Here we go again. Another study that attempts to show omega-3 fish oil supplements are not beneficial for heart health has been published in the major medical journal New England Journal of Medicine. The study appears to be sound from the outside: double-blind, placebo-controlled clinical trial with over 12,000 participants followed over five years. But when we take a closer look, however, we see that there are some major flaws that question the conclusion drawn from the study, “Our findings provide no evidence of the usefulness of omega-3 fatty acids for preventing cardiovascular death or disease in this population.” Headlines read, “Omega-3 Fails to Prevent Heart Attacks,” “Fish Oil Supplements May Not Prevent Heart Trouble,” and “Study Questions Omega-3 Benefits.”
The study involved over 12,000 participants with multiple cardiovascular risk factors who received either 1 gram of fish oil daily containing 850 mg of EPA and DHA (the two fatty acids most known for heart health benefits) or placebo. Similar to previous studies that claimed omega-3 supplementation was not beneficial for heart health, the dosage used in this study is low. Could it be that participants did not get enough fish oil? It certainly could.
But the plot thickens. The placebo used in the study consisted of a softgel filled with olive oil. What do we know about olive oil? It’s beneficial for heart health. The olive oil may have exerted some benefits of its own, making it more difficult to detect a beneficial effect of fish oil over olive oil. Yet another factor that calls the results into question is the fact that the study was done in Italy. What diet do Italians eat? I would think many eat a Mediterranean diet (which includes plenty of olive oil), well known to be beneficial for heart health.
Could these factors have contributed to the unexpected lower rates of death from heart-related events found in both placebo and omega-3 groups? They sure could. In fact, this finding led to a revision of the study protocol that changed the primary endpoint of the study, or the main measure they were taking to determine efficacy of the omega-3 treatment. Instead of looking at cumulative death rate, nonfatal heart attack rate, and nonfatal stroke rate, instead they looked at the time between cardiovascular events and eventual death or hospitalization. When they did this, they were unable to find—not surprisingly—a difference between the group receiving the omega-3 supplement and the group receiving olive oil placebo.
I also want to add, as I have in the past, that it is crucial to measure the Omega-3 Index, or the level of omega-3 fatty acids in red blood cell membranes, as a way to know that the omega-3s are being taken by participants and being absorbed and incorporated into the body’s tissues. The researchers failed to take this measure, so we cannot know if participants received enough omega-3.
Before you have second thoughts about taking omega-3 fish oil, make sure you know the whole story. Studies like these are greatly misleading, despite their prominence. I don’t buy it, and neither should you.
- M.C. Roncaglioni, et al., “n-3 fatty acids in patients with multiple cardiovascular risk factors.” N Engl J Med. 2013 May 9;368(19):1800-8.