Nov. 8 (HealthDay News) -- There may be truth to old adage that eating fish can make you smarter, according to three new studies.

Each suggests that fish intake, particularly the consumption of omega-3 fatty acids in fish, may improve cognitive performance.

A Norwegian study of more than 2,000 elderly people found that those who ate more than 10 grams per day of fish had markedly better test scores and a lower prevalence of poor cognitive performance than those who ate less than 10 grams of fish a day.

The more fish a person ate, the greater the effect. People who ate about 75 grams a day of fish had the best test scores.

A Dutch study of 404 people, ages 50 to 70, found that higher plasma concentrations of omega-3 fatty acid at baseline were associated with a lower decline in several cognitive measures over three years.

Finally a New Zealand study of more than 2,400 people found a strong and consistent association between circulating concentrations of the omega-3 fatty acid eicosapentaenoic acid and physical health and a less compelling link between omega-3 fatty acids and mental health.

The studies were published in the November issue of the American Journal of Clinical Nutrition.

While these are interesting observational studies, they don't establish a direct link between consumption of fish/omega-3 fatty acids and cognitive function, Dr. Irwin Rosenberg, of the Friedman School of Nutrition Science and Policy at Tufts University in Boston, wrote in an accompanying editorial. There is growing evidence of such an association, but randomized clinical trails are needed to confirm the link, he noted.

SOURCE: American Society for Nutrition, news release, Nov. 8, 2007