In recent years, biochemists have been touting the virtues of resveratrol. This constituent of grapes not only functions as a potent antioxidant but also possesses the ability to fight inflammation. Indeed, a grapes resveratrol has been tendered as at least a partial explanation for why moderate consumption of grape juice or wine cuts an individuals risk of heart disease. Now scientists with the U.S. Department of Agriculture find that peanuts offer another rich dietary source of this chemical.
Though several studies had previously turned up resveratrol in peanuts, invariably those legumes had been sick -- deliberately inoculated with a fungal infection and left to incubate the blight, observes Timothy H. Sanders, a plant physiologist with USDAs Market Quality and Handling Research Laboratory in Raleigh, N.C. Since resveratrol belongs to a class of compounds (phytoalexins) that help plants cope with disease and other forms of stress, this finding wasnt surprising, he says. But the question lingered about whether the healthy peanuts marketed for human consumption would also contain this compound.
Sanders and his colleague Robert W. McMichael chemically analyzed healthy samples of the four different types of peanuts grown in the United States: Virginias, runners, Spanish, and a new cultivar bred to produce a high proportion of its fat in the form of relatively healthy monounsaturates. All four types produce resveratrol in amounts ranging from 1.7 to 3.7 micrograms per gram of peanut. Sanders team plans to report these results at the American Chemical Society meeting in Las Vegas next month.
In general, Sanders data suggest that a 1-ounce serving of goobers -- a small handful -- contains about 70 micrograms of resveratrol. Though thats less than one-tenth the amount in a serving -- 5 (fluid) ounces -- of wine, its still substantial, Sanders says.
Moreover, he points out, its far from the only beneficial ingredient in peanuts. These popular legumes also offer a healthy dose of folic acid, vitamin E, fiber, and zinc.
The latter, by the way, is a nutrient that plays an important role in cognition and memory. Indeed, a new study by James A. Penland, Sanders colleague at USDAs Grand Forks (N.D.) Human Nutrition Research Center, shows that Chinese grade-school children whose zinc-deficient diets were supplemented with the mineral outperformed unsupplemented peers on tests of perception, memory, and reasoning.
Currently, Penland observes, some 6 percent of grade-school boys and 10 percent of girls in the United States also fail to consume the recommended daily allowance (RDA) of zinc. Those children could pick up much of that RDA without the need for supplements by merely eating a peanut-butter sandwich made with whole-wheat bread.
If peanut butter also contains the resveratrol seen in fresh peanuts -- and Sanders says theres no reason to think it wouldnt -- then adults might also gain some health benefits from such a sandwich. In fact, they might derive a double-whammy, since the latest resveratrol studies suggest that this compound not only fights heart disease but also cancer (see Versatile cancer weapon in grapes).
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James A. Penland
Grand Forks Human Nutrition Research Center
Grand Forks, ND 58201
Timothy H. Sanders
Market Quality and Handling Research
North Carolina State University
Raleigh, NC 27695
This week's Food for Thought is prepared by Janet Raloff, senior editor of Science News.