One of my first experiments as a young researcher was to compare how different fatty acids were processed. After feeding 3 different types of fatty acids to human cells, an “Aha Moment!” was experienced. While 2 of the fatty acids were processed in a similar manner, the 3rd behaved very differently. Astonished by these results, I repeated the experiment only to arrive at the same conclusion. Compared to palmitate (a saturated fatty acid found in animal-based products) and oleate (a monounsaturated fatty acid found in olive oil), the omega-3 fatty acid, EPA (found in oily fish) was minimally processed into triglycerides. These experiments published nearly 3 decades ago among others, identified some of the mechanisms by which marine-derived omega-3 fatty acids (primarily EPA and DHA), reduce triglyceride levels.
Because high triglycerides increase cardiovascular risk, studies have been designed to examine whether lowering triglycerides reduces risk. While results of one of these major trials will not be forthcoming for another 1-2 years, several others have now been completed. Two of these trials used pure EPA and both demonstrated improvement in cardiovascular risk. The landmark REDUCE-IT trial found that the pure EPA formulation, Icosapent Ethyl, reduced risk by 25% while a prior trial that tested purified EPA in a Japanese population, known as the JELIS trial lowered risk by nearly 20%.
By contrast, 2 trials, STRENGTH and OMEMI, were reported and simultaneously published this past week at the Annual Scientific Sessions of the American Heart Association. Both showed that the combination of EPA and DHA did not favorably influence heart-related risk compared to the placebo group. It is important to point out that these 2 studies build upon the results of prior clinical trials that also failed to show benefit when EPA and DHA were combined.
So why is EPA effective for the heart whereas DHA is not? Even though both lower triglycerides, EPA exhibits a number of cardioprotective properties/effects whereas DHA appears to oppose some of these beneficial effects as elegantly demonstrated in a series of experiments spearheaded by my colleague, Dr. Preston Mason.
Bottom Line: EPA found in herring/salmon/sablefish (among others) and in purified form (Icosapent Ethyl) is the omega-3 fatty acid proven for heart health…and that is no fish tale!
Michael Miller, M.D., is Professor of Cardiovascular Medicine, Epidemiology and Public Health at the University of Maryland School of Medicine in Baltimore, Maryland, USA.