Middle-aged people with high levels of the beneficial omega-3 fat DHA in their blood did significantly better on memory and reasoning tests in a 2010 study published by The Journal of Nutrition. The most common food sources you can use to boost your DHA is oily fish like salmon and mackerel.

Authors M.F. Muldoon, C.M. Ryan, L. Sheu, J.K. Yao, S.M. Conklin, S.B. Manuck
Institution Departments of Geriatrics, Neurology, Pharmacology & Toxicology, and Epidemiology, University of Arkansas for Medical Sciences
Publication Name Journal of Nutrition
Publication Date April 2010

Existing evidence links greater dietary intake of fish and (n-3) PUFA to better early brain development and lowered risk of cognitive disorders in late life. The mechanisms for these associations remain unclear and may be related to specific (n-3) fatty acids and may concern cognitive function generally rather than only early brain development and age-related cognitive dysfunction. In this investigation, we tested potential associations between (n-3) fatty acids in serum phospholipids and major dimensions of cognitive functioning in mid-life adults. Participants were 280 community volunteers between 35 and 54 y of age, free of major neuropsychiatric disorders, and not taking fish oil supplements. Dietary biomarkers were alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenonic acid (DHA) in serum phospholipids measured using GC. Five major dimensions of cognitive functioning were assessed with a 75-min battery of neuropsychological tests. In covariate adjusted regression models, higher DHA (mol %) was related to better performance on tests of nonverbal reasoning and mental flexibility, working memory, and vocabulary (P <or= 0.05). These associations were generally linear. Associations between DHA and nonverbal reasoning and working memory persisted with additional adjustment for participant education and vocabulary scores (P <or= 0.05). Neither EPA nor ALA was notably related to any of the 5 tested dimensions of cognitive performance. Among the 3 key (n-3) PUFA, only DHA is associated with major aspects of cognitive performance in nonpatient adults <55 y old. These findings suggest that DHA is related to brain health throughout the lifespan and may have implications for clinical trials of neuropsychiatric disorders.