Quercetin Supplementation Shown to Improve Hypertension.

A new study, conducted at the University of Utah and published in the Journal of Nutrition (2007, 137:2405-11), evaluated the effectiveness of quercetin supplementation in reducing hypertensive blood pressure in humans. Epidemiological studies report that quercetin, an antioxidant flavonol, is associated with reduced risk of coronary heart disease and stroke. Quercetin supplementation has been shown to reduce blood pressure in hypertensive rodents, but its efficacy in hypertensive humans was not previously evaluated.Men and women with pre-hypertension (n=19) and stage 1 hypertension (n=22) were enrolled as subjects in a randomized, double blind, placebo-controlled, crossover study to test the efficacy of a 730 mg per day quercetin supplement versus placebo for 28 days. Average blood pressure at the beginning of the study was 137/86 for pre-hypertensives subjects and 148/96 for stage 1 hypertensive subjects. Blood pressure was not altered in pre-hypertensive patients after quercetin supplementation. In contrast, reductions in systolic of 7 ± 2 mm Hg, diastolic 5 ± 2 mm Hg, and mean arterial pressures 5 ± 2 mm Hg (P < 0.01) were observed in stage 1 hypertensive patients after quercetin supplementation.Researchers also evaluated whether the antihypertensive effect of quercetin was associated with a reduction of systemic oxidant stress. However, contrary to results in animal-based studies, indicators of oxidant stress measured in subject’s plasma and urine were not affected by quercetin supplementation.Quercetin belongs to a group of plant pigments called flavonoids that are largely responsible for the colors of many fruits, flowers, and vegetables. It is found in high levels in onions, apples, tea and wine. Quercetin and related flavonoids have many health-promoting benefits: they can act as antihistamines, useful in reducing allergy symptoms, and can help reduce inflammation associated with various forms of arthritis. Quercetin also works as an antioxidant by scavenging free radicals in the body which may contribute to the aging process as well as to the development of heart disease and cancer. Antioxidants such as quercetin can neutralize free radicals and reduce or prevent the oxidative damage they cause.