Omega-3 fatty acids include the nutrients called docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).
The link between omega-3's and brain aging comes from a study published in Neurology, the medical journal of the American Academy of Neurology.
More: Supplement Your Knowledge of Omega Fats
"People with lower blood levels of omega-3 fatty acids had lower brain volumes that were equivalent to about two years of structural brain aging," said study author Zaldy S. Tan, MD, MPH, of the Easton Center for Alzheimer's Disease Research and the Division of Geriatrics, University of California at Los Angeles.
For the study, 1,575 people with an average age of 67 and free of dementia underwent MRI brain scans. They were also given tests that measured mental function, body mass and the omega-3 fatty acid levels in their red blood cells.
Read Omega-3's Protect the Brain
The researchers found that people whose DHA levels were among the bottom 25 percent of the participants had lower brain volume compared to people who had higher DHA levels.
Similarly, participants with levels of all omega-3 fatty acids in the bottom 25 percent also scored lower on tests of visual memory and executive function, such as problem solving and multi-tasking and abstract thinking.
Learn About Fish Oil Side Effects
Neurology, February 28, 2012 vol. 78 no. 9 658-664 "Red blood cell omega-3 fatty acid levels and markers of accelerated brain aging" Z.S. Tan, MD, MPH, et al. Department of Medicine, Division of Geriatric Medicine, and the Easton Center for Alzheimer's Disease Research (Z.S.T.), David Geffen School of Medicine at the University of California at Los Angeles.
The study was supported by the Framingham Heart Study's National Heart, Lung, and Blood Institute and the National Institute on Aging.