Quercetin — Benefits Deep Dive

Deep-Dive Articles

Back to Table of Contents

Table of Contents

1. Deep-Dive Articles
2. Four Lines of Quercetin Research
3. Research Papers: Allergy & Histamine
4. Research Papers: Cardiovascular Health
5. Research Papers: Senolytic Activity
6. Research Papers: Zinc Ionophore & Antiviral
7. Research Papers: Pharmacology, Bioavailability, Safety
8. External Authoritative Resources
9. Connections
10. Featured Videos

Four Lines of Quercetin Research

Quercetin's structure is a flavone ring system carrying five hydroxyl groups (2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one), and in laboratory studies it acts on several kinds of target. The research falls into the four areas covered by the deep-dive pages. Most of the mechanisms below come from cell and animal studies: for blood pressure, Larson and colleagues (2012) note that most proposed mechanisms were identified in animal models and relatively few have been corroborated in human studies.

1. Mast-cell inhibition — in cultured human mast cells, quercetin inhibited the rise in cytosolic calcium and the activation of NF-κB, and reduced the release of histamine, leukotrienes, prostaglandin D2 and the cytokines IL-6, IL-8 and TNF (Weng 2012). In the same study quercetin and cromolyn (both at 100 µM) were similarly effective against histamine and prostaglandin D2, quercetin was more effective against IL-8 and TNF release, and quercetin worked when added before the trigger, whereas cromolyn lost its effect unless added together with it. In rat intestinal mast cells, quercetin inhibited antigen-induced histamine release (Pearce 1984). None of these papers compares quercetin with cromolyn in people. The human allergy trials are small placebo-controlled studies in Japanese pollen allergy: 20 people taking enzymatically modified isoquercitrin had lower eye-symptom scores over the season (Kawai 2009), and 66 people taking 200 mg/day of a quercetin–lecithin phytosome formulation for 4 weeks reported improvement in several symptom scores (Yamada 2022). This research is covered on the Allergy & Histamine page.
2. Endothelial and blood-pressure effects — in 12 healthy men, a single 200 mg dose of quercetin raised plasma nitric-oxide products and lowered endothelin-1 (Loke 2008). In the Edwards 2007 crossover trial, 730 mg/day for 28 days lowered systolic and diastolic pressure by 7 and 5 mmHg in 22 people with stage 1 hypertension, did not change blood pressure in 19 people with prehypertension, and did not change markers of oxidative stress. Meta-analyses report average systolic reductions of 3.04 mmHg (7 trials, 587 patients; significant in trials using 500 mg/day or more, Serban 2016) and 3.09 mmHg (17 trials, 896 participants, Huang 2020); a 2023 umbrella review found a systolic reduction of 1.9 mmHg and no effect on diastolic pressure or lipids, with certainty of evidence ranging from very low to moderate (Arabi 2023). Quercetin prevents LDL oxidation in vitro (Hollman 1996), but 50–150 mg/day for two weeks did not change oxidized LDL in healthy volunteers (Egert 2008). In the Zutphen Elderly Study, higher flavonoid intake — mainly from tea, onions and apples — was associated with lower coronary mortality over five years in 805 men (Hertog 1993). This research is covered on the Cardiovascular Health page.
3. Senolytic activity, in combination with dasatinib — Zhu and colleagues (2015) found raised pro-survival networks in senescent cells; silencing nodes such as ephrins, PI3Kδ, p21, BCL-xL or plasminogen-activator inhibitor-2 killed senescent cells but not proliferating or quiescent cells. Of 46 agents tested, dasatinib and quercetin showed particular promise: dasatinib eliminated senescent human fat-cell progenitors, quercetin was more effective against senescent human endothelial cells and mouse bone-marrow stem cells, and the combination reduced senescent-cell burden in mice. Kirkland and Tchkonia (2020) list dasatinib, quercetin, fisetin and navitoclax as the first senolytic drugs. The human data are small pilots of the combination: an open-label study in 14 people with idiopathic pulmonary fibrosis (physical function improved, lung function unchanged; Justice 2019) and an open-label study in 9 people with diabetic kidney disease (fewer senescent cells in fat tissue and skin 11 days after a 3-day course; Hickson 2019). Kirkland and Tchkonia wrote that, until the clinical trials then under way are done, it is too early for senolytics to be used outside clinical trials. This research is covered on the Senolytic Activity page.
4. Zinc-ionophore and antiviral activity — Dabbagh-Bazarbachi and colleagues (2014) showed that quercetin and epigallocatechin gallate (EGCG), like the drug clioquinol, carried zinc into mouse liver-cancer (Hepa 1-6) cells and across the membrane of artificial liposomes. Separately, te Velthuis and colleagues (2010) found that zinc inhibits the RNA polymerase of SARS-coronavirus and equine arteritis virus in vitro, and that zinc combined with the ionophore pyrithione blocked their replication in cell culture; quercetin was not part of that study. In cell culture, quercetin reduced the infectivity and replication of herpes simplex virus type 1, poliovirus, parainfluenza virus type 3 and respiratory syncytial virus (Kaul 1985) and inhibited influenza A entry (Wu 2015). In people, a trial in 40 trained cyclists found fewer upper-respiratory infections in the two weeks after three days of intensive exercise with 1000 mg/day than with placebo (1 of 20 vs 9 of 20; Nieman 2007), while a 12-week trial in 1,002 community adults found no overall effect of 500 or 1000 mg/day on upper-respiratory infections (Heinz 2010). This research is covered on the Zinc Ionophore & Antiviral page.
5. Other laboratory findings — quercetin is studied for further anti-inflammatory and metabolic actions in cell and animal models, as are other dietary flavonols. Walle (2004) notes that whether flavonoids reach their intended sites of action in humans is largely unknown.

