Quercetin reduces blood pressure

Original Internist, March, 2008 by Donald Brown

Reference: Edwards RL, Lyon T, Litwin SE, et al. Quercetin reduces blood pressure in hypertensive subjects. J Nutr 2007;137:2405-11.

Design: Randomized, double-blind, placebo-controlled, crossover trial

Participants: Males and females with either prehypertension (120-139 mm Hg systolic/80-89 mm Hg diastolic; n = 19; mean age 47.8 [+ or -] 3.5 years old) or stage 1 hypertension (140-159 mm Hg systolic/90-99 mm Hg diastolic; n = 22; mean age 49.2 [+ or -] 2.9 years old) were enrolled in the study. Subjects taking antihypertensive medications were not allowed in the study.

Study Medication and Dosage: 365 mg of quercetin aglycone b.i.d. (USANA Health Sciences, Salt Lake City, Utah) or placebo.

Duration: Four weeks of treatment with either quercetin or placebo followed by a 14-day washout phase. This was followed by cross-over and another 14-day treatment period on either quercetin or placebo. Patients were randomized after an initial 14-day run-in period.

Outcome Measures: The change in blood pressure (BP) compared to baseline measurement was the primary outcome measure. Secondary outcomes included the effect of quercetin on measures of oxidant stress measured in the plasma and urine. Additionally, blood samples were used to measure plasma quercetin concentrations as well as blood lipid concentrations (triglycerides, LDL-C, HDL-C, VLDL-C, and total lipoprotein concentrations).

Key Findings: BP was not changed in prehypertensive patients following supplementation with quercetin nor did it change during the placebo phase of the study. In stage 1 hypertensive patients, quercetin supplementation significantly reduced systolic BP (-7 [+ or -] 2 mm Hg; p < 0.01), diastolic BP (-5 [+ or -] 2 mm Hg; p < 0.01), and mean arterial pressures (-5 [+ or -] 2 mm Hg; p < 0.01). The antihypertensive effect of quercetin was independent of gender, age, and BMI in stage 1 hypertensive patients. Indices of oxidative stress in the plasma and urine were unaffected by quercetin in both groups. Also, there was no effect on blood lipid concentrations during quercetin supplementation.

Practice Implications: Based on the results of animal studies demonstrating the effect of quercetin on vasorelaxation and blood pressure, researchers from the University of Utah decided to see if quercetin was able to reduce BP in prehypertensive and stage 1 hypertensive human subjects. The crossover design of the study suggests that a daily dose of 730 mg of quercetin (in an aglycone form) is capable of reducing both systolic BP and diastolic BP in stage 1 hypertensive patients but not prehypertensive patients. Hopefully this study will set the stage for future dose-response studies as well as a larger placebo-controlled trial with stage 1 hypertensive patients.

Submitted by Emerson Ecologics

Author: Donald Brown, ND