There have been mixed findings about the benefits of DHA (an omega-3 fatty acid), but in a study involving 485 older adults (55+) with age-related cognitive impairment, those randomly assigned to take DHA for six months improved the score on a visuospatial learning and episodic memory test. Higher levels of DHA in the blood correlated with better scores on the paired associate learning task. DHA supplementation was also associated with better verbal recognition, but not better working memory or executive function.
Other research has found no benefit from DHA to those already with Alzheimer’s, although those with Alzheimer’s tend to have lower levels of DHA in the blood. These findings reinforce the idea that the benefit of many proactive lifestyle strategies, such as diet and exercise, may depend mainly on their use before systems deteriorate.
The daily dose of algal DHA was 900 mg. The study took place at 19 clinical sites in the U.S., and those involved had an MMSE score greater than 26.
 . Beneficial effects of docosahexaenoic acid on cognition in age-related cognitive decline. Alzheimer's and Dementia [Internet]. 2010 ;6(6):456 - 464. Available from: http://www.alzheimersanddementia.com/article/S1552-5260(10)00040-3/abstract