Experts believe a decline in memory and cognitive function is a normal consequence of aging. However, eating vegetables, but not fruit, might slow down the rate of this cognitive change in older adults, according to a study, "Associations Of Vegetable And Fruit Consumption With Age-Related Cognitive Change," published in the October 24, 2006, issue of Neurology, the scientific journal of the American Academy of Neurology. The study was supported by grants from the National Institute on Aging.
Researchers studied 3,718 Chicago residents, age 65 and older, to determine whether vegetable and fruit consumption were associated with cognitive decline. Study participants filled out a food-frequency questionnaire and received at least two cognitive tests over a six-year period.
"Compared to people who consumed less than one serving of vegetables a day, people who ate at least 2.8 servings of vegetables a day saw their rate of cognitive change slow by roughly 40%," said study author Martha Clare Morris, ScD, Rush University Medical Center, Chicago. "This decrease is equivalent to about five years of younger age."
Green leafy vegetables showed the strongest association to decreased rate of cognitive decline. The study also found the older the person was, the more the rate of their cognitive decline slowed if they consumed more than two servings of vegetables a day. However, the study found no association between fruit consumption and cognitive change.
"This was unanticipated and raises several questions," said Morris. "It may be due to vegetables containing high amounts of vitamin E, which helps lower the risk of cognitive decline. Vegetables, but not fruits, are also typically consumed with added fats such as salad dressings, and fats increase the absorption of vitamin E. Still, further study is required to understand why fruit is not associated with cognitive change."
An earlier study by the author (Morris, MC, et al. "Vitamin E and Cognitive Decline in Older Persons," Archives of Neurology, Jul 2002;59:1125-1132) showed that people who had a slower mental decline also had the largest intake of vitamin E when compared to those who had smaller amounts of vitamin E in their diet.
Morris points out that the study's findings should be used to simplify public-health messages by saying people should eat more or less of foods in a specific food group, not necessarily more or less of individual foods.
