Supplements
quercetin decreases cancer risk
In plain terms: Does quercetin prevent cancer?
Leans support Supplements 🔬 Includes disconfirming
Part of: 🧪 quercetin
RefutedContestedStrong support
consensus score 0.27
The evidence is scattered and site-by-site: a repeated hint for lung cancer, a clean null for ovarian, and for prostate the biggest analysis found MORE cancer, not less. None of it can separate quercetin from the fruit and vegetables that contain it.
📅 Last reviewed: 2026-07-26 ⓘ
Evidence ladder
How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."
Top evidence so far: All trials, pooled (Meta-analysis)
MechanismIn-vitroAnimalObservationalRCTMeta-analysis
How the studies fall
6 support 4 contradict 0 tested null 11 mixed · 21 sources, 9 independent groups
What the evidence shows
Loud evidence and relevant evidence are two different literatures here. The overwhelming majority of "quercetin anticancer" work is cell-line and rodent research that carries no implication for human risk. The human evidence is dietary-flavonol epidemiology, and it is scattered and site-inconsistent: the most repeated inverse association is lung cancer (OR ~0.66-0.
The evidence (21)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| Xie Y et al 2016 · study_type: meta-analysis | meta-analysis | mixed | moderate | Meta-analysis of 12 human population studies (4,593 cases, 519,378 controls) found dietary flavonol intake associated with reduced gastric cancer risk (OR 0.80, 95% CI 0.70-0.91) but no significant association with esophageal cancer (OR 0.8 |
| Amjadi A et al 2026 · study_type: meta-analysis | meta-analysis | supports | moderate | Umbrella review of 6 meta-analyses (27 effect sizes) of human observational studies found dietary polyphenol intake associated with an 11% lower risk of digestive-system cancers overall (RR 0.89, 95% CI 0.85-0.93), with a flavonol/quercetin |
| Zamora-Ros R et al 2014 · study_type: observational | observational | supports | moderate | EPIC cohort (477,312 participants across 10 European countries, 1,575 incident bladder cancer cases, ~11y follow-up) found dietary flavonol intake inversely associated with bladder cancer risk (HR 0.74, 95% CI 0.61-0.91, top vs. bottom quin |
| Zhou Y et al 2023 · study_type: observational | observational | supports | low | NHANES population-based cohort (14,029 participants, 405 cancer deaths over ~117 months) found dietary flavonol intake inversely associated with all-cause cancer mortality across quartiles vs. lowest (HR ~0.54-0.58, p=0.02-0.05), with effec |
| Duan X et al 2025 · study_type: animal | animal | mixed | low | Meta-analysis of preclinical animal studies found quercetin treatment reduced tumor/precancerous lesion markers and cell proliferation (PCNA SMD -8.22) in rodent colorectal-cancer models. The authors themselves note human clinical research TEMPERED: preclinical (cell-line/animal) work — carries no implication for human cancer RISK, which is what this claim asserts. |
| Kubina R et al 2021 · Nutrients | in-vitro | mixed | low | Systematic review of PRECLINICAL (in-vitro/animal) studies only, on quercetin/fisetin/kaempferol's antiproliferative and proapoptotic activity in head & neck cancer cell lines and signaling pathways. No human dietary-intake or risk data pre TEMPERED: preclinical (cell-line/animal) work — carries no implication for human cancer RISK, which is what this claim asserts. |
| Chang H et al 2018 · Nutrients | meta-analysis | supports | moderate | Meta-analysis of 12 studies (5 cohort, 7 case-control; 17,481 cases/740,859 controls): highest vs lowest flavonol intake (class including quercetin) OR=0.70 (0.54-0.90) for colon cancer, but no significant effect on rectal cancer (OR=0.93, |
| Yi G et al 2026 · study_type: in-vitro | in-vitro | mixed | low | Narrative/mechanistic review synthesizing preclinical findings on quercetin's anti-cancer activity and its bidirectional interplay with gut microbiota (microbial biotransformation yielding tumor-suppressive metabolites). Entirely a synthesi TEMPERED: preclinical (cell-line/animal) work — carries no implication for human cancer RISK, which is what this claim asserts. |
| Rostampour K et al 2025 · Nutrition and cancer | meta-analysis | supports | moderate | GRADE-assessed meta-analysis of 20 observational studies: quercetin intake OR=0.66 (95% CI 0.48-0.91, p=0.01) for lung cancer, alongside similar inverse signals for other flavonoid subclasses. Dietary-intake design cannot isolate quercetin |
