One of the reasons nutrition experts recommend eating fish twice a week is that they are a good source of docosahexaenoic acid (DHA), an omega-3 fat that has heart-healthy benefits. (For vegans, there are plant-source (microalgae-based) DHA supplements available.) Now preliminary studies suggest that DHA may help boost brain power too. It makes sense: DHA comprises much of the cell membranes in our brains. And food producers are taking the concept and running with it–they’re adding DHA to foods like yogurt, soy milk and eggs, then marketing them with “smart” slogans. But do these products really maximize mental performance?

Supporting evidence: Some research links higher intakes of DHA with reduced risk of Alzheimer’s disease and the cognitive decline that precedes it. In a 2003 study in the Archives of Neurology, people aged 65-plus who ate at least one (DHA-rich) fish meal per week had a 60 percent reduced risk for Alzheimer’s. And growing evidence suggests DHA supplementation during pregnancy and early infancy may result in superior cognitive performance of the child. This past June, a randomized clinical trial in the American Journal of Clinical Nutrition revealed that 9-month-old babies of mothers who’d eaten DHA-fortified cereal bars (about 200 mg of DHA daily) during the last trimester of their pregnancies demonstrated better problem-solving skills than those whose mothers consumed “placebo” cereal bars.

Cons: Currently, there is no research to show that eating DHA-rich foods improves mental function in healthy adults. “It remains to be seen whether initiating DHA later in life has an important effect on the brain,” says Joseph Quinn, M.D., associate professor of neurology at Oregon Health & Science University.

Eating Well’s verdict: Eating inherently healthful foods like yogurt that have been fortified with DHA, along with foods like salmon and tuna, is a good way to increase intake of DHA, says Elizabeth Somer, R.D., author of Food & Mood (Henry Holt & Co.). And research does indicate that boosting DHA intake to about 200 mg per day–about three times what the average American gets now–may have some mental benefits. That said, don’t expect these fortified foods to help you land a spot on Jeopardy!

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