March 7, 2008

Decreased Cognitive Brain Function Delayed and Reversed by Blueberries

Foods high in antioxidants reverse decreases in cognitive brain function.Studies show that blueberries contain nutrients that reverse decreases in cognitive brain function and delay cognitive brain function decline while also protecting delicate brain structures against oxidative damage.

One of the first of Agricultural Research Service neuroscientist James Joseph’s studies, published in the Journal of Neuroscience, showed a protective effect of consuming antioxidants on brain function. Study rats were fed - from adulthood to middle age - vitamin E, strawberry extracts, or spinach extracts.

Animals receiving the high-antioxidant diets did not experience the age-related cognitive performance losses seen in control rats fed their standard diet.

“Vitamins and minerals in plant foods provide protective antioxidants,” says Joseph. “But fruits, vegetables, nuts, seeds, and grains contain thousands of other types of compounds that contribute significantly to the overall dietary intake of antioxidants,” says Agricultural Research Service neuroscientist James Joseph.

A later study, also published in the Journal of Neuroscience, showed a reversal of functional loss among rats on special diets. Each of three groups of rats, equivalent in age to 63-year-old humans, was fed a different high-antioxidant extract. A control group was fed standard chow. After 8 weeks - equivalent to about 10 years in humans - the rats’ performance levels were measured.

The rats fed the spinach, strawberry, or blueberry extracts effectively reversed age-related deficits in neuronal and cognitive function. In addition, the blueberry-fed group far outperformed their peers while traversing a rotating rod to test balance and coordination.

“Despite their status as ‘senior citizens,’ those rats showed remarkable stamina on neuromotor function tests,” says psychologist and coauthor Barbara Shukitt-Hale, also with the Neuroscience Laboratory.

Examination of the brain tissue of those blueberry-fed rats showed much higher levels of dopamine than were found in the other groups. Dopamine has many functions within the brain. In particular, it can affect the way the brain controls movements.

“We suspected that the combined antioxidant potency of compounds in blueberry extract may have reduced inflammatory compounds in the brains of these older animals,” says Joseph. “Inflammation ordinarily contributes to neuronal and behavioral shortfalls during aging.”

Tests have since shown that blueberry compounds cross the blood-brain barrier and localize in rodent brain tissue.

In another study, published in the journal Neurobiology of Aging, three groups - 20 rats in each group - were studied for about three months. The control group was fed a standard diet of grain-based chow.

A second group was fed chow with blueberry extract equal to one cup daily in humans. A third group was fed chow with strawberry extract equal to one pint daily in humans.

After two months on the diets, half of the rats in each group were treated to induce the normal losses in learning and motor skills that often come with aging.

Compared to the aged control rats, the aged-but-supplemented rats were much better able to find - and in some cases remember - the location of an underwater platform.

In addition, the aged control rats had lower levels of dopamine release than the non-aged control rats. But these decreases in dopamine release were not seen in the strawberry and blueberry supplemented groups, whether aged or not.

USDA, Agricultural Research Service. Photo courtesy USDA, ARS.

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