Was your mother right after all?
Folklore has it that “eating fish will make you smarter.” Although legends of this type are often discounted as simply old wives’ tales, some science suggests that this folkloric tale may have a degree of validity. In a series of 3 original research reports and an accompanying editorial published in the November 2007 issue of The American Journal of Clinical Nutrition, researchers provide some evidence that fish intake, in particular the intake of dietary omega-3 fatty acids (also called n–3 fatty acids) in fish, may improve cognitive performance. Crowe and colleagues assessed whether n–3 fatty acids are associated with mental and physical well-being in 2416 New Zealanders aged ≥15 years. After adjusting for a variety of factors, the investigators found a strong and consistent association between circulating concentrations of the n–3 fatty acid eicosapentaenoic acid and physical well-being although the associations between various n–3 fatty acids and mental health were less compelling. Dullemeijer and colleagues evaluated the association between plasma n–3 fatty acid concentrations and cognitive performance in 807 Dutch men and women aged 50–70 years (mean age: 60 years). A subset (n = 404) of the participants was retested 3 years later. At baseline, there was no association between plasma n–3 fatty acid concentrations and performance in any of the cognitive measures. However, higher plasma n–3 concentrations at baseline were associated with a lower decline in several of the cognitive variables over the 3-year follow-up period. Nurk and colleagues examined the relation between consumption of seafood products and cognitive performance in 2031 elderly Norwegians. The subjects underwent a series of cognitive tests, and dietary intake was carefully evaluated for fish and fish product consumption. The subjects whose mean daily intake of fish was ≥10 g had markedly better mean test scores and a lower prevalence of poor cognitive performance than did those whose intake was <10 g. This effect was dose dependent, with the best test scores occurring in individuals consuming approximately 75 g/day. Interestingly, consumption of lean fish appeared to be as effective as fattier fish, which suggests that the effects were due to something other than n–3 fatty acids. In an editorial published along with these reports, Rosenberg from the Friedman School of Nutrition Science and Policy at Tufts University in Boston, MA, commends these research groups for addressing the association of fish and n–3 fatty acid intake with cognitive function in individuals not yet showing signs of impaired cognitive function. He also points out, however, that these observational studies fall short of proving a causal effect. Nonetheless, although randomized controlled trials are still needed in this area, the long-standing wives’ tale that “eating fish will make you smarter” is gaining substantial evidence.
Source: The American Journal of Clinical Nutrition, November 2007
