Vitamins & Supplements · Antioxidant
Polyphenols: Quercetin and Resveratrol
Quercetin (flavonol) and trans-resveratrol (stilbene) · also called Plant polyphenols, flavonoid supplements, quercetina, resveratrol
Quercetin and resveratrol are plant compounds found in onions, greens, berries, grape skins and peanuts, and sold as supplements. Pooled trials show a small drop in blood pressure with quercetin and a better artery test with resveratrol, but no benefit for cholesterol or inflammation, and mixed results for blood sugar. Both can interact with medicines and may interfere with cancer treatment, so ask a doctor or pharmacist first.
General information, not medical advice. Last substantive update · Not medically reviewed. A named clinician has not signed off on this page. How this page is made
About Polyphenols: Quercetin and Resveratrol
Quercetin and resveratrol are plant polyphenols sold as antioxidants. Foods supply them in small amounts; trials of capsules show small marker changes at best. Both can interact with medicines.
What they are
Quercetin is a flavonol, a type of polyphenol. Memorial Sloan Kettering (MSK) calls it the most common bioflavonoid people consume. Resveratrol is a stilbene found in grape skins and seeds, peanuts and some berries. Neither is an essential nutrient.
Both act as antioxidants in lab experiments. That does not prove they protect people when taken as capsules. NCCIH says antioxidants taken as purified chemicals might act differently from those in food, and that antioxidant supplements have not been shown to prevent cancer or heart disease.
Where they come from in food
The Linus Pauling Institute table lists quercetin per 100 g (about 3.5 oz) of raw food: rocket 66.2 mg, red onions 39.2 mg, watercress 30 mg, kale 22.6 mg, black cowpea seeds 17.2 mg, green chili peppers 14.7 mg, scallions 10.7 mg, blueberries 7.7 mg, spinach 4 mg and broccoli 3.3 mg. Brewed green tea has 2.5 mg per 100 mL.
MSK lists resveratrol sources as grape skins and seeds, peanuts, pistachios, mulberries, blueberries and cranberries. No amounts per portion were read. Food gives these compounds with many other substances, so trial results for capsules do not show what foods do.
What research shows for quercetin
Three reviews of randomised trials found quercetin lowered systolic blood pressure by about 2 to 3 mm Hg on average, with very low to moderate certainty. In young men, a 2023 review of 13 small studies found less muscle soreness after hard exercise, though all had some bias concerns. Two reviews found only a trivial-to-small effect on endurance. A 2025 review of polyphenol products, including quercetin, found lower hay fever symptom scores with low-to-very-low certainty.
What research shows for resveratrol
Pooled trials found resveratrol improved an ultrasound test of artery widening. A 2015 analysis of 10 trials found no benefit for inflammation, cholesterol, glucose or blood pressure. For type 2 diabetes, a 2014 meta-analysis found lower blood sugar markers while a 2020 Cochrane review of three small trials could not tell. In older adults, a 2024 review was mixed.
The body absorbs resveratrol but breaks it down fast: in six volunteers, unchanged resveratrol in blood stayed under 5 ng/ml after a 25 mg oral dose. The idea that resveratrol extends life comes from yeast cells; MSK says it has not been shown in humans.
Food versus pills
Almost all trial results above are for isolated supplements. Foods supply these compounds with fibre, vitamins and other plant substances. No trial read compared food with capsules. This page gives no amounts to take; if you wonder about your own needs, ask a doctor, pharmacist or dietitian.
At a glance
Traditional uses history, not proof
- Eaten as part of fruits, vegetables, tea and grapes
- Sold as antioxidant supplements for heart, exercise and allergy claims
Studied for research
- Lab antioxidant action, not shown to help people
- Blood pressure with quercetin, low certainty
- Muscle soreness and endurance with quercetin, low certainty
- Hay fever with mixed polyphenol products, low certainty
- Artery function with resveratrol, low certainty
- Cholesterol and inflammation with resveratrol, evidence against
- Blood sugar with resveratrol, mixed
- Older adults and Alzheimer's with resveratrol, mixed to very low
Main compounds
- Quercetin (usually the free aglycone)
- Rutin (sugar-bound quercetin)
- trans-Resveratrol
- Pterostilbene (a related compound)
Common forms
- Foods (onions, greens, berries, grapes, peanuts, tea)
- Capsules and tablets of quercetin
- Capsules of resveratrol, often from Japanese knotweed
Research links: 2016 review: quercetin and blood pressure (7 trials) · 2023 umbrella review: quercetin and heart and metabolic markers · 2022 review: resveratrol and artery function (17 studies) · 2015 review: resveratrol, CRP and cholesterol (10 trials) · 2020 Cochrane review: resveratrol in type 2 diabetes · 2018 review: safety of quercetin supplements · Research Library · Genes & Biomarkers Library
What it is and its history
- Accepted scientific name
- Quercetin (a flavonol) and trans-resveratrol (a stilbene): plant polyphenols
- Common names
- Quercetin (English); Quercetina (Spanish); Resveratrol (English); Resveratrol (Spanish); Plant polyphenols (English); Polifenoles (Spanish)
- Family or group
- Polyphenols. MSK says quercetin is a bioflavonoid and the most common one people consume. Resveratrol is a polyphenol found in grape skins and other foods.
- Look-alikes and adulterants
- Name: Grape seed extract and pine bark extract; Note: Different polyphenol products with their own page.; Name: Green tea catechins (EGCG); Note: Another polyphenol group with its own page.; Name: Curcumin; Note: A turmeric polyphenol with its own page.; Name: Rutin and pterostilbene; Note: Related compounds: rutin is sugar-bound quercetin; pterostilbene is a resveratrol relative.
- Sustainability and conservation
- Not assessed.
What is inside, and how it may work
What it contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.
Main compounds
| Compound | Family | Where it is concentrated | Activity studied | Level of evidence |
|---|---|---|---|---|
| Quercetin | flavonol (flavonoid) | Onions, kale, rocket, berries, tea (LPI table) Red onions 39.2 mg per 100 g; kale 22.6 mg per 100 g (LPI table). | Antioxidant in the lab; small fall in systolic blood pressure in pooled trials. 17 18 3 | Human data |
| Rutin | quercetin glycoside | Citrus bioflavonoid products Not read. | Sugar-bound form of quercetin sold without prescription in the US (LPI). 17 | Human data |
| trans-Resveratrol | stilbene | Grape skins and seeds, peanuts, pistachios, berries, Japanese knotweed (MSK) Not read. | Antioxidant and anti-inflammatory in the lab; improved an artery-widening test in pooled trials. 19 9 15 | Human data |
Mechanisms, receptors and pathways
| Target or pathway | Gene or receptor | What was found | Level |
|---|---|---|---|
| Antioxidant action | Not specified | MSK describes quercetin's phenolic group reacting with free radicals in lab experiments. NCCIH warns that purified antioxidants may act differently from food and that supplements have not prevented cancer or heart disease. 18 20 | Lab |
| Drug-metabolising enzymes | CYP3A4, CYP2C19 (quercetin, lab); CYP3A4, CYP2D6, CYP2C9, CYP1A2 (resveratrol, volunteers) | Both can change enzyme activity that clears some medicines. 18 19 | Lab and small human study |
| Blood vessel lining | Nitric oxide production (resveratrol, per MSK) | MSK says resveratrol induces nitric oxide and increases arterial blood flow in experiments; pooled trials show improved flow-mediated dilation. 19 9 | Lab and human marker |
| Sirtuins and ageing | Sirtuins (SIRT1, SIRT3, SIRT5) per MSK | The life-span effect was seen in yeast cells and has not been shown in humans. 19 | Lab |
| Oestrogen and androgen receptors | Oestrogen and androgen receptors (resveratrol) | MSK says resveratrol mimics phytoestrogens and may stimulate cancer cell growth in some experiments, while other experiments show the opposite. 19 | Lab |
Absorption, metabolism and elimination
- Absorption
- At least 70 percent of a 25 mg oral dose of labelled resveratrol was absorbed in six volunteers (study). Quercetin absorption was not read.
- Distribution
- Resveratrol and its main breakdown products were found in blood and spinal fluid in a 52-week trial.
- Metabolism
- Fast sulfate and glucuronic acid attachment in the gut and liver, plus some hydrogenation likely by gut bacteria (resveratrol).
- Elimination
- Most of an oral resveratrol dose was recovered in urine.
- Bioavailability
- Unchanged resveratrol in blood stayed under 5 ng/ml after a 25 mg oral dose; total resveratrol with metabolites had a half-life of about 9 hours.
Isolated compounds versus whole extracts
Foods bring these compounds with many other substances. NCCIH says antioxidants taken as purified chemicals might act differently from those in food. Trial results here are for isolated supplements, and no trial read compared food with pills.
Nutritional composition
Quercetin food values are from the Linus Pauling Institute Table 5 (mg per 100 g or 100 mL of raw food), read 2026-10-26. The page is dated 2016. No resveratrol per-portion values were read.
1 high certainty1 moderate certainty2 mixed findings5 low certainty1 very low certainty3 not enough evidence1 evidence against
What was looked at
The 14 benefits and uses checked for Polyphenols: Quercetin and Resveratrol, each with how strong the evidence is. Tap one to open it.
- What they are, and the lab antioxidant claimNot enough evidence
- Food sources of quercetin and resveratrolHigh certainty
- Blood pressure (quercetin)Low certainty
- Artery function (resveratrol)Low certainty
- Cholesterol, inflammation and blood pressure (resveratrol)Evidence against
- Blood sugar (resveratrol)Mixed findings
- Muscle soreness after hard exercise (quercetin)Low certainty
- Endurance exercise (quercetin)Low certainty
- Hay fever and allergic rhinitis (polyphenol products)Low certainty
- Older adults (resveratrol)Mixed findings
- Alzheimer's disease (resveratrol)Very low certainty
- Living longer (resveratrol)Not enough evidence
- Cancer (prevention or treatment)Not enough evidence
- How well the body takes them inModerate certainty
Lab markers tracked in the studies
Systolic blood pressureFlow-mediated dilation (FMD)C-reactive protein and cholesterolFasting glucose and HbA1cMuscle soreness and creatine kinaseVO2max and endurance performanceTotal nasal symptom scoreAmyloid beta 40 and brain volume
What is Polyphenols: Quercetin and Resveratrol good for?
