Eating three portions of green leafy, yellow and cruciferous vegetables every day probably won't make you more brilliant, but it may significantly slow down the decline in cognitive function that starts around age 40.

A recent six-year study of the eating habits of some 3,700 elderly Chicago residents concluded that consumption of an average of 2.8 vegetable servings daily was associated with a 40 percent decrease in cognitive decline compared to those who ate an average of about one vegetable serving a day. That is equivalent to being about five years younger.

Researchers linked the results to vitamin E in the vegetables. Fruits in the diet showed no effect on cognitive aging.