Reuters 10/03/00

A diet rich in fruit and vegetables may help prevent age-related mental decline, according to a US study published in the Journal of Neuroscience.

Rats fed antioxidant-rich strawberries and spinach had better memories and slower declines in nerve cell functions important in movement than rats fed standard diets, according to the report.

"Our results show that these foods, particularly spinach, may be beneficial in retarding age-related central nervous system and cognitive behavioral deficits," said lead author Dr. James Joseph of the U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts.

"Nutritional intervention with fruits and vegetables may play an important role in protecting against and possibly reversing the cognitive declines seen from aging," Joseph added in a statement released by the publisher of the journal, the Society for Neuroscience.

Fruit and vegetables are key sources of antioxidants, nutrients that disarm harmful molecules called free radicals. Free radicals — the undesirable byproducts of various metabolic functions — damage cells. Over time, this damage, called oxidative damage or oxidative stress, is believed to play a leading role in certain diseases and age-related changes. Although the body also produces antioxidants, over time, production declines.

"The brain may be particularly vulnerable to the damaging effects of free radicals because it is relatively deficient in antioxidants to begin with," Joseph said in the press statement. "Free radical destruction is thought to be a contributing factor to the decline in memory and motor performance seen in aging."

To determine whether an increase in antioxidant rich fruit and vegetable consumption might offset these age-related declines in antioxidant production, and their consequences, Joseph and colleagues fed rats four different diets. For 6 months, rats were fed either a standard diet or a standard diet supplemented with one of three factors: vitamin E, a known antioxidant; strawberry extract; or spinach. Strawberries and spinach are high in antioxidants, and also contain an array of "phytochemicals," or plant chemicals, that appear to have antioxidant properties.

Various tests designed to measure the animals' brain and mental functioning showed that the rats fed diets supplemented with spinach saw the fewest age-related declines, followed by those fed the strawberry extract. Vitamin E also helped slow mental declines over time, but not to the same extent, Joseph and colleagues report.

It may be that foods containing a variety of phytochemicals, including phytochemicals with antioxidant properties, may offer greater protection than individual nutrients, the researchers suggest.

"Thus, phytochemicals present in antioxidant rich foods, such as spinach, may be beneficial in retarding functional age-related central nervous system and cognitive behavioral deficits and, perhaps, may have some benefit in neurodegenerative disease," they conclude.

In subsequent studies, the researchers plan to test other phytochemical- and antioxidant-rich foods, such as blueberries. They also plan to investigate whether these foods can protect against or reverse mental declines associated with age-related disorders, such as Alzheimer's and Parkinson's disease. Oxidative stress may be key factor in both, recent findings suggest. Some research also suggests that supplemental doses of vitamin E, and ginkgo biloba, a source of phytochemicals, might lessen the effects of Alzheimer's.