CHICAGO — Eating two or more servings of vegetables a day may slow a person's mental decline by about 40% compared with a person who consumes few vegetables, according to a six-year study of nearly 4,000 Chicago residents age 65 or older.
Consuming lots of fruit did not appear to offer the same mental protection, although fruit has been associated with a wide variety of other health benefits, said Martha Clare Morris, chief of Rush University Medical Center's Rush Center for Healthy Aging.
The slowdown in the rate of cognitive decline experienced by people who ate 2.8 or more servings of vegetables a day is "equivalent to about five years of younger age" compared with people who ate less than one vegetable serving per day, Morris reports in today's issue of Neurology, the scientific journal of the American Academy of Neurology.
The study also suggested it may never be too late to reap the benefits of vegetable consumption. Older people who started eating more than two vegetables a day still showed a significant delay in mental decline, Morris said. One serving of a vegetable is about a cup.
The new findings come on top of two earlier Rush studies indicating that the foods people eat may significantly affect their mental agility. Morris reported four years ago that eating foods high in vitamin E appeared to reduce the risk of Alzheimer's disease, and last year she found that eating fish had a similar effect.
Vegetables, especially the green leafy type, are brimming with antioxidant compounds like vitamin E, flavonoids and carotenoids, Morris said, and vegetables contain more vitamin E than fruit does.
Eating vegetables with olive oil, vegetable oil or some other type of poly- or mono-unsaturated fats enhances the body's absorption of antioxidants, which help snuff out cell-damaging free radicals, she added.
"This study is tremendously important," said Alberto Ascherio, associate professor of nutrition and epidemiology at the Harvard School of Public Health, who found similar results over a two-year period in the Nurses Health Study of more than 120,000 nurses. "It's not easy to capture the correlation between dietary behavior and cognitive function.
"This goes in line with previous evidence supporting the potential protective effect of vegetable consumption," he said. "Each of these studies is like a small step forward. In this field we don't have the critical experiment to answer the question once and for all. We have to get to the truth by small steps. It's a long process to try to understand what we can do to reduce cognitive decline."