Does eating fish really help the brain?

A. A few years ago I’d have said that we really don’t know. Then a Chicago study claimed that if you eat two or more fish meals a week, your rate of decline in brain power with age is slower than the usual by between ten and fifteen percent. Fish-eaters’ heart rates were slower, too, than those of non-fish-eaters.

How much reliance can you put on one study? I’m not sure, but I don’t know of other studies that suggest the reverse – that eating fish harms the brain. Unless the fish are caught in places where the sea contains a lot of man-made pollution (such as mercury in the Sea of Japan).