Eating vegetables, not fruit, helps slow down the rate of cognitive change in older adults

Eating vegetables, not fruit, helps slow down the rate of cognitive change in older adults, according to a study published in the October 24, 2006, issue of Neurology, the scientific journal of the American Academy of Neurology.

In determining whether there was an association between vegetables, fruit and cognitive decline, researchers studied 3,718 residents in Chicago, Illinois, who were age 65 and older. Participants completed 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 percent," said study author Martha Clare Morris, ScD, with Rush University Medical Center in Chicago. "This decrease is equivalent to about five years of younger age."

Of the different types of vegetables consumed by participants, green leafy vegetables had the strongest association to slowing the rate of cognitive decline. The study also found the older the person, the greater the slowdown in the rate of cognitive decline if that person consumed more than two servings of vegetables a day.

Surprisingly, the study found fruit consumption was not associated with 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."

Morris says the study's findings can 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.