WASHINGTON, D.C.--Teetotalers, rejoice. Toasting with grape juice may carry brain-sparing benefits, according to research presented here 24 February at the World Parkinson's Congress. In a series of cognitive and motor tests, grape juice-drinking rats outshined their placebo-swilling counterparts, possibly due to an enhanced release of the neurotransmitter dopamine in the brain.
As many oenophiles are well aware, studies have found that drinking wine lowers the risk of heart disease, possibly by reducing blood pressure or countering the effects of "bad" (LDL) cholesterol. Similar effects have been shown for the dark purple Concord grape juice, which contains polyphenols, a class of antioxidants found in wines. But neuroscientist James Joseph of Tufts University in Boston, Massachusetts, and colleagues wanted to see if the compounds in grape juice might also serve to protect or preserve the brain--specifically, the elderly brain.
So Joseph's group focused on 19 month- old rats--pretty ancient considering most rats live less than two years. The researchers fed the rodents a diet consisting exclusively of either grape juice (10% or 50%, diluted with water) or a calorie- and flavor-matched placebo. After six weeks, the team tested the rats for motor skills such as balance, stamina, and strength. Rats on the 50% juice diet outperformed those on either the 10% juice diet or the placebo diet; they were able to hang onto a wire for an average 2 seconds longer than the others, for example.
In cognitive tests and measures of dopamine release, however, the rats on the 10% juice diet started to shine. They learned to navigate a water maze about 20 seconds faster after a trial run, compared to improvements of only 3 or 4 seconds in the other groups. They also had a 60% higher release of dopamine, compared to no change in rats on the other two diets. The release of neurotransmitters like dopamine is compromised in aging brains, says Joseph, who will also report his findings next month in Nutrition, so polyphenols and other chemicals in grape juice may help spark new communication between older brain cells. Joseph says further experiments will be needed to determine why relatively high concentrations of juice are better for some tasks than others.
The study shows "a good antioxidant might be helpful," to correct some of the damage that older neurons have sustained, says cardiologist John Folts of the University of Wisconsin, Madison. But Navindra Seeram, a nutritionist at the University of California, Los Angeles, cautions that we shouldn't start drinking grape juice like it's going out of style. A mix of antioxidants in the diet is essential, he says, so fruits and vegetables should be consumed in "the whole rainbow" of colors.
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