The main studied uses and how strong the human evidence is for each. Most results are for isolated supplements in short trials, and many are blood markers, not health outcomes.
Benefits, one by one
Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.
What they are, and the lab antioxidant claim
Not enough evidenceQuercetin and resveratrol are plant polyphenols. They act as antioxidants in test tubes. That has not been shown to protect people who take them as capsules.
3 studiesQuercetin and resveratrol are plant compounds, not essential nutrient…
Studies, doses and limits
What the trials found
MSK says quercetin is a bioflavonoid that acts as an antioxidant in laboratory experiments, and that resveratrol also acts as an antioxidant. NCCIH says antioxidants taken as purified chemicals might act differently from those eaten in food, and that supplements have not been shown to prevent cancer or heart disease.
Results
The antioxidant action is a lab finding. It is not proof of a health benefit from supplements.
Effect sizes as reported
No effect sizes apply to a lab property.
Why this rating
The sources describe lab activity and general antioxidant-supplement trials of other nutrients, not trials proving a benefit for quercetin or resveratrol.
Form and dose studied
Quercetin and resveratrol are plant compounds, not essential nutrients. Forms: quercetin (often as the free aglycone), quercetin glycosides such as rutin, and trans-resveratrol.
Limits
This line rests on lab statements from health pages, not on human trials of these two compounds.
Why researchers looked
Both are sold as antioxidants, so readers ask whether the lab property means a health benefit.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Lab
Both neutralise reactive oxygen molecules in lab experiments. Whether this happens in the body after a capsule is not shown.
A proposed mechanism does not show that the effect happens in people.
Antioxidant supplements may interfere with some cancer treatments; see the Safety tab.
Food sources of quercetin and resveratrol
High certaintyQuercetin is in onions, leafy greens, berries and tea. Resveratrol is in grape skins, peanuts and some berries. Food gives mixtures, not single capsules.
3 studiesFoods supply these compounds with many other substances. Trial result…
Studies, doses and limits
What the trials found
The Linus Pauling Institute table lists quercetin per 100 g (about 3.5 oz) of raw food: rocket (arugula) 66.2 mg, red onions 39.2 mg, watercress 30 mg, kale 22.6 mg, black cowpea seeds 17.2 mg, green chili peppers 14.7 mg, scallions 10.7 mg, blueberries 7.7 mg, spinach 4 mg, broccoli 3.3 mg. Brewed green tea has 2.5 mg and brewed black tea 2.2 mg per 100 mL. MSK lists resveratrol sources as grape skins and seeds, peanuts, pistachios, mulberries, blueberries and cranberries, and Japanese knotweed (Polygonum cuspidatum) as a common supplement source. No resveratrol amounts per portion were read.
Results
Onions, leafy greens and berries are good quercetin sources by this table. Resveratrol amounts in foods were not read.
Effect sizes as reported
Amounts are in the studies table and the text, as nutrient content only.
Why this rating
High for the food lists, which come from a reference table and a hospital reference page. Content varies with variety, growing and cooking, which the sources do not quantify.
Form and dose studied
Foods supply these compounds with many other substances. Trial results here are for isolated supplements.
Who was studied
General population.
Limits
The LPI page was reviewed in 2016 and gives older database values. No resveratrol per-portion data were read.
Why researchers looked
People ask which foods carry these compounds and how food compares with pills.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Food composition
Not applicable: this is food composition.
A proposed mechanism does not show that the effect happens in people.
MSK says it is generally safe to eat foods with resveratrol. LPI says no adverse effects have been tied to high dietary intakes of flavonoids from plant foods.
Blood pressure (quercetin)
Low certaintyPooled trials found quercetin lowered systolic blood pressure by roughly 2 to 3 mm Hg. Whether that prevents heart attacks or strokes is not known.
3 studiesIsolated quercetin supplements; one review split trials at 500 mg a d…
Studies, doses and limits
What the trials found
Three reviews of randomised trials: Serban 2016 (7 trials, 587 people) found systolic -3.04 and diastolic -2.63 mm Hg; Huang 2020 (17 trials, 896 people) found systolic -3.09 and diastolic -2.86 mm Hg; the 2023 umbrella review found systolic -1.9 mm Hg with no effect on diastolic pressure, blood fats or fasting glucose.
Results
A small average fall in systolic pressure is seen in pooled trials. The size is modest and the trials differ a lot.
Effect sizes as reported
Systolic -1.9 to -3.1 mm Hg across the three reviews.
Why this rating
Low: results are consistent in direction, but the umbrella review rates certainty very low to moderate, differences between trials are large (I2 88 percent) and blood pressure is a marker, not a heart outcome.
Form and dose studied
Isolated quercetin supplements; one review split trials at 500 mg a day and found no significant difference between the two groups.
Who was studied
Mostly adults with raised blood pressure or metabolic problems, and some healthy adults.
Limits
Small trials, short follow-up; no trial of heart attacks or strokes was read. Authors say clinical meaning is unknown.
Why researchers looked
Quercetin is sold for heart health, and several small trials measured blood pressure.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Not established
Not established. Lab work suggests effects on blood vessels, but that was not tested in these reviews.
A proposed mechanism does not show that the effect happens in people.
Quercetin may change how some medicines are processed; see the Safety tab.
Artery function (resveratrol)
Low certaintyResveratrol improved an ultrasound test of how well arteries widen. That is a marker, not proof of fewer heart problems.
3 studiesResveratrol supplements; amounts varied by trial.
Studies, doses and limits
What the trials found
Mohammadipoor 2022 (17 studies) found flow-mediated dilation up by 1.43 percentage points and ICAM-1 down; VCAM-1, fibrinogen and PAI-1 did not change. Akbari 2019 (28 trials in metabolic syndrome and related disorders) also found higher flow-mediated dilation but no change in blood pressure.
Results
One artery-widening test improved in pooled trials. Other markers and blood pressure did not.
Effect sizes as reported
FMD +1.43 percentage points (0.98 to 1.88); SMD 1.77 in metabolic syndrome (0.25 to 3.29).
Why this rating
Low: it is a marker, differences between trials are extreme (I2 96.5 percent in one review) and the abstracts give no certainty rating.
Form and dose studied
Resveratrol supplements; amounts varied by trial.
Who was studied
Healthy adults and people with metabolic syndrome or related conditions.
Limits
Marker only; no heart-event outcomes; high heterogeneity.
Why researchers looked
Resveratrol is linked in the media to wine and heart health, so reviews tested artery-function markers.
Traditional use
Resveratrol is a plant stilbene found in grape skins. MSK says the life-extension idea comes from yeast cells and is not shown in humans.
Proposed mechanism Preliminary mechanism
Not established in people. Lab work suggests resveratrol raises nitric oxide, which relaxes arteries (MSK).
A proposed mechanism does not show that the effect happens in people.
Resveratrol may raise bleeding risk with blood thinners; see the Safety tab.
Cholesterol, inflammation and blood pressure (resveratrol)
Evidence againstA pooled analysis of 10 trials found no benefit of resveratrol on inflammation, cholesterol, glucose or blood pressure.
2 studiesResveratrol supplements; amounts varied by trial.
Studies, doses and limits
What the trials found
Sahebkar 2015 (10 trials) found no change in C-reactive protein, total or LDL cholesterol, triglycerides, glucose or blood pressure. HDL cholesterol was slightly lower with resveratrol (-4.18 mg/dL). Akbari 2019 also found no change in blood pressure.
Results
No benefit was found on these risk factors.
Effect sizes as reported
CRP -0.144 mg/L (-0.968 to 0.680); LDL -0.31 mg/dL; systolic +0.82 mm Hg; HDL -4.18 mg/dL (-6.54 to -1.82).
Why this rating
Against: a pooled analysis of 10 randomised trials found no effect, and the authors' own conclusion is lack of efficacy. The review is from 2015, so newer trials are not included.
Form and dose studied
Resveratrol supplements; amounts varied by trial.
Who was studied
Adults in randomised trials.
Limits
Search ended in 2014; larger trials were called for by the authors.
Why researchers looked
Resveratrol is marketed for heart protection.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism None stated
Not applicable: this is a null result.
A proposed mechanism does not show that the effect happens in people.
Not a safety finding, but the small HDL fall was in the wrong direction.
Blood sugar (resveratrol)
Mixed findingsSome pooled trials found lower blood sugar in people with diabetes. A Cochrane review of three small trials could not tell either way.
4 studiesOral resveratrol; amounts in the Cochrane trials were 10 mg, 150 mg a…
Studies, doses and limits
What the trials found
Liu 2014 (11 trials, 388 people) found lower fasting glucose, insulin, HbA1c and insulin resistance in people with diabetes but no change in people without diabetes. The 2020 Cochrane review found only 3 trials (50 adults, 4 to 5 weeks) with neutral results on HbA1c, fasting glucose and insulin resistance, and rated the evidence very low. Sahebkar 2015 found no change in glucose.
Results
Results are mixed. A positive older meta-analysis, and a Cochrane review that says the research is insufficient.
Effect sizes as reported
Liu 2014: lower in diabetes, numbers not in the abstract. Cochrane: HbA1c MD 0.1 percent (-0.02 to 0.2); fasting glucose MD 2 mg/dL (-2 to 7).
Why this rating
Mixed: the pooled analysis and the Cochrane review point in different directions, and the Cochrane trials were tiny and short.
Form and dose studied
Oral resveratrol; amounts in the Cochrane trials were 10 mg, 150 mg and 1,000 mg a day (studied in trials).
Who was studied
Adults with type 2 diabetes; no effect in people without diabetes.
Limits
Short trials; no long-term outcomes; people on diabetes medicines should not add supplements without asking their doctor.
Why researchers looked
Resveratrol has been tested in type 2 diabetes because of lab and animal findings.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Hypothesis
Not established in people.
A proposed mechanism does not show that the effect happens in people.
Ask a doctor or pharmacist before adding any supplement to diabetes medicines.
Muscle soreness after hard exercise (quercetin)
Low certaintyA pooled analysis of 13 small studies found less soreness and lower creatine kinase after hard exercise, mostly in young men.
