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Effects of the pure flavonoids epicatechin and quercetin on vascular function and cardiometabolic health: a randomized, double-blind, placebo-controlled, crossover trial.

The American journal of clinical nutrition (2015-05-03)
James I Dower, Johanna M Geleijnse, Lieke Gijsbers, Peter L Zock, Daan Kromhout, Peter C H Hollman
ABSTRACT

Prospective cohort studies showed inverse associations between the intake of flavonoid-rich foods (cocoa and tea) and cardiovascular disease (CVD). Intervention studies showed protective effects on intermediate markers of CVD. This may be due to the protective effects of the flavonoids epicatechin (in cocoa and tea) and quercetin (in tea). We investigated the effects of supplementation of pure epicatechin and quercetin on vascular function and cardiometabolic health. Thirty-seven apparently healthy men and women aged 40-80 y with a systolic blood pressure (BP) between 125 and 160 mm Hg at screening were enrolled in a randomized, double-blind, placebo-controlled, crossover trial. CVD risk factors were measured before and after 4 wk of daily flavonoid supplementation. Participants received (-)-epicatechin (100 mg/d), quercetin-3-glucoside (160 mg/d), or placebo capsules for 4 wk in random order. The primary outcome was the change in flow-mediated dilation from pre- to postintervention. Secondary outcomes included other markers of CVD risk and vascular function. Epicatechin supplementation did not change flow-mediated dilation significantly (1.1% absolute; 95% CI: -0.1%, 2.3%; P = 0.07). Epicatechin supplementation improved fasting plasma insulin (Δ insulin: -1.46 mU/L; 95% CI: -2.74, -0.18 mU/L; P = 0.03) and insulin resistance (Δ homeostasis model assessment of insulin resistance: -0.38; 95% CI: -0.74, -0.01; P = 0.04) and had no effect on fasting plasma glucose. Epicatechin did not change BP (office BP and 24-h ambulatory BP), arterial stiffness, nitric oxide, endothelin 1, or blood lipid profile. Quercetin-3-glucoside supplementation had no effect on flow-mediated dilation, insulin resistance, or other CVD risk factors. Our results suggest that epicatechin may in part contribute to the cardioprotective effects of cocoa and tea by improving insulin resistance. It is unlikely that quercetin plays an important role in the cardioprotective effects of tea. This study was registered at clinicaltrials.gov as NCT01691404.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Cholesterol, Sigma Grade, ≥99%
Sigma-Aldrich
Cholesterol, powder, BioReagent, suitable for cell culture, ≥99%
Sigma-Aldrich
SyntheChol® NS0 Supplement, 500 ×, synthetic cholesterol, animal component-free, aqueous solution, sterile-filtered, suitable for cell culture
SAFC
Cholesterol, Plant-Derived
Sigma-Aldrich
Cholesterol, from sheep wool, ≥92.5% (GC), powder
SAFC
Cholesterol, from sheep wool, Controlled origin, meets USP/NF testing specifications