November 7, 2007
SALT LAKE CITYEpidemiological studies report that quercetin, an antioxidant flavonol found in apples, berries, and onions, is associated with reduced risk of coronary heart disease and stroke. Quercetin supplementation reduces blood pressure in hypertensive rodents, however, the efficacy of quercetin supplementation to lower blood pressure in hypertensive humans has never been evaluated until researchers at the University of Utah tested the hypothesis (American Society for Nutrition J. Nutr . 2007; 137:2405-11). They then determined whether the antihypertensive effect of quercetin is associated with reductions in systemic oxidant stress. Men and women with prehypertension and stage 1 hypertension were enrolled in a randomized, double blind, placebo-controlled, crossover study to test the efficacy of 730 mg quercetin/d for 28 days versus placebo. Blood pressure at enrollment was 137 ± 2/86 ± 1 in prehypertensives and 148 ± 2/96 ± 1 in stage 1 hypertensive subjects. Blood pressure was not altered in prehypertensive patients after quercetin supplementation. In contrast, reductions in systolic, diastolic, and mean arterial pressures were observed in stage 1 hypertensive patients after quercetin treatment. Indices of oxidant stress measured in the plasma and urine were not affected by quercetin. This results shows that quercetin supplementation reduces blood pressure in hypertensive subjects. Contrary to animal-based studies, there was no quercetin-evoked reduction in systemic markers of oxidative stress.
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