2 studiesQuercetin supplements at about 1,000 mg a day for 1 to 12 weeks (stud…
Studies, doses and limits
What the trials found
Rojano-Ortega 2023 (13 studies, 249 people; all but one used 1,000 mg a day, for up to 12 weeks) found lower soreness 0 to 24 hours after exercise (SMD -1.33), lower creatine kinase at 24 to 48 hours (SMD -1.15) and lower oxidative stress (SMD -0.92). IL-6 did not change. All studies had some concerns about bias.
Results
Less muscle soreness and muscle-damage marker in small, short studies.
Effect sizes as reported
Soreness SMD -1.33; creatine kinase SMD -1.15; oxidative stress SMD -0.92.
Why this rating
Low: every included study had some risk-of-bias concerns, and the studies were small and short.
Form and dose studied
Quercetin supplements at about 1,000 mg a day for 1 to 12 weeks (studied in trials).
Who was studied
Young men, sedentary to well-trained.
Limits
Women and older adults were not the focus; long-term use not studied.
Why researchers looked
Athletes use quercetin to recover from hard training.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Hypothesis
Not established in people.
A proposed mechanism does not show that the effect happens in people.
Long-term safety of 1,000 mg or more a day is not established (Andres 2018).
Endurance exercise (quercetin)
Low certaintyTwo pooled analyses found only a trivial-to-small effect on endurance, and one concluded quercetin is unlikely to help.
2 studiesQuercetin at about 1,000 mg a day for a median 11 days (studied in tr…
Studies, doses and limits
What the trials found
Kressler 2011 (11 studies, 254 people) found about 2 percent better endurance capacity (effect size 0.15). Pelletier 2013 (7 studies, 288 people) found 0.74 percent better endurance performance, only in untrained people, and 1.94 percent higher VO2max, and judged the effect likely trivial.
Results
Very small gain on average; not in trained people.
Effect sizes as reported
Effect size 0.15 (about 2 percent); endurance +0.74 percent; VO2max +1.94 percent.
Why this rating
Low: tiny effects, short studies and large differences between studies.
Form and dose studied
Quercetin at about 1,000 mg a day for a median 11 days (studied in trials).
Who was studied
Mostly young adults, trained and untrained.
Limits
Short studies; benefit not seen in trained people in one analysis.
Why researchers looked
Quercetin is marketed to athletes for endurance.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Hypothesis
Not established.
A proposed mechanism does not show that the effect happens in people.
See the Safety tab.
Hay fever and allergic rhinitis (polyphenol products)
Low certaintyPooled trials of polyphenol products, including quercetin, found lower nose symptom scores. The evidence is low to very low and not specific to quercetin.
2 studiesMixed polyphenol products (catechins, quercetin and others); not quer…
Studies, doses and limits
What the trials found
Lai 2025 (13 trials, 823 people) found lower total nasal symptom scores (SMD 0.73), sneezing and nasal itching with polyphenol products such as catechins or quercetin. Quality of life did not change significantly. The authors rate certainty as low to very low.
Results
Some symptom improvement across mixed polyphenol products; not proof for quercetin alone.
Effect sizes as reported
Total nasal symptom score SMD 0.73 (combined analysis).
Why this rating
Low: low-to-very-low certainty by the authors, different products pooled together.
Form and dose studied
Mixed polyphenol products (catechins, quercetin and others); not quercetin alone.
Who was studied
Adults and children with seasonal or year-round allergic rhinitis.
Limits
Products differ; no quercetin-only pooled result was read.
Why researchers looked
Quercetin is sold for allergies because of lab findings on histamine release.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Lab
MSK says laboratory studies show quercetin inhibits histamine release; clinical trials were not described there.
A proposed mechanism does not show that the effect happens in people.
Antihistamine and allergy medicines were not checked for interactions in these sources.
Older adults (resveratrol)
Mixed findingsA review of 10 trials in older adults was mixed: some gains with exercise, no gain in diabetes or leg artery disease, and a few heart-risk markers rose at high doses.
2 studiesResveratrol supplements, some combined with exercise.
Studies, doses and limits
What the trials found
Yadegar 2024 (10 randomised trials) found resveratrol with exercise improved exercise adaptation and muscle function in healthy older adults and mobility in people with functional limits. In overweight people it helped thinking but raised some heart-risk markers at high doses. In older adults with diabetes or peripheral artery disease it was no better than placebo. No study reported significant adverse events.
Results
Mixed, small trials; no clear overall benefit.
Effect sizes as reported
Not a pooled number.
Why this rating
Mixed: gains in some groups, none in others, few trials, and the authors say amounts and long-term effects are unknown.
Form and dose studied
Resveratrol supplements, some combined with exercise.
Who was studied
Older adults, healthy and with long-term conditions.
Limits
Few varied trials; the best amount is unknown.
Why researchers looked
Resveratrol is marketed for ageing.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Hypothesis
Not established.
A proposed mechanism does not show that the effect happens in people.
High amounts raised some heart-risk markers in one group.
Alzheimer's disease (resveratrol)
Very low certaintyOne 52-week trial in 119 people found resveratrol reached the brain and changed some biomarkers, but brain volume loss was greater, and the abstract reports no clinical benefit.
3 studiesResveratrol stepped up to 1,000 mg twice a day (studied in the trial).
Studies, doses and limits
What the trials found
Turner 2015 (phase II, 119 people with mild to moderate Alzheimer's) found resveratrol and its breakdown products in blood and spinal fluid. Blood and spinal fluid amyloid beta 40 fell less with resveratrol than with placebo, and brain volume loss was greater with resveratrol. The most common side effects were nausea, diarrhoea and weight loss. MSK also reports a meta-analysis that found no effect on memory or thinking.
Results
Biomarkers changed, but the meaning is unclear and no clinical improvement was reported in the abstract.
Effect sizes as reported
Directions only; numbers not in the abstract.
Why this rating
Very low: one trial, biomarker outcomes whose meaning is unclear, and greater brain volume loss with resveratrol.
Form and dose studied
Resveratrol stepped up to 1,000 mg twice a day (studied in the trial).
Who was studied
People with mild to moderate Alzheimer's disease.
Limits
A single trial; the authors say biomarker changes need further study.
Why researchers looked
Resveratrol was tested in Alzheimer's because of lab studies.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Hypothesis
Not established.
A proposed mechanism does not show that the effect happens in people.
Greater brain volume loss and weight loss were seen; see the Safety tab.
Living longer (resveratrol)
Not enough evidenceThe idea that resveratrol extends life comes from yeast cells. MSK says it has not been shown in humans.
2 studiesNot applicable.
Studies, doses and limits
What the trials found
MSK states that resveratrol prolongs the life span of yeast cells and that this effect has not yet been demonstrated in humans. MSK also says resveratrol does not decrease the risk of death from any cause in older adults, citing a study it lists.
Results
No human evidence that it lengthens life.
Why this rating
Insufficient: only a lab finding in yeast, plus a hospital summary of human data. We did not open the study MSK cites on death risk.
Limits
Human data read are limited to the MSK summary.
Why researchers looked
Resveratrol is marketed as an anti-ageing supplement.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Lab
In yeast, resveratrol activates sirtuins (MSK); this is not shown in humans.
A proposed mechanism does not show that the effect happens in people.
None specific.
Cancer (prevention or treatment)
Not enough evidenceBoth compounds slow cancer cells in the lab. MSK says quercetin has not been shown to treat cancer, and human data for resveratrol are very limited.
3 studiesNot applicable.
Studies, doses and limits
What the trials found
MSK: quercetin has not been shown to treat cancer or other diseases, and a systematic review it cites showed no reduction in ovarian cancer risk. For resveratrol, MSK says data in cancer patients are very limited, and a high-dose micronized resveratrol study in people with multiple myeloma was stopped because of serious adverse events including kidney failure. We did not read that original study's abstract.
Results
No human evidence of cancer prevention or treatment; possible harm in one stopped study.
Why this rating
Insufficient: mostly lab data; the one human study mentioned by MSK was stopped for safety.
Who was studied
People with cancer or at risk.
Limits
Original myeloma study abstract was not available to read.
Why researchers looked
Lab results led to cancer research.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Lab
Lab work only; both compounds are antioxidants and affect cell signalling in test tubes.
A proposed mechanism does not show that the effect happens in people.
Antioxidant supplements may interfere with chemotherapy; resveratrol has oestrogen-like activity. See the Safety tab.
How well the body takes them in
Moderate certaintyResveratrol is absorbed but the body breaks it down so fast that almost none stays in its original form in the blood.
1 studiesSingle 25 mg oral dose (studied in the trial).
Studies, doses and limits
What the trials found
Walle 2004 gave six volunteers a 25 mg oral dose of labelled resveratrol. At least 70 percent was absorbed, but unchanged resveratrol in blood stayed under 5 ng/ml. Total resveratrol plus metabolites peaked at about 2 micromolar with a half-life of about 9 hours. Quercetin absorption was not read from a source here.
Results
Very little resveratrol reaches the blood unchanged.
Effect sizes as reported
Peak 491 ng/ml with metabolites; unchanged under 5 ng/ml.
Why this rating
Moderate: a careful six-person tracer study, but small and from 2004, and it shows what the body does, not what it does for health.
Form and dose studied
Single 25 mg oral dose (studied in the trial).
Who was studied
Six healthy volunteers.
Limits
Six people; one dose.
Why researchers looked
Weak blood levels may explain why trials give modest results.
Traditional use
Quercetin and resveratrol are plant compounds, not essential nutrients. Lab activity is different from showing that a supplement treats a condition.
Proposed mechanism Human tracer studies
Gut and liver add sulfate and glucuronic acid to resveratrol (human tracer study).
A proposed mechanism does not show that the effect happens in people.
None specific.
Connections to the rest of health
How Polyphenols: Quercetin and Resveratrol connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.
