Effects of a quercetin-rich onion skin extract on 24 h ambulatory blood pressure and endothelial function in overweight-to-obese patients with (pre-)hypertension: a randomised double-blinded placebo-controlled cross-over trial

Study answer

What this study found

Quercetin did not significantly improve 24 h ambulatory blood pressure, office blood pressure, endothelial function, or inflammatory and oxidative markers in the total study population. In the hypertensive subgroup, quercetin lowered mean 24 h systolic BP by -3.6 (SD 8.2) mmHg from baseline (P = 0.022) and the treatment difference versus placebo was -3.9 (SD 11.1) mmHg (P = 0.049). Day-time systolic BP decreased by -4.6 (SD 9.0) mmHg (P = 0.014) and night-time systolic BP decreased by -6.6 (SD 9.9) mmHg (P = 0.007). No adverse events were reported during either treatment.

Study & population

Randomised, double-blinded, placebo-controlled crossover trial in overweight-to-obese adults with pre-hypertension or stage I hypertension recruited from the community in Bonn, Germany.

Intervention

Participants received a quercetin-rich onion skin extract orally at 162 mg quercetin per day, given as three capsules daily with the principal meals for 6 weeks.

Key limitation

The overall sample was small, and the main blood pressure benefit appeared only in an exploratory hypertensive subgroup analysis.

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Original abstract