A very revealing and encouraging recent study showed that older adults who had higher levels of omega-3 fats on blood tests lived longer. Those with lower levels had a higher incidence of earlier deaths from heart disease. The surprise in this study was that DHA was the fatty acid associated with less heart mortality, not EPA.
The Cardiovascular Health Study looked at the effect of omega-3 fat levels in 2,500 older adults during the period 1992-2008. Those with the highest versus lowest levels of omega-3 fats had a 27 percent reduced incidence of mortality from all causes. And the findings could even predict that a higher level of omega-3 fats resulted in an additional 2.2 years of life for these two groups after age 65.
The take home lesson from this study is that you should take a balanced fish oil supplement that contains plenty of DHA in addition to EPA.
Mozaffarian D, Lemaitre RN, King IB, Song X, Huang H, Sacks FM, Rimm EB, Wang M, Siscovick DS. Plasma Phospholipid Long-Chain ω-3 Fatty Acids and Total and Cause-Specific Mortality in Older Adults: A Cohort Study. Ann Intern Med. 2013 Apr 2;158(7):515-25.