Explore every connection: goals, body systems, organs, symptoms, genes
A. Wellness goals
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Cellular Protection | Not enough evidence | What they are, and the lab antioxidant claim: Quercetin and resveratrol are plant polyphenols. They act as antioxidants in test tubes. That has not been shown to protect people who take them as capsules. | 18 19 20 | |
| Preventive Wellness | Not enough evidence | What they are, and the lab antioxidant claim: Quercetin and resveratrol are plant polyphenols. They act as antioxidants in test tubes. That has not been shown to protect people who take them as capsules. | 18 19 20 | |
| Balanced Nutrition | High certainty | Food sources of quercetin and resveratrol: Quercetin is in onions, leafy greens, berries and tea. Resveratrol is in grape skins, peanuts and some berries. Food gives mixtures, not single capsules. | 17 19 20 | |
| Blood Pressure Support | Low certainty | Blood pressure (quercetin): Pooled trials found quercetin lowered systolic blood pressure by roughly 2 to 3 mm Hg. Whether that prevents heart attacks or strokes is not known. | 13 3 4 | |
| Heart Health | Low certainty | Blood pressure (quercetin): Pooled trials found quercetin lowered systolic blood pressure by roughly 2 to 3 mm Hg. Whether that prevents heart attacks or strokes is not known. Artery function (resveratrol): Resveratrol improved an ultrasound test of how well arteries widen. That is a marker, not proof of fewer heart problems. | 13 3 4 9 1 19 | |
| Cholesterol Balance | Evidence against | Cholesterol, inflammation and blood pressure (resveratrol): A pooled analysis of 10 trials found no benefit of resveratrol on inflammation, cholesterol, glucose or blood pressure. | 12 1 | |
| Heart Health | Evidence against | Cholesterol, inflammation and blood pressure (resveratrol): A pooled analysis of 10 trials found no benefit of resveratrol on inflammation, cholesterol, glucose or blood pressure. | 12 1 | |
| Blood Sugar Balance | Mixed findings | Blood sugar (resveratrol): Some pooled trials found lower blood sugar in people with diabetes. A Cochrane review of three small trials could not tell either way. | 8 5 12 19 | |
| Metabolic Health | Mixed findings | Blood sugar (resveratrol): Some pooled trials found lower blood sugar in people with diabetes. A Cochrane review of three small trials could not tell either way. | 8 5 12 19 | |
| Muscle Recovery | Low certainty | Muscle soreness after hard exercise (quercetin): A pooled analysis of 13 small studies found less soreness and lower creatine kinase after hard exercise, mostly in young men. | 11 2 | |
| Sports Performance | Low certainty | Muscle soreness after hard exercise (quercetin): A pooled analysis of 13 small studies found less soreness and lower creatine kinase after hard exercise, mostly in young men. Endurance exercise (quercetin): Two pooled analyses found only a trivial-to-small effect on endurance, and one concluded quercetin is unlikely to help. | 11 2 6 10 | |
| Endurance Support | Low certainty | Endurance exercise (quercetin): Two pooled analyses found only a trivial-to-small effect on endurance, and one concluded quercetin is unlikely to help. | 6 10 | |
| Immune Support | Low certainty | Hay fever and allergic rhinitis (polyphenol products): Pooled trials of polyphenol products, including quercetin, found lower nose symptom scores. The evidence is low to very low and not specific to quercetin. | 7 18 | |
| Healthy Aging | Mixed findings | Older adults (resveratrol): A review of 10 trials in older adults was mixed: some gains with exercise, no gain in diabetes or leg artery disease, and a few heart-risk markers rose at high doses. | 16 19 | |
| Physical Stamina | Mixed findings | Older adults (resveratrol): A review of 10 trials in older adults was mixed: some gains with exercise, no gain in diabetes or leg artery disease, and a few heart-risk markers rose at high doses. | 16 19 | |
| Brain Health | Very low certainty | Alzheimer's disease (resveratrol): One 52-week trial in 119 people found resveratrol reached the brain and changed some biomarkers, but brain volume loss was greater, and the abstract reports no clinical benefit. | 14 16 19 | |
| Memory Support | Very low certainty | Alzheimer's disease (resveratrol): One 52-week trial in 119 people found resveratrol reached the brain and changed some biomarkers, but brain volume loss was greater, and the abstract reports no clinical benefit. | 14 16 19 | |
| Longevity | Not enough evidence | Living longer (resveratrol): The idea that resveratrol extends life comes from yeast cells. MSK says it has not been shown in humans. | 19 16 | |
| Healthy Aging | Not enough evidence | Living longer (resveratrol): The idea that resveratrol extends life comes from yeast cells. MSK says it has not been shown in humans. | 19 16 | |
| Preventive Wellness | Not enough evidence | Cancer (prevention or treatment): Both compounds slow cancer cells in the lab. MSK says quercetin has not been shown to treat cancer, and human data for resveratrol are very limited. | 18 19 20 | |
| Balanced Nutrition | Moderate certainty | How well the body takes them in: Resveratrol is absorbed but the body breaks it down so fast that almost none stays in its original form in the blood. | 15 |
B. Body systems
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Whole Body | Biological association | Not enough evidence | Studied for: What they are, and the lab antioxidant claim Studied for: Older adults (resveratrol) | 18 19 20 16 |
| Nutrition | Biological association | High certainty | Studied for: Food sources of quercetin and resveratrol | 17 19 20 |
| Cardiovascular System | Biological association | Low certainty | Studied for: Blood pressure (quercetin) Studied for: Artery function (resveratrol) | 13 3 4 9 1 19 12 |
| Heart Circulation | Biological association | Low certainty | Studied for: Artery function (resveratrol) | 9 1 19 |
| Blood Sugar Support | Biological association | Mixed findings | Studied for: Blood sugar (resveratrol) | 8 5 12 19 |
| Endocrine System | Biological association | Mixed findings | Studied for: Blood sugar (resveratrol) | 8 5 12 19 |
| Musculoskeletal System | Biological association | Low certainty | Studied for: Muscle soreness after hard exercise (quercetin) Studied for: Endurance exercise (quercetin) | 11 2 6 10 16 19 |
| Respiratory System | Biological association | Low certainty | Studied for: Hay fever and allergic rhinitis (polyphenol products) | 7 18 |
| Immune System | Biological association | Low certainty | Studied for: Hay fever and allergic rhinitis (polyphenol products) | 7 18 |
| Nervous System | Biological association | Very low certainty | Studied for: Alzheimer's disease (resveratrol) | 14 16 19 |
| Metabolism | Biological association | Moderate certainty | Studied for: How well the body takes them in | 15 |
E. Health conditions
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| High blood pressure | Preliminary | Small average fall in systolic blood pressure in pooled trials. Small average fall in systolic blood pressure with quercetin in pooled trials. Preparation or compound: Quercetin supplements |
13 4 3 | |
| Type 2 diabetes | Mixed findings | A positive pooled analysis and a neutral Cochrane review. Preparation or compound: Resveratrol supplements |
8 5 | |
| Alzheimer's disease | Adverse effect or risk | Randomised trial | Greater brain volume loss than placebo in a 52-week trial. Preparation or compound: Resveratrol |
14 |
I. Biomarkers
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Systolic blood pressure | Biological association | Low certainty | Measured in trials: lower (small). A lab change is not the same as a health benefit. | 13 4 3 |
| Flow-mediated dilation (FMD) | Biological association | Low certainty | Measured in trials: higher. A lab change is not the same as a health benefit. | 9 1 |
| C-reactive protein and cholesterol | Biological association | Evidence against | Measured in trials: no change (HDL slightly lower). A lab change is not the same as a health benefit. | 12 |
| Fasting glucose and HbA1c | Biological association | Mixed findings | Measured in trials: lower in one meta-analysis; neutral in the Cochrane review. A lab change is not the same as a health benefit. | 8 5 |
| Muscle soreness and creatine kinase | Biological association | Low certainty | Measured in trials: lower. A lab change is not the same as a health benefit. | 11 |
| VO2max and endurance performance | Biological association | Low certainty | Measured in trials: slightly higher. A lab change is not the same as a health benefit. | 6 10 |
| Total nasal symptom score | Biological association | Low certainty | Measured in trials: lower. A lab change is not the same as a health benefit. | 7 |
| Amyloid beta 40 and brain volume | Biological association | Very low certainty | Measured in trials: amyloid beta 40 fell less; brain volume loss greater. A lab change is not the same as a health benefit. | 14 |
J. Genes, receptors and enzymes
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| CYP3A4 | Preliminary mechanism | Lab and small human study | Inhibited by quercetin in the lab and by resveratrol in volunteers (MSK). | 18 19 |
| SIRT1 | Preliminary mechanism | Lab | Linked to the yeast life-span result for resveratrol; not shown in humans. | 19 |
L. Active compounds
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Quercetin | Biological association | Human | Antioxidant in the lab; small fall in systolic blood pressure in pooled trials. Preparation or compound: Onions, kale, rocket, berries, tea (LPI table) |
17 18 3 |
| Rutin | Biological association | Human | Sugar-bound form of quercetin sold without prescription in the US (LPI). Preparation or compound: Citrus bioflavonoid products |
17 |
| trans-Resveratrol | Biological association | Human | Antioxidant and anti-inflammatory in the lab; improved an artery-widening test in pooled trials. Preparation or compound: Grape skins and seeds, peanuts, pistachios, berries, Japanese knotweed (MSK) |
19 9 15 |
Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 26, 2026).
Evidence at a glance: what the research found for 14 outcomes
Each outcome below is one thing researchers measured. Certainty is how far the evidence can be trusted, not how well it works. The full studies are on the next tab.
The evidence
The research centre for Polyphenols: Quercetin and Resveratrol. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.
Evidence by outcome
Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).
How we rate evidence
High certainty
Several well-run trials or reviews agree; further research is unlikely to change the picture much.
Moderate certainty
Good trials point the same way, but some doubt remains.
Low certainty
Small, short or inconsistent trials. The finding could change with better research.
Very low certainty
Very little or very weak human data. Treat as a possibility only.
Mixed findings
Trials or reviews disagree with each other.
Not enough evidence
Not enough human research to say either way.
Evidence against
Good research found no benefit, or found harm.
We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We started from our existing summary, read the MSK, NCCIH and Linus Pauling Institute pages in full, and re-read PubMed abstracts for 16 reviews and trials. Only abstracts were read for studies. Some pages (LactMed, LiverTox, NIH Office of Dietary Supplements) could not be opened and are marked unread.
