This study looked at the effects of red blood cells (RBC) levels of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on brain structure and function in 1575 middle-aged to elderly adults free of clinical dementia. The results found that participants with the lowest levels of RBC DHA had lower total brain and greater white matter hyperintensity volumes. Participants with lower DHA and omega-3 index (RBC DHA+EPA) levels also had lower scores on tests of visual memory, executive function, and abstract thinking. The authors conclude "we found that lower levels of RBC DHA and EPA in late middle age were associated with markers of accelerated structural and cognitive aging".
Tan ZS, Harris WS, Beiser AS, Au R, Himali JJ, Debette S, Pikula A, Decarli C, Wolf PA, Vasan RS, Robins SJ, Seshadri S. Red blood cell omega-3 fatty acid levels and markers of accelerated brain aging. Neurology. 2012 Feb 28;78(9):658-64.