Quercetin
Quercetin is a plant flavonoid sold as a supplement, usually at 500–1,000 mg a day, and as half of a popular "senolytic" protocol meant to clear worn-out cells. On its own it lowers systolic (top-number) blood pressure by only 2–3 mmHg in pooled trials, with weak certainty, and it can change the levels of some prescription drugs.
Quercetin has no evidence as a longevity supplement. If you take it anyway, check with a pharmacist first if you use statins, blood thinners or transplant drugs.
What it is
Quercetin is a flavonoid, one of the polyphenol compounds found in plants. As a supplement it is typically taken at 500–1,000 mg a day. It is promoted for blood pressure and, combined with the leukaemia drug dasatinib, as a senolytic: a treatment meant to clear senescent cells, worn-out cells that stop dividing and linger. The wider category of anti-aging compounds is compared on Geroprotectors.
Blood pressure: a small effect, weakly supported
A 2016 pooled analysis of randomised trials put the drop in systolic (top-number) blood pressure at about 3 mmHg.[1] But the trials disagree a lot, and the newest overview of the pooled analyses puts the drop nearer 2 mmHg and rates the certainty of the evidence very low to moderate.[2]
How much reaches the blood depends on the form. Lecithin "phytosome" forms (for example Quercefit) are absorbed far better — up to about 20 times higher blood levels in a 12-person study run by the manufacturer.[3]
The senolytic protocol: pilots, then a missed goal
The dasatinib-plus-quercetin protocol from the Mayo Clinic's Kirkland group reduced markers of senescent cells in small human pilots. The first randomised phase 2 trial, intermittent dasatinib plus quercetin in postmenopausal women, missed its primary endpoint.[4]
Dasatinib is a prescription leukaemia (chemotherapy) drug, with the bleeding, low-blood-count and fluid-around-the-lung risks that implies. This is not a home regimen, and it has no place in unsupervised use.
Drug interactions
Quercetin can change how some drugs are handled:
- Statins. In one small study in people, 500 mg a day for two weeks raised pravastatin levels by about a quarter. It did so through a liver-uptake transporter, not through CYP3A4.[5]
- CYP3A4. Its effect on CYP3A4 (cytochrome P450 3A4), the main drug-metabolising liver enzyme, is inconsistent in people and it may even speed the enzyme up.[6]
- Warfarin. There is a single case report of a stronger warfarin effect.[7]
What to do
- Don't take it for longevity. The blood-pressure effect is small and uncertain, and the senolytic use depends on a chemotherapy drug.
- Get polyphenols from food — berries, olive oil, dark chocolate and tea — rather than an isolated extract.
- On statins, blood thinners or transplant drugs? Ask a pharmacist before taking any quercetin product.
Further reading
- Serban MC et al. Effects of Quercetin on Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Am Heart Assoc 2016.[8]
- Arabi SM et al. The effects of Quercetin supplementation on cardiometabolic outcomes: An umbrella review of meta-analyses of randomized controlled trials. Phytother Res 2023.[9]
- Wu LX et al. Inhibition of the organic anion-transporting polypeptide 1B1 by quercetin: an in vitro and in vivo assessment. Br J Clin Pharmacol 2012.[10]