Effects of the pure flavonoids epicatechin and quercetin on vascular function and cardiometabolic health: a randomized, double-blind, placebo-controlled, crossover trial.
What this study found
Overall, epicatechin did not significantly improve the primary vascular endpoint, and quercetin-3-glucoside did not improve vascular function or most cardiometabolic markers. For epicatechin, chronic flow-mediated dilation was not significant (1.08, 95% CI -0.09 to 2.26; P=0.07), but fasting insulin and insulin resistance improved (insulin -1.46, 95% CI -2.74 to -0.18; P=0.03; HOMA-IR -0.38, 95% CI -0.74 to -0.01; P=0.04). Most other outcomes, including blood pressure, pulse wave velocity, lipids, glucose, and body weight, were unchanged. These findings suggest a possible insulin-sensitivity…
- Study & population
- Randomized, double-blind, placebo-controlled crossover trial conducted in apparently healthy older adults in the Netherlands.
- Intervention
- In the active treatment periods, participants received oral (2)-epicatechin 100 mg/day or quercetin-3-glucoside 160 mg/day, each provided as 2 capsules per day, one with breakfast and one with dinner, for 4 weeks.
- Key limitation
- The active arms were small and the intervention periods were short at 4 weeks, limiting power to detect modest effects and long-term clinical relevance.
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Open PDFOriginal abstract
BACKGROUND 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). OBJECTIVE We investigated the effects of supplementation of pure epicatechin and quercetin on vascular function and cardiometabolic health. DESIGN 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. RESULTS 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. CONCLUSIONS 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.