Study library: every study we checked 20
| Study | Design | People | Product, dose, length | Result |
|---|---|---|---|---|
| Akbari 2019 The Effects of Resveratrol Supplementation on Endothelial Function and Blood Pressures Among Patients with Metabolic Syndrome and Related Disorders: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. High Blood Press Cardiovasc Prev · PMID 31264084 · DOI |
Systematic review meta analysis |
28 randomised trials (33 findings) in people with metabolic syndrome and related disorders; searched to October 2018 | Resveratrol supplements Capsule or tablet Varied by trial Varied by trial · vs Placebo or control |
Resveratrol raised flow-mediated dilation. It did not significantly change systolic or diastolic blood pressure. FMD SMD 1.77; systolic SMD -0.27; diastolic SMD -0.21 (FMD 0.25 to 3.29 (I2 96.5%); systolic -0.57 to 0.03; diastolic -0.52 to 0.11) Methods, limits and fundingOutcomes: Flow-mediated dilation, systolic and diastolic blood pressure Limitations: Extremely large differences between trials (I2 near 90 to 97 percent). The authors suggest higher doses and longer trials. Funding and conflicts: Funding not stated in the abstract. Read: abstract |
| Andres 2018 Safety Aspects of the Use of Quercetin as a Dietary Supplement. Mol Nutr Food Res · PMID 29127724 · DOI |
Narrative review |
Review of human intervention studies, animal studies and drug-interaction studies of isolated quercetin | Isolated quercetin, mostly as the free aglycone Supplement |
Adverse effects in human studies were rarely reported and mild. Adequate data on long-term use (more than 12 weeks) of high amounts (1,000 mg or more) are not available. Animal studies suggest quercetin could worsen kidney damage that is already there, and could promote tumours that depend on oestrogen. Short-term studies in animals and people show quercetin can change how much of some medicines the body takes in. No numbers in the abstract (Not applicable) Methods, limits and fundingOutcomes: Adverse effects, long-term safety, kidney, cancer, drug interactions Limitations: A narrative review read from the abstract only; the animal findings may not carry over to people. Funding and conflicts: Authors are from a German federal risk-assessment institute; no conflict is stated in the abstract. Read: abstract |
| Arabi 2023 The effects of Quercetin supplementation on cardiometabolic outcomes: An umbrella review of meta-analyses of randomized controlled trials. Phytother Res · PMID 37654199 · DOI |
Umbrella review |
5 meta-analyses covering 18 randomised trials, plus 5 newer trials | Quercetin supplements Capsule or tablet Varied by trial Varied by trial · vs Placebo |
Quercetin lowered systolic blood pressure and insulin level a little. It did not change diastolic pressure, blood fats, inflammation markers, body measures, fasting glucose or insulin resistance. The authors rate the certainty of evidence as very low to moderate. Systolic WMD -1.9 mm Hg; insulin WMD -1.07 (Systolic -3.2 to -0.6 (I2 88.3%); insulin -1.9 to -0.1 (I2 75.0%)) Methods, limits and fundingOutcomes: Blood pressure, blood fats, inflammation, body measures, fasting glucose, insulin Limitations: Very large differences between trials (I2 above 75%); abstract does not say how the certainty varied by outcome. Funding and conflicts: Funding not stated in the abstract. Read: abstract |
| Huang 2020 Effect of quercetin supplementation on plasma lipid profiles, blood pressure, and glucose levels: a systematic review and meta-analysis. Nutr Rev · PMID 31940027 · DOI |
Systematic review meta analysis |
896 17 randomised trials, 896 people; searched to July 2018 |
Quercetin or a standardised quercetin-enriched extract Capsule, tablet or extract Varied by trial Varied by trial; subgroup of 8 weeks or longer · vs Placebo or control |
Quercetin lowered systolic and diastolic blood pressure. Overall, blood fats and glucose did not change. In trials of 8 weeks or longer with a parallel design, HDL cholesterol and triglycerides changed. Systolic WMD -3.09 mm Hg; diastolic WMD -2.86 mm Hg (Systolic -4.59 to -1.59; diastolic -5.09 to -0.63) Methods, limits and fundingOutcomes: Blood fats, blood pressure, glucose Limitations: Subgroup findings on blood fats come from a smaller set of trials; blood pressure is a marker only. Funding and conflicts: Funding not stated in the abstract. Read: abstract |
| Jeyaraman 2020 Resveratrol for adults with type 2 diabetes mellitus. Cochrane Database Syst Rev · PMID 31978258 · DOI |
Systematic review meta analysis |
50 3 randomised trials, 50 adults with type 2 diabetes; low risk of bias; last search December 2018 |
Oral resveratrol (not combined with other plant polyphenols) Oral supplement 10 mg, 150 mg or 1,000 mg a day (studied in trials) 4 to 5 weeks · vs Placebo |
Resveratrol had neutral effects on HbA1c, fasting glucose and insulin resistance (very low certainty). No trial reported long-term outcomes such as complications or deaths. The trials reported no adverse events, but that evidence is also very low quality. The authors say research is insufficient to judge benefit or harm. HbA1c MD 0.1 percent; fasting glucose MD 2 mg/dL; insulin resistance MD -0.35 (HbA1c -0.02 to 0.2; glucose -2 to 7; insulin resistance -0.99 to 0.28) Methods, limits and fundingOutcomes: HbA1c, fasting glucose, insulin resistance, adverse events, long-term outcomes Limitations: Very small and short trials; 8 ongoing trials with about 800 people were not yet included. Funding and conflicts: Cochrane review; authors declare no known conflicts of interest in the record. Read: abstract |
| Kressler 2011 Quercetin and endurance exercise capacity: a systematic review and meta-analysis. Med Sci Sports Exerc · PMID 21606866 · DOI |
Systematic review meta analysis |
254 11 studies, 254 people (starting VO2max 41 to 64 mL/kg/min) |
Quercetin supplements Capsule or tablet Median 1,000 mg a day (studied in trials) Median 11 days · vs Placebo |
Quercetin gave a statistically significant but trivial-to-small benefit in endurance capacity, about 2 percent better than placebo. Effect size 0.15 (about 2 percent) (0.02 to 0.27) Methods, limits and fundingOutcomes: Endurance exercise capacity (VO2max and endurance performance) Limitations: Small effect; large differences between studies that the authors could not explain. An erratum and a comment exist for this paper. Funding and conflicts: Funding not stated in the abstract. Read: abstract |
| Lai 2025 Clinical Effects of Polyphenolic Compounds on Allergic Rhinitis: A Systematic Review and Meta-Analysis. J Allergy Clin Immunol Pract · PMID 40618891 · DOI |
Systematic review meta analysis |
823 13 randomised trials, 823 people with hay fever (7 seasonal, 6 year-round allergic rhinitis) |
Mixed polyphenol products (for example catechins or quercetin); not quercetin alone Varied by trial Varied by trial Varied by trial · vs Placebo or control |
Polyphenol products lowered total nasal symptom scores, sneezing and nasal itching in seasonal allergic rhinitis. Quality of life did not change significantly. The authors rate the certainty of evidence as low to very low and ask for larger trials. Total nasal symptom score SMD 0.73 (combined analysis) (P < .0001 (confidence interval not given in the abstract)) Methods, limits and fundingOutcomes: Total nasal symptom score, sneezing, nasal itching, nasal obstruction, quality of life Limitations: The products were different polyphenols, so this does not show what quercetin alone does. Low to very low certainty. Funding and conflicts: Funding not stated in the abstract. Read: abstract |
| Liu 2014 Effect of resveratrol on glucose control and insulin sensitivity: a meta-analysis of 11 randomized controlled trials. Am J Clin Nutr · PMID 24695890 · DOI |
Systematic review meta analysis |
388 11 randomised trials, 388 people (people with and without diabetes) |
Resveratrol supplements Capsule or tablet Varied by trial Varied by trial · vs Placebo or control |
In people with diabetes, resveratrol lowered fasting glucose, insulin, HbA1c and insulin resistance. In people without diabetes it did not change these measures. Directions only; numbers are not in the abstract (Not given in the abstract) Methods, limits and fundingOutcomes: Fasting glucose, insulin, HbA1c, insulin resistance (HOMA) Limitations: Older review (searched to March 2014); the authors call for more high-quality studies; a later Cochrane review found only 3 small trials in diabetes and could not tell. Funding and conflicts: Funding not stated in the abstract (PubMed lists non-US government research support). Read: abstract |
| Mohammadipoor 2022 Resveratrol supplementation efficiently improves endothelial health: A systematic review and meta-analysis of randomized controlled trials. Phytother Res · PMID 35833325 · DOI |
Systematic review meta analysis |
17 randomised studies (21 arms); searched to February 2021 | Resveratrol supplements Capsule or tablet Varied by trial Varied by trial · vs Placebo or control |
Resveratrol raised flow-mediated dilation (an ultrasound test of how well an artery widens) and lowered ICAM-1, a blood marker. VCAM-1, fibrinogen and PAI-1 did not change. FMD WMD +1.43 percentage points; ICAM-1 WMD -7.09 ng/ml (FMD 0.98 to 1.88; ICAM-1 -7.45 to -6.73) Methods, limits and fundingOutcomes: Flow-mediated dilation (FMD), ICAM-1, VCAM-1, fibrinogen, PAI-1 Limitations: These are marker results, not fewer heart attacks or strokes. The abstract gives no certainty rating. Funding and conflicts: Funding not stated in the abstract. Read: abstract |
| Pelletier 2013 Effects of quercetin supplementation on endurance performance and maximal oxygen consumption: a meta-analysis. Int J Sport Nutr Exerc Metab · PMID 22805526 · DOI |
Systematic review meta analysis |
288 7 articles, 288 people |
Quercetin supplements Capsule or tablet About 960 to 1,000 mg a day (studied in trials) Averages of 8 to 26 days · vs Placebo |
Quercetin raised endurance performance by 0.74 percent overall, but only in untrained people (0.83 percent); there was no clear gain in trained people. VO2max rose by 1.94 percent. The authors conclude the effect is likely trivial and that quercetin is unlikely to help endurance exercise. Endurance performance +0.74 percent; VO2max +1.94 percent (Endurance 0.10 to 1.39; VO2max 0.30 to 3.59) Methods, limits and fundingOutcomes: Endurance performance (power output) and VO2max Limitations: Short studies; trivial effect size by the authors' own judgement. Funding and conflicts: Funding not stated in the abstract. Read: abstract |
| Rojano-Ortega 2023 Quercetin supplementation promotes recovery after exercise-induced muscle damage: a systematic review and meta-analysis of randomized controlled trials. Biol Sport · PMID 37398956 · DOI |
