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Quercetin, an antioxidant found many foods including onions, berries and apples, is associated with a reduced risk of heart disease and stroke. Supplementation with quercetin has been shown to reduce hypertension in animal models, but until now has never been tested in hypertensive humans.

Researchers at the University of Utah, in collaboration with USANA Health Sciences, conducted a randomized, double-blind, placebo-controlled, crossover study to test the effectiveness of quercetin supplementation in lowering unhealthy blood pressure levels. The subjects were divided into two groups: prehypertensives (120-139 mm Hg systolic/80-89 mm Hg diastolic) or stage 1 hypertensives (140-159 mm Hg systolic/90-99 mm Hg diastolic). The participants were given either 730 mg quercetin/day or placebo for 28 days.

Blood pressure remained unchanged in prehypertensives after supplementation with quercetin. In contrast, stage 1 hypertensive subjects showed significant reductions in both systolic (-7 mm Hg) and diastolic (-2 mm Hg) blood pressure after quercetin supplementation. This is the first published study to show that quercetin supplementation can reduce blood pressure in hypertensive adult humans. Additionally, it is important to note that quercetin supplementation did not influence the blood pressure of non-hypertensive individuals.

J. Nutr. 137:2405-2411, November 2007