Absorption is the main practical complication. A 2019 pharmacokinetic paper describes quercetin's poor solubility and low oral absorption as its major drawbacks (Riva 2019). The form matters: in nine volunteers, absorption of quercetin from apples and from pure quercetin-3-rutinoside (the main quercetin glycoside in tea) was 30% of that from onions, whose quercetin is bound to glucose (Hollman 1997); in twelve volunteers, peak plasma levels after buckwheat tea or rutin were lower and later than after an onion supplement or quercetin-4′-O-glucoside (Graefe 2001). In that study only quercetin glucuronides, and no free quercetin, were detected in plasma; the main circulating compounds 1.5 hours after an onion meal were quercetin-3-glucuronide, 3′-methylquercetin-3-glucuronide and quercetin-3′-sulfate (Day 2001). Reported elimination half-lives differ between studies: 16.8 hours after fried onions in two subjects (Hollman 1996), 28 hours after onions and 23 hours after apples in nine subjects (Hollman 1997), and about 11 hours for all four preparations tested in twelve subjects (Graefe 2001); Hickson and colleagues (2019) describe dasatinib and quercetin as having elimination half-lives under 11 hours. In a 12-volunteer crossover study run by employees of the formulation's manufacturer, a quercetin–lecithin phytosome formulation produced plasma levels up to 20 times those usually obtained with unformulated quercetin (Riva 2019).

Laboratory and human concentrations differ. The cultured mast-cell experiments above used 100 µM quercetin (Weng 2012). In healthy volunteers taking 150 mg/day, the median peak plasma quercetin concentration was 431 nmol/L, with high variation between people (Egert 2008); after fried onions supplying 64 mg of quercetin, peak plasma levels were 196 ng/mL (Hollman 1996). In the Egert study, two weeks of 50–150 mg/day raised plasma quercetin but did not change antioxidant status, oxidized LDL, inflammation or metabolism.

