TUESDAY, July 16, 2002 (HealthDayNews) -- Eating more fruits and vegetables has always been smart, but new research shows just how smart it is.

Two new animal studies have found that antioxidants in fruits and vegetables can improve learning and memory, and they minimize the effect of aging on the brain. Certain foods do a better job of this, the studies show, because they have higher levels of antioxidant activity.

Antioxidants can undo cell damage caused by renegade "free radical" molecules, and previous studies have shown they can prevent disease and improve mental functioning, among other things.

"What we have done is focus on the fruits and vegetables high on the U.S. Department of Agriculture (USDA) list of antioxidants," says Paula Bickford, a senior career scientist at the James A. Haley Veterans Hospital in Tampa and lead author of both studies, just published in the Journal of Neuroscience.

The USDA ranks foods by their antioxidant content. Spinach, spirulina (an algae often sold in capsule form in health food stores) and apples were particularly beneficial for learning and memory, Bickford says.

In the first study, the researchers fed a group of rats a diet rich in spinach, while another group got regular rat chow, all for six weeks. The rats were then measured for their performance on a traditional learning test: They were exposed to a tone, then exposed to a puff of air to the eye. The researchers studied how long it took rats in each group to learn to blink to avoid the air puff.

"The ones on spinach learned to make the association with fewer trials," Bickford says. "By the third day, they were at their learning maximum. It took the [other] rats five or six days to learn.

"We think that what we are experiencing [in the rats] is an improvement in neuron functioning. Because we improve the ability of the neurons to communicate, it is easier for the animals [on the spinach-enriched diets] to learn," she adds.

In the second study, the researchers compared three types of diets, again fed to rats: one group got a diet enriched with spirulina (high in antioxidants), another group got apples (moderate in antioxidant activity), and a third got cucumber, which is low in antioxidants.

"Initially, I was amazed," Bickford says. "We were seeing effects within two weeks with the apple and spirulina diets."

When the rats' brain functioning was evaluated, the researchers found the accumulation of inflammatory substances in the brain that typically occurs with age had been reversed in those on the apple and spirulina diets, and that they had better neuron functioning.

The amount of apple in the apple-enriched diet, for instance, was about 1 percent of the diet, Bickford says, which translates to about an apple a day.

Bickford can't say the study applies to humans, but she thinks it might.

"I've always eaten a lot of fruits and vegetables," she says. Since the study results, she's boosted her intake even more, she adds.

Another antioxidant researcher says the study is interesting, but not yet reason enough to change your diet.

"We have done similar studies," says Raj Sohal, a professor of molecular pharmacology and toxicology at the University of Southern California School of Pharmacy in Los Angeles.

In one instance, Sohal and his team gave animals supplements of the antioxidant vitamin E and found it improved memory in up to 15 percent of the animals.

The unanswered question, he says, is, "to what extent are we correcting a deficiency?" When and if that is the case, he adds, someone who already gets the recommended amounts of antioxidants may not benefit by taking even higher amounts.

"These are just preliminary," he says of the Florida studies. "They have to be replicated. The study is interesting in the sense that these kinds of studies are needed."

However, it shouldn't, for instance, cause a cucumber lover to give up the vegetable, he adds.

What To Do

For information on antioxidant levels in fruits and vegetables, see the U.S. Department of Agriculture.

For information on forgetfulness, see National Institutes on Aging.

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