| Huang Y et al 2024 · study_type: meta-analysis | meta-analysis | contradicts | moderate | Meta-analysis of 38 human observational studies (11 cohort, 27 case-control; n=824,933) found dietary flavonol intake associated with a small but statistically significant INCREASE in prostate cancer risk (OR 1.05, p=0.042), opposite to the |
| El-Mansy MN et al 2026 · study_type: animal | animal | mixed | low | Hamster DMBA-induced oral carcinogenesis model: oral quercetin (25 mg/kg, 3x/week) reduced Ki-67/Bcl-2 expression and carcinoma severity versus DMBA-only controls. Animal chemoprevention model at pharmacologic dose, not a human dietary-inta TEMPERED: preclinical (cell-line/animal) work — carries no implication for human cancer RISK, which is what this claim asserts. |
| Wang K et al 2024 · study_type: observational | observational | supports | low | NHANES cohort of 6,110 hypertensive US adults (43,977 person-years, 265 cancer deaths) found higher flavonol intake associated with lower cancer-related mortality (HR 0.52, 95% CI 0.28-0.96), while total-flavonoid intake alone showed no sig |
| Bandera EV et al 2009 · Cancer causes & control : CCC | observational | mixed | low | Case-control study (424 endometrial cancer cases, 398 controls): quercetin intake showed a borderline inverse association (OR=0.65, 95% CI 0.41-1.01, highest vs lowest quartile, p-trend=0.02). Confidence interval crosses the null; small cas |
| Gates MA et al 2009 · International journal of cancer | observational | contradicts | moderate | Large case-control study (1,141 ovarian cancer cases, 1,183 controls) testing 5 individual flavonoids: quercetin intake showed no significant association with ovarian cancer risk; only apigenin showed a borderline inverse association (RR=0. |
| Li H et al 2024 · study_type: meta-analysis | meta-analysis | mixed | low | Umbrella review of 32 meta-analyses/systematic reviews found dietary flavonoid intake (mostly total flavonoids, not flavonol-isolated) inversely associated with breast, colorectal, and lung cancer but positively associated with prostate can |
| Simons CC et al 2009 · study_type: observational | observational | contradicts | moderate | Netherlands Cohort Study (120,852 participants, ~2,485 colorectal cancer cases, 13.3y follow-up) found NO overall association between dietary flavonol, flavone, or catechin intake and colorectal cancer endpoints. A protective catechin (not |
| Shahid B et al 2026 · study_type: in-vitro | in-vitro | mixed | low | Systematic review of 24 preclinical studies (16 in vitro cell-line, 8 in vivo animal) found quercetin/kaempferol reduced cancer cell viability and induced apoptosis in lung, breast, and colorectal models via PI3K/Akt, MAPK, NF-kB, and p53 p TEMPERED: preclinical (cell-line/animal) work — carries no implication for human cancer RISK, which is what this claim asserts. |
| Wang Z et al 2026 · study_type: animal | animal | mixed | low | In vitro HCC cell lines plus mouse xenograft model: quercetin dose-dependently suppressed EGFR/PI3K/AKT/GSK3β signaling and reduced HBV-associated hepatocellular carcinoma tumor growth. Preclinical mechanism/xenograft study at experimental TEMPERED: preclinical (cell-line/animal) work — carries no implication for human cancer RISK, which is what this claim asserts. |
| Woo HD et al 2013 · PloS one | meta-analysis | mixed | moderate | Meta-analysis of 35 studies (19 case-control, 15 cohort; ~1M subjects total) found dietary quercetin (and kaempferol) intake significantly associated with decreased smoking-related cancer risk (aerodigestive tract/lung) only in smokers, wit |
| Parvaresh A et al 2016 · Journal of research in medical sciences : the official journal of Isfahan University of Medical Sciences | observational | contradicts | low | Narrative systematic review (13 total studies: only 1 prospective + 2 case-control in humans, rest animal/in-vitro) concluded epidemiological data did NOT show quercetin significantly decreases ovarian cancer risk at typical dietary intake |
| Reale G et al 2018 · study_type: observational | observational | mixed | low | Case-control study (118 prostate cancer cases, 222 controls, Sicily): high flavonol intake OR=0.19 (0.06-0.56) and catechin intake OR=0.12 (0.04-0.36) associated with reduced prostate cancer risk; flavanones were positively associated with TEMPERED: small (118-case) recall-bias-prone case-control whose protective prostate finding directly contradicts the far larger prostate meta-analysis; a genuine disagreement, not support. |
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Educational only, not medical advice. Grades and scores reflect published evidence weighted by study design and quality; see the methodology.