popular belief about fish oil supplements

The $1 billion omega-3 fatty acids supplement industry took a surprise hit in April with the publication of a large meta-analysis that concluded the much-touted link between EPA/DHA supplements and heart health may be nothing more than a fish tale.

The study, published in the Archives of Internal Medicine, reviewed 14 trials involving 20,485 adults ages 40 to 80 with a history of heart disease. Half took fish oil pills; half took a placebo. Doses ranged from 0.4 to 4.8 grams daily for one to 4.7 years. In the end, supplementation “did not reduce the risk of overall cardiovascular events, all-cause mortality, sudden cardiac death, myocardial infarction, congestive heart failure or transient ischemic attack and stroke,” the authors wrote.

Their conclusion contradicts a wealth of studies that have swayed the American Heart Association to recommend heart disease patients use fish oil supplements and helped propel the category to begin rivaling multivitamins in popularity.

We asked coauthor Seung-Kwon Myung, MD, of the Center for Cancer Prevention and Detection in Ilsan, Korea, about the study.

Natural Foods Merchandiser: What prompted you to do the omega-3 analysis?

Seung-Kwon Myung, MD: Previous meta-analyses have reported that—contrary to our previous expectations—the use of vitamin or antioxidant supplements such as vitamin A, C, E, selenium and beta-carotene had no preventive effect and actually increased mortality. I was very interested in these findings. Because the consumption of omega-3s has increased globally in recent years, I wanted to know whether these supplements are beneficial.

NFM: You retrieved 1,007 articles from three databases and ended up with 14. How?

SKM: We included only randomized, double-blind, placebo-controlled trials that studied adult patients who had used omega-3 fatty acid supplements for at least one year. They also had to look at specific outcome measures such as angina, sudden cardiac death, all-cause mortality, congestive heart failure and stroke.

NFM: You omitted two large trials with positive results. Why?

SKM: The GISSI trial, which involved 11,324 heart attack survivors, indicated that the use of 1 gram per day of omega-3 fatty acid supplements over 3.5 years reduced the risks of death, and non-fatal heart attack and stroke. The JELIS trial of 18,645 Japanese participants with high cholesterol showed that supplementation with 1.8 grams per day of EPA lowered the incidence of major coronary events. However, these were open-label designs that did not use placebos, so they were not included. Participants who knew they were in the intervention group might have experienced placebo effects. Many physicians started prescribing omega-3 fatty acid supplements to heart patients based on the findings from these two trials. I believe we have to reconsider that recommendation.

NFM: These studies all included people who already had heart disease. Can omega-3s prevent heart disease in healthy people?

SKM: I wanted to answer that question, but unfortunately, there have been no trials looking only at healthy people. Not one.

NFM: What led us to believe omega-3s benefit the heart?

SKM: Evidence suggests that omega-3 fatty acids have anti-inflammatory, anti-atherogenic (plaque-formation preventing) and anti-arrhythmic (abnormal–heart–rhythm suppressing) effects. I don’t think those assumptions are wrong. But there is a big difference between taking omega-3s and eating fatty fish. I believe that omega-3 fatty acids may be most beneficial when eaten with other compounds found in fish. Meanwhile, supplements may contain synthetic chemicals.

NFM: Could omega-3 fatty acid supplements hurt you?

SKM: There is no evidence that there is harm in taking them. We have to wait for more trials on that issue.

NFM: What is the take-home message for consumers and retailers?

SKM: It is better to eat two servings per week of fish rich in omega-3 fatty acids. I do not recommend supplements for my patients.

Will consumers be swayed by the study? Experts say it's not likely.

Editor’s note: Additional editing for clarity and brevity occurred on this report because English is not the subject’s primary language.