Systematic review meta analysis |
249 13 studies, 249 sedentary to well-trained participants; the conclusion refers to young men |
Quercetin supplements Capsule or tablet All but one study used 1,000 mg a day (studied in trials) More than 7 days and up to 12 weeks · vs Placebo |
Quercetin sped up recovery of muscle function and lowered soreness (0 to 24 hours after exercise), creatine kinase (24 to 48 hours) and a measure of oxidative stress. It had no effect on IL-6. Soreness SMD -1.33; creatine kinase SMD -1.15; oxidative stress SMD -0.92 (Not given in the abstract (p = 0.03, 0.02 and 0.03)) Methods, limits and fundingOutcomes: Muscle soreness, creatine kinase, oxidative stress, IL-6 after hard exercise Limitations: All 13 studies had some concerns about risk of bias; mostly young men; short follow-up. Funding and conflicts: The authors declare no conflict of interest. Read: abstract |
| Sahebkar 2015 Lack of efficacy of resveratrol on C-reactive protein and selected cardiovascular risk factors--Results from a systematic review and meta-analysis of randomized controlled trials. Int J Cardiol · PMID 25885871 · DOI |
Systematic review meta analysis |
10 randomised trials (11 treatment arms); searched to August 2014 | Resveratrol supplements Capsule or tablet Varied by trial Varied by trial · vs Placebo |
Resveratrol did not change C-reactive protein, total or LDL cholesterol, triglycerides, glucose or blood pressure. It slightly lowered HDL cholesterol. The authors conclude it does not suggest any benefit for these risk factors. CRP WMD -0.144 mg/L; HDL WMD -4.18 mg/dL (CRP -0.968 to 0.680; HDL -6.54 to -1.82) Methods, limits and fundingOutcomes: C-reactive protein, cholesterol, triglycerides, glucose, blood pressure Limitations: Searched only to 2014; larger well-designed trials were called for. Funding and conflicts: Funding not stated in the abstract. Read: abstract |
| Serban 2016 Effects of Quercetin on Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Am Heart Assoc · PMID 27405810 · DOI |
Systematic review meta analysis |
587 7 placebo-controlled trials (9 treatment arms), 587 people; searched to January 2015 |
Quercetin supplements (isolated quercetin) Capsule or tablet Trial amounts varied; the review split trials at 500 mg a day (studied in trials) Varied by trial · vs Placebo |
Quercetin lowered systolic and diastolic blood pressure on average. Trials using 500 mg a day or more showed a drop; trials using less did not show a clear drop, but a direct test found no significant difference between the two groups. Systolic WMD -3.04 mm Hg; diastolic WMD -2.63 mm Hg (Systolic -5.75 to -0.33; diastolic -3.26 to -2.01) Methods, limits and fundingOutcomes: Systolic and diastolic blood pressure Limitations: Small number of trials; the authors say the clinical meaning is unknown and more studies are needed. Blood pressure is a marker, not heart attacks or strokes. Funding and conflicts: Funding not stated in the abstract. Read: abstract |
| Turner 2015 A randomized, double-blind, placebo-controlled trial of resveratrol for Alzheimer disease. Neurology · PMID 26362286 · DOI |
Randomised controlled trial |
119 119 people with mild to moderate Alzheimer's disease, 52 weeks, multicentre phase II |
Resveratrol (oral) Oral supplement Started at 500 mg once a day and stepped up to 1,000 mg twice a day (studied in the trial) 52 weeks · vs Placebo |
Resveratrol and its main breakdown products were found in blood and spinal fluid. The most common side effects were nausea, diarrhoea and weight loss. Spinal fluid and blood amyloid beta 40 fell less with resveratrol than with placebo. Brain volume loss was greater with resveratrol than with placebo. The authors say the biomarker changes need further study to interpret; the abstract reports no clinical benefit. Directions only; numbers are not in the abstract (Not given in the abstract) Methods, limits and fundingOutcomes: Safety, Alzheimer's biomarkers in blood and spinal fluid, brain MRI volume; clinical outcomes were secondary Limitations: Biomarker changes are hard to interpret; greater brain volume loss with resveratrol was unexplained. Funding and conflicts: PubMed lists US NIH research support. Read: abstract |
| Walle 2004 High absorption but very low bioavailability of oral resveratrol in humans. Drug Metab Dispos · PMID 15333514 · DOI |
Pharmacokinetic study |
6 Six human volunteers given radio-labelled resveratrol by mouth and by vein |
14C-resveratrol Single oral dose 25 mg oral dose (studied in the trial) Single dose · vs Intravenous dose in the same people |
At least 70 percent of the oral dose was absorbed, but only trace amounts of unchanged resveratrol (under 5 ng/ml) appeared in blood, because the gut and liver quickly attach sulfate and glucuronic acid groups. Total resveratrol and its metabolites peaked at about 2 micromolar with a half-life of about 9 hours. Peak resveratrol plus metabolites 491 ng/ml; unchanged resveratrol under 5 ng/ml (Not applicable) Methods, limits and fundingOutcomes: Absorption, blood levels, metabolism Limitations: Six people, one dose; shows how the body handles resveratrol, not whether it helps health. Funding and conflicts: PubMed lists US government (PHS) research support. Read: abstract |
| Yadegar 2024 Effects and safety of resveratrol supplementation in older adults: A comprehensive systematic review. Phytother Res · PMID 38433010 · DOI |
Systematic review meta analysis |
10 randomised trials in older adults | Resveratrol supplements (some with exercise) Capsule or tablet Varied by trial; the authors say the best amount is not known Varied by trial · vs Placebo or control |
Results were mixed. Resveratrol plus exercise improved exercise adaptation and muscle function in healthy older adults and mobility in people with functional limits. It showed possible brain-protective effects in Alzheimer's disease and helped thinking in overweight people, but at high doses it raised some heart-disease risk markers. In older adults with diabetes or peripheral artery disease it was no better than placebo. No study reported significant adverse events. Not a pooled number (Not applicable) Methods, limits and fundingOutcomes: Exercise adaptation, muscle function, mobility, thinking, Alzheimer's biomarkers, heart-risk biomarkers, safety Limitations: Few, varied trials; the authors say the best amount, long-term effects and drug interactions are still unknown. Funding and conflicts: Funding not stated in the abstract. Read: abstract |
| s-lpi-flavonoids Linus Pauling Institute, Oregon State University: Flavonoids (reviewed February 2016) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-msk-quercetin Memorial Sloan Kettering Cancer Center: Quercetin, About Herbs (last updated 2023-10-10) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-msk-resveratrol Memorial Sloan Kettering Cancer Center: Resveratrol, About Herbs (last updated 2023-02-17) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-nccih-antioxidants NCCIH: Antioxidant Supplements, What You Need To Know (last updated July 2023) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text |
What we do not know yet
- No trial read showed that these supplements prevent heart attacks, strokes or diabetes.
- No safety information for pregnancy, breastfeeding or children was read.
- Liver safety (LiverTox) and the NIH, FDA and EFSA pages were not read.
- Quercetin absorption and special absorption-aid products were not compared.
- Resveratrol amounts per food portion were not read.
- No source on contamination or label accuracy of these supplements was read.
How new research is added
New studies are found by a saved PubMed search and placed in a review queue before the page changes.
Lab markers
What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".
Other 8
Systolic blood pressure
Lower (small) in trials
The top number in a blood-pressure reading; the pressure while the heart beats.
Low certaintyResults and what it means
Why it was measured
To see whether quercetin supplements lower blood pressure.
Statistical vs. clinical meaning
A small average drop with large differences between trials.
Safety implication
Blood-pressure medicine users should talk to a doctor before adding supplements.
| Study | Result | People | Product |
|---|---|---|---|
| 13 | WMD -3.04 mm Hg (95% CI -5.75 to -0.33) | 7 trials, 587 people | Quercetin supplements |
| 4 | WMD -3.09 mm Hg (95% CI -4.59 to -1.59) | 17 trials, 896 people | Quercetin or quercetin-enriched extract |
| 3 | WMD -1.9 mm Hg (95% CI -3.2 to -0.6), I2 88.3% | Umbrella review of 5 meta-analyses and 18 trials plus 5 newer trials | Quercetin supplements |
Flow-mediated dilation (FMD)
Higher in trials
An ultrasound test of how much an artery widens after a short blockage; it reflects how well the artery lining works.
Low certaintyResults and what it means
Why it was measured
To see whether resveratrol improves artery function.
Statistical vs. clinical meaning
A better test result, but not shown to mean fewer heart attacks or strokes.
Safety implication
None specific.
C-reactive protein and cholesterol
No change (HDL slightly lower) in trials
C-reactive protein is a blood marker of inflammation. Cholesterol and triglycerides are blood fats.
Evidence againstResults and what it means
Why it was measured
To see whether resveratrol changes heart-risk markers.
Statistical vs. clinical meaning
No benefit on inflammation or cholesterol; HDL was slightly lower.
Safety implication
The slight HDL fall is not the wanted direction.
| Study | Result | People | Product |
|---|---|---|---|
| 12 | CRP WMD -0.144 mg/L (-0.968 to 0.680); LDL -0.31 mg/dL; HDL -4.18 mg/dL (-6.54 to -1.82) | 10 trials (11 arms) | Resveratrol supplements |
Fasting glucose and HbA1c
Lower in one meta-analysis; neutral in the Cochrane review in trials
Fasting glucose is blood sugar after not eating. HbA1c reflects average blood sugar over about three months.
Mixed findingsResults and what it means
Why it was measured
To see whether resveratrol changes blood-sugar control.
Statistical vs. clinical meaning
Mixed results in small, short trials.
Safety implication
People on diabetes medicines should ask a doctor first.
| Study | Result | People | Product |
|---|---|---|---|
| 8 | Lower fasting glucose, insulin, HbA1c and HOMA-IR in people with diabetes; no change without diabetes (numbers not in the abstract) | 11 trials, 388 people | Resveratrol supplements |
| 5 | HbA1c MD 0.1 percent (-0.02 to 0.2); fasting glucose MD 2 mg/dL (-2 to 7) | 3 trials, 50 adults with type 2 diabetes | Oral resveratrol 10 mg, 150 mg or 1,000 mg a day |
Muscle soreness and creatine kinase
Lower in trials
Creatine kinase is an enzyme that leaks into the blood from damaged muscle.
