Is fish really brain food? P.G. Wodehouse certainly thought so. In his wonderful “Jeeves” stories, Bertie Wooster encourages his brainy butler to eat more fish whenever a particularly challenging problem arises. But to what extent does fiction mirror real life? One can make a theoretical case for fish consumption based on the fact that docosahexaenoic acid, or DHA, the famous omega-3 fat in fish, is the main component of brain cell membranes, and that communication between brain cells is a function of the integrity of these membranes.
There is actually some experimental evidence to support a link between fish consumption and brain health. Infants born to mothers who consumed more fish during pregnancy have been shown to have improved verbal intelligence, better fine motor skills and pro-social behavior. A study has also correlated fish intake during pregnancy with IQ in 8-year old children. It is likely that these effects are due to increased blood levels of DHA in the offspring, but as is generally the case, the scenario is complicated. When blood is drawn from umbilical cords, it turns out that the concentration of the various fatty acids depends on the genetics both of the mother and the baby. In other words, depending on genotypes, an infant may benefit more or less from fish in the mom’s diet.
What about brain function at the other extreme of life, senior citizens? To get some insight here, researchers examined MRI brain scans of 260 individuals over the age of 65 who had normal cognitive function looking for differences associated with fish consumption as determined by dietary surveys. Subjects who ate baked or broiled but not fried fish every week had larger grey matter volumes in the areas of the brain responsible for memory and cognition. Interesting, but there was no determination as to whether these increased volumes translated to any change in brain power.
Curiously, no relationship was found with omega-3 fat intake as calculated from the diet surveys, suggesting that eating fish weekly may prevent brain ageing regardless of omega-3 content. But it may also be that eating fish is a marker for some other effect. People who ate fish were more likely to have a university education than those who didn’t. So perhaps it is mental exercise that was responsible for the changes in brain volume. There is also evidence that eating fish reduces the risk of heart disease. Maybe eating fish makes people smarter and more capable of understanding why they should be following the guidelines designed to reduce the risk of heart disease.