Quercetin
Also known as: quercetin glycoside, quercetin dihydrate, 3,3',4',5,7-pentahydroxyflavone, bioflavonoid
Effective Dosage
500 mg daily based on available study data (limited human trials)
What the Science Says
Quercetin is a naturally occurring plant pigment (flavonoid) found in foods like onions, apples, and berries. In human studies, it has been tested primarily as part of multi-ingredient blends, where combinations including quercetin reduced markers of oxidative stress (like malondialdehyde) in older adults and people with Alzheimer's disease. One small trial found a single 500 mg dose of quercetin glycoside affected motor unit recruitment in older adults during resistance exercise, though the practical significance is unclear. Most promising findings — including effects on liver fibrosis, muscle health, and cancer — come from animal or lab studies, not human clinical trials.
What It Doesn't Do
Not proven to boost immunity on its own in humans — the immune studies used multi-ingredient formulas. No human evidence it treats or prevents cancer. Not shown to build muscle or improve athletic performance in humans. The anti-aging and 'senolytic' claims circulating online have no support from the studies provided here. Don't expect it to lower cholesterol based on current human data — that evidence is theoretical.
Evidence-Based Benefits
Quercetin has shown symptomatic improvement in an open-label trial for interstitial cystitis, with significant reductions in pain and symptom indices after 4 weeks at 500 mg twice daily, though this lacked a placebo control (PMID: 11272677). It has demonstrated anti-inflammatory effects via NLRP3 inflammasome inhibition in animal models of pre-eclampsia when combined with aspirin (PMID: 36136273). In vitro, quercetin protected endothelial progenitor cells from high-glucose-induced damage through Sirt1-dependent eNOS upregulation, suggesting potential vascular benefits in diabetic contexts (PMID: 25197782).
Weak EvidenceEffective at: 500-1000 mg/day based on clinical study doses (No established optimal dose from provided studies)
Source: auto-research
Absorption & Bioavailability
Poor to Moderate — quercetin has well-known absorption challenges; glycoside forms (like quercetin glycoside) are generally better absorbed than aglycone forms, but no pharmacokinetic data was provided in the studies reviewed.
Red Flags to Watch For
- Most human studies use quercetin in multi-ingredient blends, making it impossible to isolate quercetin's specific contribution
- Animal and lab findings (liver fibrosis, cancer, muscle) are frequently overstated in marketing — human evidence is very limited
- No established safe upper dose from the provided studies; one animal study used very high doses (1.25 g/kg body weight in rats) not applicable to humans
- Widely available in supplements with 1,000+ registered products, but commercial doses are rarely validated by clinical trials
- Potential interactions with medications (not addressed in provided studies) are a known concern with flavonoids at high doses
Products Containing Quercetin
See how Quercetin is used in these analyzed products:
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-04-06