Low certaintyResults and what it means
Why it was measured
To see whether quercetin speeds recovery after hard exercise.
Statistical vs. clinical meaning
Lower soreness and muscle-damage marker in small, short studies.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 11 | Soreness SMD -1.33; creatine kinase SMD -1.15 | 13 studies, 249 people | Quercetin about 1,000 mg a day, up to 12 weeks |
VO2max and endurance performance
Slightly higher in trials
VO2max is the most oxygen the body can use during hard exercise.
Low certaintyResults and what it means
Why it was measured
To see whether quercetin improves endurance.
Statistical vs. clinical meaning
A trivial gain; the authors of one review judge it unlikely to matter.
Safety implication
None specific.
Total nasal symptom score
Lower in trials
A score of sneezing, itching, runny and blocked nose in allergic rhinitis.
Low certaintyResults and what it means
Why it was measured
To see whether polyphenol products ease hay fever.
Statistical vs. clinical meaning
Lower symptom scores, but products differ and certainty is low to very low.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 7 | SMD 0.73 in combined analysis; low to very low certainty | 13 trials, 823 people | Mixed polyphenol products (catechins, quercetin and others) |
Amyloid beta 40 and brain volume
Amyloid beta 40 fell less; brain volume loss greater in trials
Amyloid beta 40 is a protein measured in blood and spinal fluid in Alzheimer's research. Brain volume is measured on MRI.
Very low certaintyResults and what it means
Why it was measured
To see whether resveratrol changes Alzheimer's disease biomarkers.
Statistical vs. clinical meaning
The meaning of these biomarker changes is unclear.
Safety implication
Greater brain volume loss with resveratrol was not explained.
| Study | Result | People | Product |
|---|---|---|---|
| 14 | Amyloid beta 40 declined less with resveratrol than placebo; brain volume loss was greater with resveratrol (numbers not in the abstract) | 119 people with mild to moderate Alzheimer's, 52 weeks | Resveratrol up to 1,000 mg twice a day |
Safety
What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.
Main points to know 4
- Not enough long-term safety data for high amounts of quercetin. A 2018 review says side effects of quercetin supplements were rarely reported and were mild, but there are no adequate data on long-term use (over 12 weeks) of 1,000 mg a day or more. Animal studies raised two possible concerns: worse kidney damage in kidneys that are already damaged, and promotion of tumours that depend on oestrogen. These are animal findings and may not apply to people. Narrative review and animal studies 2 17
- Medicine interactions (both compounds). Both compounds may change how the body handles some medicines. For quercetin, MSK reports lab findings on liver enzymes CYP3A4 and CYP2C19, animal findings for losartan and tamoxifen, and one case report of a raised INR in a man on warfarin. For resveratrol, MSK reports that 1 gram a day for 4 weeks inhibited CYP3A4, CYP2D6 and CYP2C9 and induced CYP1A2 in healthy volunteers, and that it may raise bleeding risk with blood thinners. Ask a pharmacist before combining either with prescription medicines. Lab, animal, small human and case report evidence 18 19 2
- Cancer treatment and hormone-sensitive cancers. NCCIH says antioxidant supplements might reduce the effectiveness of cancer treatments that work by creating reactive oxygen molecules, and advises checking with the cancer care team. MSK says quercetin may interfere with some chemotherapy drugs, and that resveratrol has oestrogen-like activity that in some experiments stimulated cancer cell growth. A high-dose micronized resveratrol study in multiple myeloma was stopped for serious events including kidney failure (as reported by MSK). Authoritative guidance, lab data and a stopped trial 20 18 19
- Resveratrol in Alzheimer's disease: greater brain volume loss. In a 52-week trial of 119 people with Alzheimer's disease, resveratrol (up to 1,000 mg twice a day) was linked to greater brain volume loss than placebo, plus nausea, diarrhoea and weight loss. The meaning of the brain volume finding is unclear. Randomised trial 14
Side effects 6
| Effect | How often | Severity and recovery | Evidence |
|---|---|---|---|
| Stomach upset and diarrhoea (resveratrol) The Cochrane review of 3 small diabetes trials found no reported adverse events but rates that evidence very low. | MSK lists mild to moderate stomach symptoms and diarrhoea at high daily amounts (2.5 g and 5 g). The Alzheimer's trial listed nausea and diarrhoea as most common; frequencies are not in the abstract. | Mild to moderate Not stated in the sources read. | Authoritative guidance and randomised trial 19 14 |
| Weight loss (resveratrol, high amounts) Only one trial; an older-adult review found no significant adverse events. | Listed among the most common adverse events in one Alzheimer's trial; frequency not in the abstract. | Not stated Not stated | Randomised trial 14 |
| Headache and tingling (quercetin, rare) The 2018 review says adverse effects in human studies were rare and mild. | In a 30-person prostatitis trial, one headache and one case of tingling in the limbs with quercetin 1,000 mg a day for a month; both stopped after the study (LPI). | Mild Resolved after the study ended. | Single trial summary 17 |
| Kidney toxicity (quercetin by vein, very high amounts) Oral supplement effects on kidneys are not established; animal data suggest caution if the kidneys are already damaged. | In a phase I cancer trial, quercetin given by vein at up to 51.3 mg/kg was linked to kidney toxicity; at 10.5 mg/kg and above it caused nausea, vomiting, flushing and breathlessness (LPI). This was an injection, not a capsule. | Serious at very high injected amounts Not stated | Phase I trial summary 17 2 |
| Contact dermatitis (resveratrol in a skin cream) A skin reaction to a cream, not to supplements. | One case report cited by MSK. | Not stated Not stated | Case report 19 |
| Slightly lower HDL cholesterol (resveratrol) Marker change; its health meaning is not shown. | HDL fell by about 4 mg/dL on average in a pooled analysis of 10 trials. | Small marker change Not stated | Meta-analysis 12 |
Liver
No liver injury case or LiverTox entry for quercetin or resveratrol was read. LiverTox could not be opened for this page, so liver safety is unknown here.
How often. No frequency was found.
Monitoring. No agency monitoring advice was found.
This is a safety connection. It is not evidence that Polyphenols: Quercetin and Resveratrol supports liver health.
Medicines and supplements 8
| With | Why it matters | Importance | Evidence | What to do |
|---|---|---|---|---|
| Warfarin and other blood thinners (quercetin) prescription | Not established. MSK reports one case. | A 79-year-old man on stable warfarin had a raised INR after starting quercetin; it returned to normal after he stopped. | Case report Very low certainty 18 | Tell your prescriber or pharmacist before adding quercetin to warfarin. |
| Blood thinners and antiplatelets (resveratrol) prescription | Resveratrol inhibits platelet clumping in lab experiments (MSK). | MSK says the clinical relevance is not yet determined, but use with antiplatelet drugs may raise bleeding risk. | Lab and authoritative guidance Very low certainty 19 | Ask a doctor or pharmacist before combining. |
| Drugs cleared by CYP3A4 and CYP2C19 enzymes (quercetin) prescription | Quercetin inhibited these liver enzymes in laboratory tests (MSK). | MSK says clinical relevance is not known. | Lab Very low certainty 18 | Ask a pharmacist. |
| Drugs cleared by CYP3A4, 2D6, 2C9 and 1A2 enzymes (resveratrol) prescription | In healthy volunteers taking 1 gram a day for 4 weeks, resveratrol inhibited CYP3A4, CYP2D6 and CYP2C9 and induced CYP1A2 (MSK). | It can change blood levels of drugs cleared by these enzymes. | Small human study Low certainty 19 | Ask a pharmacist about your medicines. |
| Losartan and tamoxifen (quercetin) prescription | In animal and preclinical studies quercetin raised exposure to losartan and tamoxifen (MSK). | MSK says clinical relevance has yet to be determined. | Animal and preclinical Very low certainty 18 | Ask a pharmacist. |
| Carbamazepine (resveratrol-rich Polygonum cuspidatum) prescription | In mice, a resveratrol-rich herbal supplement raised carbamazepine levels (MSK). | Clinical relevance has not been determined. | Animal research Very low certainty 19 | Ask a pharmacist. |
| Chemotherapy and radiotherapy prescription | Antioxidants may reduce the effect of treatments that work through reactive oxygen molecules (NCCIH). | NCCIH advises checking with the cancer care team before antioxidant supplements; MSK says quercetin may interfere with certain chemotherapy drugs. | Authoritative guidance Low certainty 20 18 | Check with the oncology team before any antioxidant supplement. |
| Diabetes medicines (resveratrol) prescription | Resveratrol may lower blood sugar in some pooled trials. | Whether this adds to diabetes medicines was not shown in the sources read. | Not established Very low certainty 8 5 | Ask a doctor before adding resveratrol to diabetes medicines. |
Who should check first 6
| Situation | Advice | Evidence |
|---|---|---|
| Pregnancy and breastfeeding | No source read gave safety information for quercetin or resveratrol supplements in pregnancy or breastfeeding. The LactMed page could not be opened. Ask a doctor or pharmacist before use. | Gap |
| Children | No source read covered quercetin or resveratrol supplements in children. Ask a doctor or pharmacist. | Gap |
| Kidney disease | Animal studies suggest quercetin could worsen kidney damage that is already present, and very high injected amounts caused kidney toxicity in a cancer trial. Ask a doctor before use if you have kidney disease. | Narrative review (animal studies) and phase I trial summary 2 17 |
| Hormone-sensitive cancers (breast, prostate, others) | Resveratrol has oestrogen-like activity and quercetin was linked to tumour promotion in oestrogen-dependent animal models. MSK says use should be discussed with the treating physician. | Lab and animal data and authoritative guidance 19 2 |
| Bleeding disorders or planned surgery | Resveratrol inhibits platelet clumping in lab studies and one case report links quercetin to a raised INR on warfarin. Tell your surgical team about any supplement. | Lab and case report 19 18 |
| Alzheimer's disease | One trial found greater brain volume loss with resveratrol. Do not use it for memory problems without medical advice. | Randomised trial 14 |
Overdose, product quality and regulators
Summary. Side effects in human studies of quercetin were rare and mild. Resveratrol caused stomach upset at high amounts. Very high injected quercetin harmed kidneys in cancer patients, and a high-dose resveratrol study in myeloma was stopped for serious events.
