Omega-3 fatty acids have long been the darling of nutritional sciences, especially in the world of cardiovascular nutrition. When studies are published that state “no effect of omega-3s on heart disease,” there is a reasonable amount of confusion created. This is a problem with media reporting research in any field. In research, there are often many caveats (we studied this in a specific population, we gave this dose, the subjects were on these medications, etc.) that do not make it into the headline. It’s not without good reason – when you include all of the qualifiers surrounding the results of a study, the “headline” or the “bottomline” becomes wonky and meaningless to the lay public. Unfortunately, oversimplification of results can lead to some unintended consequences.
Jason Wu and Dariush Mozzafarian of the Harvard School of Public Health recently published an editorial in the journal Heart delving into the recent results from large omega-3 trials on cardiovascular disease outcomes. In this format, authors with an in-depth knowledge of this area can critically appraise the whole of the research and explain some of the more recent mixed findings. Here are some of the main points made in the paper:
- Omega-3s appear to prevent cardiovascular deaths but not necessarily events. Recent trials have not demonstrated that omega-3s have a protective effect on cardiovascular disease events. “Events” are not biomarkers, but actual disease effects such as a heart attack or stroke. Prospective cohort studies continue to show a consistent, significant benefit to eating more fish or omega-3 fatty acids and lower risk of cardiac death, not events.
- Observational data continues to support the role of omega-3s in improved cardiovascular health but these kinds of studies cannot prove causation. Seikikawa and colleagues recently published an observational study that compared the whole blood omega-3 levels (i.e. the Omega-3 Index) and coronary artery calcification in men from the USA and Japan. Men from Japan had omega-3 levels >100% higher than US men (9.1% vs. 3.8%, respectively) and had much lower rates of artery calcification. Adjusting the models for variables, such as age, blood pressure, lipids, etc. did not change the relationship, but including blood omega-3 fatty acid levels attenuated the relationship. It’s a positive study but still is an observational study in 2 very different populations with more differences than just omega-3 intake.
- A slightly higher baseline level of omega-3 fatty acids may be lessening the effect of supplementation. The greatest benefits are seen between 0 g EPA+DHA per day to 250 g – intakes above 250 mg/day do not seem to provide additional benefit for cardiac death. If the general public is getting a little bit more omega-3 daily due to fortified foods, supplementation or fish intake, the effect of adding 1 g omega-3s per day may be less pronounced.
- Assessing the effect of omega-3s on multiple cardiac endpoints, rather than just mortality, due to low event numbers makes finding significant effects more difficult. Many of the new, large randomized trials to report no effect of omega-3 fatty acids on cardiac endpoints (Alpha Omega, OMEGA, Origin, etc.). However, all the recent studies except for the Origin trial, were underpowered, meaning there were not enough cardiac deaths in their cohort during the time of the study to be able to see a statistically significant difference related to the treatment. Due to the low amount of endpoints achieved, often all kinds of heart disease endpoints are lumped into the analysis. This lack of specificity usually results in a null finding; omega-3s seem to have a stronger effect on cardiac mortality vs. cardiac events.
At the end of the day, the advice to include fatty fish rich in EPA+DHA is still prudent for cardiovascular and general health. As more research comes out, it is important to consider the context of single studies within the whole scope of the literature, rather than making health decisions based on headlines. Finding out your Omega-3 or Trans Fat Index or your 24 Fatty Acid Profile is one way to assess your health in a more objective manner in order to make more informed health decisions.
