A nutritious diet rich in fruits, vegetables, and whole grains and that is low in fat and added sugar can reduce the risks of many chronic conditions, including heart disease, diabetes, obesity, and some forms of cancer. In recent years, investigators have used epidemiologic, animal, and test tube studies and clinical trials to explore whether diet can play a role in preserving cognitive function or even reducing risk of AD.

A long-held theory about aging suggests that, over time, damage from free radicals (molecules that chemically react easily with other molecules) can build up in neurons, causing loss of function. This damage is called oxidative damage. The brain’s unique characteristics, including its high rate of metabolism and its long-lived neurons, may make it particularly vulnerable to oxidative damage. Previous epidemiologic and laboratory studies have suggested that fruits and vegetables that are high in antioxidants might protect the brain against this kind of damage. A group of Harvard Medical School researchers explored this possibility by examining data from more than 13,000 Nurses’ Health Study participants aged 70 and older (Kang et al., 2005). They found that the women who ate the most vegetables—especially green leafy vegetables (like spinach and romaine lettuce) and cruciferous vegetables (like broccoli and cauliflower)—experienced a slower rate of cognitive decline than did women who ate the least vegetables. The scientists were careful to account for other factors that might influence the results, such as use of vitamin supplements, physical activity, smoking and alcohol use, and educational attainment. Interestingly, fruit consumption did not appear to be associated with any change in cognitive ability. The scientists speculate that the abundant antioxidant and folate (a nutrient that appears to be important for proper neural activity and