Animal. The 2018 review reports animal studies suggesting quercetin can enhance toxic effects in a damaged kidney and promote oestrogen-dependent tumours.
High dose or long term signals. No adequate data on use of 1,000 mg or more of quercetin beyond 12 weeks. For resveratrol, stomach symptoms at 2.5 g and 5 g a day (MSK).
Overdose response. Not described in the sources read. If someone takes a large amount and is unwell, call poison control or emergency services.
Genotoxicity. Not researched.
Contamination, label accuracy and product differences were not researched for this page.
Different forms. Quercetin supplements are mostly the free aglycone; rutin is a related sugar-bound form (LPI, review). Resveratrol supplements are commonly trans-resveratrol, and Japanese knotweed is a source (MSK). Special absorption-aid products exist, but no source read compared them. 2 17 19
| Body | Action | Date |
|---|---|---|
| Memorial Sloan Kettering Cancer Center (United States) | Quercetin: says it has not been shown to treat cancer or other diseases, that it may interfere with some chemotherapy, and lists lab or case-report drug interaction concerns (CYP3A4, CYP2C19, losartan, tamoxifen, warfarin). source | 2023-10-10 |
| Memorial Sloan Kettering Cancer Center (United States) | Resveratrol: says foods with resveratrol are generally safe to eat, high doses may cause stomach upset, it may raise bleeding risk with blood thinners, it inhibits several CYP enzymes, it has oestrogen-like activity, and lifespan extension is shown in yeast only. source | 2023-02-17 |
| National Center for Complementary and Integrative Health (NCCIH) (United States) | Says antioxidant supplements have not been shown to prevent cancer or heart disease, antioxidants may interfere with some cancer treatments, and people in treatment should check with their care team. source | 2023-07 |
| Linus Pauling Institute, Oregon State University (United States) | Says quercetin and its glycoside rutin are sold without prescription in the US, and that quercetin up to 1,000 mg a day for up to three months showed no significant adverse effects in studies it reviewed. This is a summary of studies, not advice to take quercetin. source | 2016-02 |
When to get medical help
- Black or bloody stools, nosebleeds that will not stop, easy bruising or blood in urine while taking a blood thinner and either supplement: seek medical help.
- Little or no urine, new swelling of the legs, or severe back pain after starting a supplement, especially with kidney disease: see a doctor urgently.
- Severe or lasting vomiting or diarrhoea, or signs of dehydration: seek medical care.
- Hives, swelling of the face or throat, or trouble breathing after a supplement: call emergency services.
- New confusion, fast memory decline or unexplained weight loss in someone with Alzheimer's disease taking resveratrol: contact their doctor.
Stop using the product and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.
General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.
Frequently asked questions
What are quercetin and resveratrol?
Do they work as antioxidants in the body?
Which foods have quercetin?
By the Linus Pauling Institute table, rocket, red onions, watercress and kale are the richest raw foods, with 22.6 to 66.2 mg per 100 g. Blueberries have 7.7 mg and brewed green tea 2.5 mg per 100 mL.
Which foods have resveratrol?
MSK lists grape skins and seeds, peanuts, pistachios, mulberries, blueberries and cranberries. Amounts per portion were not read.
Does quercetin lower blood pressure?
Does resveratrol protect the heart?
Does resveratrol help with diabetes?
Does quercetin help exercise or recovery?
Does quercetin help hay fever?
A 2025 review of polyphenol products, including quercetin, found lower nose symptom scores, but certainty was low to very low and it was not quercetin alone.
Does resveratrol slow ageing or help Alzheimer's?
Do they interact with medicines?
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Editorial transparency
- Written by
- AlternativeMed editorial team. Research compiled with AI assistance, then checked against the sources listed.
- Medical review
- None. This page has not been reviewed by a physician or pharmacist.
- First published
- 2026-10-26
- Last substantive update
- 2026-10-26
- How we research
- We started from our existing summary, read the MSK, NCCIH and Linus Pauling Institute pages in full, and re-read PubMed abstracts for 16 reviews and trials. Only abstracts were read for studies. Some pages (LactMed, LiverTox, NIH Office of Dietary Supplements) could not be opened and are marked unread.
- How we rate evidence
- See "How we rate evidence" in the Evidence tab.
- Independence
- No product is promoted on this page. No affiliate links are shown. Trials of supplements may have manufacturer links not stated in abstracts.
Sources 20
Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.
- Akbari M, Tamtaji OR, Lankarani KB, Tabrizi R, Dadgostar E, Kolahdooz F et al.. The Effects of Resveratrol Supplementation on Endothelial Function and Blood Pressures Among Patients with Metabolic Syndrome and Related Disorders: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.. High Blood Press Cardiovasc Prev. 2019. PMID 31264084. DOI 10.1007/s40292-019-00324-6. (abstract)
- Andres S, Pevny S, Ziegenhagen R, Bakhiya N, Schäfer B, Hirsch-Ernst KI, Lampen A. Safety Aspects of the Use of Quercetin as a Dietary Supplement.. Mol Nutr Food Res. 2018. PMID 29127724. DOI 10.1002/mnfr.201700447. (abstract)
- Arabi SM, Shahraki Jazinaki M, Chambari M, Bahrami LS, Maleki M, Sukhorukov VN et al.. The effects of Quercetin supplementation on cardiometabolic outcomes: An umbrella review of meta-analyses of randomized controlled trials.. Phytother Res. 2023. PMID 37654199. DOI 10.1002/ptr.7971. (abstract)
- Huang H, Liao D, Dong Y, Pu R. Effect of quercetin supplementation on plasma lipid profiles, blood pressure, and glucose levels: a systematic review and meta-analysis.. Nutr Rev. 2020. PMID 31940027. DOI 10.1093/nutrit/nuz071. (abstract)
- Jeyaraman MM, Al-Yousif NSH, Singh Mann A, Dolinsky VW, Rabbani R, Zarychanski R, Abou-Setta AM. Resveratrol for adults with type 2 diabetes mellitus.. Cochrane Database Syst Rev. 2020. PMID 31978258. DOI 10.1002/14651858.CD011919.pub2. (abstract)
- Kressler J, Millard-Stafford M, Warren GL. Quercetin and endurance exercise capacity: a systematic review and meta-analysis.. Med Sci Sports Exerc. 2011. PMID 21606866. DOI 10.1249/MSS.0b013e31822495a7. (abstract)
- Lai YR, Liao YH, Huang L, Phuong Linh HB, Utami FA, Del Giudice MM et al.. Clinical Effects of Polyphenolic Compounds on Allergic Rhinitis: A Systematic Review and Meta-Analysis.. J Allergy Clin Immunol Pract. 2025. PMID 40618891. DOI 10.1016/j.jaip.2025.06.032. (abstract)
- Liu K, Zhou R, Wang B, Mi MT. Effect of resveratrol on glucose control and insulin sensitivity: a meta-analysis of 11 randomized controlled trials.. Am J Clin Nutr. 2014. PMID 24695890. DOI 10.3945/ajcn.113.082024. (abstract)
- Mohammadipoor N, Shafiee F, Rostami A, Kahrizi MS, Soleimanpour H, Ghodsi M et al.. Resveratrol supplementation efficiently improves endothelial health: A systematic review and meta-analysis of randomized controlled trials.. Phytother Res. 2022. PMID 35833325. DOI 10.1002/ptr.7562. (abstract)
- Pelletier DM, Lacerte G, Goulet ED. Effects of quercetin supplementation on endurance performance and maximal oxygen consumption: a meta-analysis.. Int J Sport Nutr Exerc Metab. 2013. PMID 22805526. DOI 10.1123/ijsnem.23.1.73. (abstract)
- Rojano-Ortega D, Peña-Amaro J, Berral-Aguilar AJ, Berral-de la Rosa FJ. Quercetin supplementation promotes recovery after exercise-induced muscle damage: a systematic review and meta-analysis of randomized controlled trials.. Biol Sport. 2023. PMID 37398956. DOI 10.5114/biolsport.2023.121320. (abstract)
- Sahebkar A, Serban C, Ursoniu S, Wong ND, Muntner P, Graham IM et al.. Lack of efficacy of resveratrol on C-reactive protein and selected cardiovascular risk factors--Results from a systematic review and meta-analysis of randomized controlled trials.. Int J Cardiol. 2015. PMID 25885871. DOI 10.1016/j.ijcard.2015.04.008. (abstract)
- Serban MC, Sahebkar A, Zanchetti A, Mikhailidis DP, Howard G, Antal D et al.. Effects of Quercetin on Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.. J Am Heart Assoc. 2016. PMID 27405810. DOI 10.1161/JAHA.115.002713. (abstract)
- Turner RS, Thomas RG, Craft S, van Dyck CH, Mintzer J, Reynolds BA et al.. A randomized, double-blind, placebo-controlled trial of resveratrol for Alzheimer disease.. Neurology. 2015. PMID 26362286. DOI 10.1212/WNL.0000000000002035. (abstract)
- Walle T, Hsieh F, DeLegge MH, Oatis JE Jr, Walle UK. High absorption but very low bioavailability of oral resveratrol in humans.. Drug Metab Dispos. 2004. PMID 15333514. DOI 10.1124/dmd.104.000885. (abstract)
- Yadegar S, Mohammadi F, Yadegar A, Mohammadi Naeini A, Ayati A, Milan N et al.. Effects and safety of resveratrol supplementation in older adults: A comprehensive systematic review.. Phytother Res. 2024. PMID 38433010. DOI 10.1002/ptr.8171. (abstract)
- . Linus Pauling Institute, Oregon State University: Flavonoids (reviewed February 2016). . . (full-text)
- . Memorial Sloan Kettering Cancer Center: Quercetin, About Herbs (last updated 2023-10-10). . . (full-text)
- . Memorial Sloan Kettering Cancer Center: Resveratrol, About Herbs (last updated 2023-02-17). . . (full-text)
- . NCCIH: Antioxidant Supplements, What You Need To Know (last updated July 2023). . . (full-text)
Where to buy
Check the label first. Whatever you buy, look for these:
- The amount of the active ingredient per serving, not just the front-label claim
- A third-party testing mark (USP, NSF or ConsumerLab)
- Other ingredients and allergens
- Ask a pharmacist about interactions with your medicines
Talk to a pharmacist or doctor before you start any supplement, especially if you take medicines. See the Safety tab for interactions.
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