Back to Table of Contents

Research Papers: Allergy & Histamine

1. Pearce FL, Befus AD, Bienenstock J (1984). Mucosal mast cells. III. Effect of quercetin and other flavonoids on antigen-induced histamine secretion from rat intestinal mast cells. Journal of Allergy and Clinical Immunology 73(6):819–823. — PubMed PMID: 6202731
2. Mlcek J, Jurikova T, Skrovankova S, Sochor J (2016). Quercetin and its anti-allergic immune response. Molecules 21(5):623. — PubMed PMID: 27187333
3. Jafarinia M, Sadat Hosseini M, Kasiri N, et al. (2020). Quercetin with the potential effect on allergic diseases. Allergy, Asthma & Clinical Immunology 16:36. — PubMed PMID: 32467711
4. Quercetin mast cell membrane stabilization mechanism — PubMed: Mast cell stabilization
5. Quercetin inhibition of FcepsilonRI signaling and tryptase release — PubMed: FcepsilonRI signaling
6. Mast cell activation syndrome (MCAS) and natural mast-cell stabilizers — PubMed: MCAS and natural stabilizers
7. Quercetin in allergic rhinitis randomized controlled trials — PubMed: Allergic rhinitis RCTs
8. Quercetin and chronic idiopathic urticaria — PubMed: Quercetin and urticaria
9. Quercetin asthma and airway hyperresponsiveness animal models — PubMed: Quercetin and asthma
10. Quercetin + bromelain co-administration absorption studies — PubMed: Quercetin + bromelain
11. Weng Z, Zhang B, Asadi S, et al. (2012). Quercetin is more effective than cromolyn in blocking human mast cell cytokine release and inhibits contact dermatitis and photosensitivity in humans. PLoS ONE 7(3):e33805. — PubMed PMID: 22470478
12. Kawai M, Hirano T, Arimitsu J, et al. (2009). Effect of enzymatically modified isoquercitrin, a flavonoid, on symptoms of Japanese cedar pollinosis: a randomized double-blind placebo-controlled trial. International Archives of Allergy and Immunology 149(4):359–368. — PubMed PMID: 19295240
13. Yamada S, Shirai M, Inaba Y, Takara T (2022). Effects of repeated oral intake of a quercetin-containing supplement on allergic reaction: a randomized, placebo-controlled, double-blind parallel-group study. European Review for Medical and Pharmacological Sciences 26(12):4331–4345. — PubMed PMID: 35776034

Back to Table of Contents

Research Papers: Cardiovascular Health

1. Edwards RL, Lyon T, Litwin SE, Rabovsky A, Symons JD, Jalili T (2007). Quercetin reduces blood pressure in hypertensive subjects. Journal of Nutrition 137(11):2405–2411. — PubMed PMID: 17951477
2. Serban MC, Sahebkar A, Zanchetti A, et al. (2016). Effects of quercetin on blood pressure: a systematic review and meta-analysis of randomized controlled trials. Journal of the American Heart Association 5(7):e002713. — PubMed PMID: 27405810
3. Sahebkar A (2017). Effects of quercetin supplementation on lipid profile: a systematic review and meta-analysis of randomized controlled trials. Critical Reviews in Food Science and Nutrition 57(4):666–676. — PubMed PMID: 25897620
4. Hertog MGL, Feskens EJM, Hollman PCH, Katan MB, Kromhout D (1993). Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study. The Lancet 342(8878):1007–1011. — PubMed PMID: 8105262
5. Loke WM, Hodgson JM, Proudfoot JM, et al. (2008). Pure dietary flavonoids quercetin and (-)-epicatechin augment nitric oxide products and reduce endothelin-1 acutely in healthy men. American Journal of Clinical Nutrition 88(4):1018–1025. — PubMed PMID: 18842789
6. Larson AJ, Symons JD, Jalili T (2012). Therapeutic potential of quercetin to decrease blood pressure: review of efficacy and mechanisms. Advances in Nutrition 3(1):39–46. — PubMed PMID: 22332099
7. Quercetin and endothelial nitric oxide synthase (eNOS) activation — PubMed: Quercetin and eNOS
8. Quercetin inhibition of LDL oxidation in vitro and in vivo — PubMed: Quercetin and LDL oxidation
9. Quercetin platelet aggregation inhibition mechanism — PubMed: Quercetin and platelets
10. Apple and onion flavonoid intake and cardiovascular outcomes cohort studies — PubMed: Apple/onion CV cohorts
11. Huang H, Liao D, Dong Y, Pu R (2020). Effect of quercetin supplementation on plasma lipid profiles, blood pressure, and glucose levels: a systematic review and meta-analysis. Nutrition Reviews 78(8):615–626. — PubMed PMID: 31940027
12. Arabi SM, Shahraki Jazinaki M, Chambari M, et al. (2023). The effects of quercetin supplementation on cardiometabolic outcomes: an umbrella review of meta-analyses of randomized controlled trials. Phytotherapy Research 37(11):5080–5091. — PubMed PMID: 37654199

