Researchers study fruit consumption and antioxidants
June 12, 2007
by Jeff Gelski
LITTLE ROCK, ARK. — Researchers have taken an initial step in establishing dietary recommendations for antioxidants by measuring the plasma (blood) antioxidant capacity (AOC) of volunteers who had ingested blueberries, cherries, dried plums dried plum juice, grapes, kiwifruit or strawberries. Ronald Prior, a chemist who works at the Arkansas Children’s Nutrition Center in Little Rock, led the U.S. Department of Agriculture’s Agricultural Research Service study.
Eating grapes and kiwifruit both led to noticeable spikes in plasma AOC, but researchers said it was not clear which compounds were responsible for the increased levels. For wild blueberries, a half-cup serving was needed to boost AOC levels.
Although plums have a high antioxidant content, consuming them did not raise plasma AOC levels in volunteers. Chlorogenic acid, one of the major phytochemicals in plums, is not readily absorbed by humans, Mr. Prior said. Researchers also found that when volunteers consumed a shake containing protein, carbohydrates and fat and no antioxidants, their antioxidant levels dropped.
In conclusion, the researchers said, "Without further long-term clinical studies, one cannot necessarily translate increased plasma AOC into a potential decreased risk of chronic degenerative disease.
"Preliminary estimates of antioxidant needs based upon energy intake were developed. Consumption of high antioxidant foods with each meal is recommended in order to prevent periods of postprandial oxidative stress."
The study involved five clinical trials with 6 to 10 subjects per experiment. Findings appeared in the April issue of the Journal of the American College of Nutrition.