June 17, 2003
SEOUL, South Korea--A diet rich in a class of bioflavonoids, the polyphenols, may reduce the risk of chronic disease by reducing oxidative stress, according to researchers at the Sookmyung Women's University who published a study in the June issue of the Journal of the American College of Nutrition (22, 3:217-23, 2003) (www.jacn.org). Based on epidemiological evidence showing dietary polyphenols reduce the risk of chronic disease, researchers compared the effects of polyphenol-rich and -depleted diets in 19 healthy, non-smoking women.
The two dietary interventions--polyphenol-rich and -depleted--lasted six days each, separated by a three-day washout period. According to the researchers, the interventions consisted of "common foods" that were chosen based on polyphenol content. Blood and urine samples were collected at baseline, day three and day six, and researchers analyzed them for oxidative stress markers, including plasma antioxidant vitamins, erythrocyte superoxide dismutase (SOD) activity and lymphocyte DNA damage.
Plasma alpha-tocopherol and beta-carotene concentrations were slightly decreased on days three and six of the polyphenol-depleted intervention, although no change was seen during the polyphenol-rich period. Erythrocyte SOD activity was also decreased during polyphenol depletion, compared to the polyphenol-rich diet. Additionally, on day six of the polyphenol-rich intervention, SOD activity was increased by 41 percent. Researchers stated average intakes of two particular polyphenols--quercetin and kaempferol--during the polyphenol-rich diet were 21 mg/d and 9 mg/d, respectively, and average urinary excretion rates were 2.06 percent for quercetin and .46 percent for kaempferol. There were positive correlations between erythrocyte SOD activity and urinary concentration of both antioxidants, according to researchers. They concluded diets rich in polyphenols may decrease the risk of chronic disease by reducing oxidative stress.
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