Outcome
    Moderate Evidence

    Quercetin for Heart Health Support

    Quercetin produces small reductions in blood pressure in meta-analysis, most evident at doses above 500mg daily and in people with hypertension. Effects on lipids and clinical events are unproven.

    Overview

    Quercetin produces small reductions in blood pressure in meta-analysis, most evident at doses above 500mg daily and in people with hypertension. Effects on lipids and clinical events are unproven.

    Verdict

    Mixed evidence

    How It Works

    Quercetin improves endothelial function by increasing nitric oxide bioavailability, both by upregulating endothelial nitric oxide synthase and by reducing superoxide-mediated nitric oxide breakdown. Improved endothelium-dependent vasodilation is the most consistently reported vascular effect. It also inhibits ACE activity in vitro and reduces NF-kB-driven vascular inflammation and adhesion molecule expression, processes involved in early atherosclerosis. As elsewhere with quercetin, the gap between in-vitro potency and achievable plasma concentrations tempers expectations for the clinical effect.

    Dosing & Protocol

    Typical dose

    Recommended dose
    500-1,000 mg/day quercetin in divided doses with food; blood pressure effects are modest and lipid effects inconsistent
    Expected timeframe
    8-12 weeks

    Protocol

    form
    Bioavailability-enhanced quercetin - phytosome or enzymatically modified isoquercitrin - given poor absorption of the plain aglycone
    duration
    8-12 weeks
    co factor
    Take with food containing fat; monitor blood pressure at home. Evidence is mixed. Meta-analyses of randomised trials show quercetin reduces systolic blood pressure by roughly 3-5 mmHg and diastolic by 2-3 mmHg, with effects concentrated at doses of 500 mg/day or more and in trials lasting 8 weeks or longer, and larger effects in people with hypertension or metabolic syndrome. Effects on LDL, HDL and triglycerides are inconsistent across trials. Mechanisms include improved endothelial nitric oxide availability, reduced oxidative stress and possible ACE inhibition. No trial has examined cardiovascular events.
    titration
    Increase to 500 mg twice daily; meta-analyses found blood pressure effects mainly at doses of 500 mg/day and above
    starting dose
    500 mg once daily with a fat-containing meal

    Evidence

    What the studies say

    Meta-analyses of randomised trials report modest reductions in systolic and diastolic blood pressure with quercetin supplementation, with subgroup analyses suggesting effects concentrated at doses of 500mg daily or more, durations beyond eight weeks, and in hypertensive participants. Some trials also report improved flow-mediated dilation. Effects on LDL cholesterol, HDL and triglycerides have been inconsistent across trials, and no study has assessed cardiovascular events. Trials are small and use widely differing formulations. Quercetin inhibits CYP3A4 and P-glycoprotein, which is a practical concern for anyone on statins, calcium channel blockers, anticoagulants or immunosuppressants.

    Effects of Quercetin on Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

    Score: 9/10
    2016
    meta_analysis
    n=587

    Serban MC, Sahebkar A, Zanchetti A +2 more

    significant reductions both in systolic BP (WMD: -3.04 mm Hg) and diastolic BP (WMD: -2.63 mm Hg) following supplementation with quercetin

    View source

    Safety

    Caveats

    A 3-5 mmHg reduction is real but small - roughly what you get from reducing salt intake or losing a few kilograms, and far less than antihypertensive medication. Do not stop or reduce prescribed blood pressure or lipid medication. Weight loss, reduced sodium, the DASH dietary pattern, physical activity, limiting alcohol and stopping smoking all produce larger effects, and statins have outcome evidence that no supplement matches. Safety of quercetin: up to 1,000 mg/day for up to 12 weeks is the well-studied ceiling; longer durations and higher doses are not well characterised, and renal toxicity has been reported with high intravenous doses. The interaction profile matters here specifically - quercetin inhibits CYP3A4 and P-glycoprotein, which can raise levels of statins, calcium channel blockers such as amlodipine and felodipine, ciclosporin and digoxin, and it may interact with warfarin. Combined with antihypertensives it may cause additive lowering, so monitor for dizziness. It can also reduce the efficacy of quinolone antibiotics. Use caution in kidney disease. Avoid in pregnancy and breastfeeding - hypertension in pregnancy needs specialist management. Chest pain or exertional breathlessness needs medical assessment.

    Less likely to help if

    People with normal blood pressure, and anyone needing substantial reductions.

    Medical Disclaimer

    The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.

    Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.