Back to Table of Contents

Research Papers: Senolytic Activity

1. Zhu Y, Tchkonia T, Pirtskhalava T, et al. (2015). The Achilles' heel of senescent cells: from transcriptome to senolytic drugs. Aging Cell 14(4):644–658. — PubMed PMID: 25754370
2. Hickson LJ, Langhi Prata LGP, Bobart SA, et al. (2019). Senolytics decrease senescent cells in humans: preliminary report from a clinical trial of Dasatinib plus Quercetin in individuals with diabetic kidney disease. EBioMedicine 47:446–456. — PubMed PMID: 31542391 (corrigendum: PubMed PMID: 31982828)
3. Justice JN, Nambiar AM, Tchkonia T, et al. (2019). Senolytics in idiopathic pulmonary fibrosis: results from a first-in-human, open-label, pilot study. EBioMedicine 40:554–563. — PubMed PMID: 30616998
4. Kirkland JL, Tchkonia T (2020). Senolytic drugs: from discovery to translation. Journal of Internal Medicine 288(5):518–536. — PubMed PMID: 32686219
5. Yousefzadeh MJ, Zhu Y, McGowan SJ, et al. (2018). Fisetin is a senotherapeutic that extends health and lifespan. EBioMedicine 36:18–28. — PubMed PMID: 30279143
6. Xu M, Pirtskhalava T, Farr JN, et al. (2018). Senolytics improve physical function and increase lifespan in old age. Nature Medicine 24(8):1246–1256. — PubMed PMID: 29988130
7. Baker DJ, Wijshake T, Tchkonia T, et al. (2011). Clearance of p16Ink4a-positive senescent cells delays ageing-associated disorders. Nature 479(7372):232–236. — PubMed PMID: 22048312
8. Senescent-cell anti-apoptotic pathways (SCAPs) and BCL-2 family inhibition — PubMed: SCAPs and BCL-2 family
9. Senescence-associated secretory phenotype (SASP) and inflammaging — PubMed: SASP and inflammaging
10. Quercetin and PI3K / BCL-xL inhibition in senescent fibroblasts — PubMed: Quercetin and PI3K/BCL-xL

Back to Table of Contents

Research Papers: Zinc Ionophore & Antiviral

1. Dabbagh-Bazarbachi H, Clergeaud G, Quesada IM, et al. (2014). Zinc ionophore activity of quercetin and epigallocatechin-gallate: from Hepa 1-6 cells to a liposome model. Journal of Agricultural and Food Chemistry 62(32):8085–8093. — PubMed PMID: 25050823
2. Kaul TN, Middleton E Jr, Ogra PL (1985). Antiviral effect of flavonoids on human viruses. Journal of Medical Virology 15(1):71–79. — PubMed PMID: 2981979
3. te Velthuis AJ, van den Worm SH, Sims AC, et al. (2010). Zn2+ inhibits coronavirus and arterivirus RNA polymerase activity in vitro and zinc ionophores block the replication of these viruses in cell culture. PLoS Pathogens 6(11):e1001176. — PubMed PMID: 21079686
4. Wu W, Li R, Li X, et al. (2015). Quercetin as an antiviral agent inhibits influenza A virus (IAV) entry. Viruses 8(1):6. — PubMed PMID: 26712783
5. Lee M, Son M, Ryu E, et al. (2015). Quercetin-induced apoptosis prevents EBV infection. Oncotarget 6(14):12603–12624. — PubMed PMID: 26059439
6. Quercetin and rhinovirus replication inhibition — PubMed: Quercetin and rhinovirus
7. Quercetin and HSV-1 / HSV-2 herpes simplex inhibition — PubMed: Quercetin and HSV
8. Quercetin and hepatitis C virus replication — PubMed: Quercetin and HCV
9. Quercetin and dengue virus inhibition — PubMed: Quercetin and dengue
10. Quercetin and zinc combination upper respiratory infection trials — PubMed: Quercetin + zinc URI
11. Nieman DC, Henson DA, Gross SJ, et al. (2007). Quercetin reduces illness but not immune perturbations after intensive exercise. Medicine & Science in Sports & Exercise 39(9):1561–1569. — PubMed PMID: 17805089
12. Heinz SA, Henson DA, Austin MD, Jin F, Nieman DC (2010). Quercetin supplementation and upper respiratory tract infection: a randomized community clinical trial. Pharmacological Research 62(3):237–242. — PubMed PMID: 20478383

