Abstract
Epidemiological 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 also reduces blood pressure in
hypertensive
rodents. The efficacy of quercetin supplementation
to lower blood pressure in hypertensive humans has never been evaluated.
We tested the hypothesis that quercetin
supplementation reduces blood pressure in hypertensive patients. We then
determined
whether the antihypertensive effect of quercetin is
associated with reductions in systemic oxidant stress. Men and women
with
prehypertension (n = 19) and stage 1 hypertension (n
= 22) were enrolled in a randomized, double-blind, placebo-controlled,
crossover study to test the efficacy of 730 mg quercetin/d
for 28 d vs. placebo. Blood pressure (mm Hg,
systolic/diastolic) 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 (P
< 0.01) systolic (−7 ± 2 mm Hg), diastolic (−5 ± 2 mm Hg), and mean
arterial pressures (−5 ± 2 mm Hg) were observed in stage
1 hypertensive patients after quercetin treatment.
However, indices of oxidant stress measured in the plasma and urine were
not affected by quercetin. These data are the first
to our knowledge to show 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.
Witma Aptriyana
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