Back to Table of Contents

Research Papers: Pharmacology, Bioavailability, Safety

1. Hollman PCH, van Trijp JM, Buysman MN, et al. (1997). Relative bioavailability of the antioxidant flavonoid quercetin from various foods in man. FEBS Letters 418(1–2):152–156. — PubMed PMID: 9414116
2. Walle T (2004). Absorption and metabolism of flavonoids. Free Radical Biology & Medicine 36(7):829–837. — PubMed PMID: 15019968
3. Quercetin glucuronidation and sulfation phase-II metabolism — PubMed: Quercetin metabolism
4. Riva A, Ronchi M, Petrangolini G, Bosisio S, Allegrini P (2019). Improved oral absorption of quercetin from Quercetin Phytosome®, a new delivery system based on food grade lecithin. European Journal of Drug Metabolism and Pharmacokinetics 44(2):169–177. — PubMed PMID: 30328058 (the authors are employees of the formulation's manufacturer)
5. Egert S, Wolffram S, Bosy-Westphal A, et al. (2008). Daily quercetin supplementation dose-dependently increases plasma quercetin concentrations in healthy humans. Journal of Nutrition 138(9):1615–1621. — PubMed PMID: 18716159
6. Quercetin and vitamin C co-administration absorption studies — PubMed: Quercetin + vitamin C
7. Quercetin safety and toxicology in long-term human supplementation — PubMed: Quercetin safety
8. Quercetin and cyclosporine / cytochrome P450 drug interactions — PubMed: Quercetin drug interactions
9. Phenol-Explorer database quercetin content of common foods — PubMed: Phenol-Explorer quercetin
10. Andres S, Pevny S, Ziegenhagen R, et al. (2018). Safety aspects of the use of quercetin as a dietary supplement. Molecular Nutrition & Food Research 62(1). — PubMed PMID: 29127724
11. Hollman PC, vd Gaag M, Mengelers MJ, et al. (1996). Absorption and disposition kinetics of the dietary antioxidant quercetin in man. Free Radical Biology & Medicine 21(5):703–707. — PubMed PMID: 8891673
12. Graefe EU, Wittig J, Mueller S, et al. (2001). Pharmacokinetics and bioavailability of quercetin glycosides in humans. Journal of Clinical Pharmacology 41(5):492–499. — PubMed PMID: 11361045
13. Day AJ, Mellon F, Barron D, et al. (2001). Human metabolism of dietary flavonoids: identification of plasma metabolites of quercetin. Free Radical Research 35(6):941–952. — PubMed PMID: 11811545
14. Rusznyák S, Szent-Györgyi A (1936). Vitamin P: flavonols as vitamins. Nature 138:27. — doi:10.1038/138027a0

Back to Table of Contents

External Authoritative Resources

• Linus Pauling Institute — Flavonoids Micronutrient Information Center — comprehensive review of quercetin and other dietary flavonoids
• NIH Office of Dietary Supplements — Dietary Supplement Fact Sheets
• ClinicalTrials.gov — All active quercetin trials
• Phenol-Explorer — Database of polyphenol content in foods (quercetin food sources)
• PubMed — All research on quercetin (more than 35,000 records, October 2026)

Back to Table of Contents

Connections

• Quercetin (Main Page)
• Quercetin for Allergy & Histamine
• Quercetin for Cardiovascular Health
• Quercetin Senolytic Activity (D+Q)
• Quercetin Zinc Ionophore & Antiviral
• Fisetin (Sister Flavonol)
• Spermidine
• Zinc (Ionophore Partner)
• Vitamin C
• Immune Boosting
• Longevity Protocols
• Allergies
• Cardiovascular Disease
• Apples
• Onions
• History

Back to Table of Contents

Featured Videos