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Table of Contents > Supplements > Quercetin
Dietary Sources
Available Forms
How to Take It
Possible Interactions
Supporting Research


Quercetin belongs to a group of plant pigments called flavonoids that are largely responsible for the colors of many fruits, flowers, and vegetables. Flavonoids, such as quercetin, provide many health-promoting benefits. They act as antihistamines (which are useful in reducing allergy symptoms) and help reduce inflammation associated with various forms of arthritis. Quercetin also works as an antioxidant by scavenging damaging particles in the body known as free radicals. These particles occur naturally in the body but can damage cell membranes, interact with genetic material, and possibly contribute to the aging process as well as the development of a number of conditions including heart disease and cancer. Antioxidants such as quercetin can neutralize free radicals and may reduce or even help prevent some of the damage they cause.


Quercetin offers a variety of potential therapeutic uses, primarily in the prevention and treatment of the conditions listed below. Of note is that quercetin seems to work better when used in conjunction with bromelain, a digestive enzyme found in pineapples, particularly for allergies and inflammation.

Allergies, Asthma, Hayfever and Hives
Quercetin inhibits the production and release of histamine and other allergic/inflammatory substances. Histamine is a substance that contributes to allergy symptoms such as a runny nose, watery eyes, hives, and swelling of soft tissue including the face and lips.

Heart Disease
Test tube, animal, and some population-based studies suggest that the flavonoids quercetin, resveratrol, and catechins (all found in high concentration in red wine) may help reduce the risk of atherosclerosis (plaque build up in the arteries that can lead to heart attack or stroke). By acting as antioxidants, these nutrients appear to protect against the damage caused by LDL ("bad") cholesterol and may help prevent death from heart disease. Additional rigorous studies in people are needed to confirm these findings.

High Cholesterol
Flavonoids, like quercetin, from red wine or orange juice may help lower cholesterol levels.

Eye Disorders
Free radicals are thought to contribute to the development of certain eye disorders including cataracts and macular degeneration (a disorder that leads to lens damage and possibly blindness). Flavonoids, such as quercetin, neutralize free radicals and may play a role in the prevention and/or treatment of these eye conditions.

In a study of 3,072 adults with symptoms of macular degeneration, moderate red wine consumption (a source of quercetin) offered some protection against the development and progression of the disease. Dark berries, such as blueberries, blackberries, and dark cherries, are also high in flavonoids. Some suggest that eating these fruits regularly may also offer benefit for preventing macular degeneration.

Similarly, animal studies suggest that quercetin inhibits the activity of compounds that contribute to the development of cataracts.

According to laboratory and animal studies, quercetin has anti-inflammatory properties. In test tubes, for example, quercetin inhibits the type of inflammation that can occur in the joints of those with arthritis. In addition, there are reports of people with rheumatoid arthritis who experienced an improvement in their symptoms when they switched from a typical Western diet to a vegan diet with lots of uncooked berries, fruits, vegetables, nuts, roots, seeds, and sprouts containing, amongst other antioxidants, quercetin.

Similar to the case reports for arthritis, people with fibromyalgia who switched from a typical Western diet to a vegan diet high in flavonoids such as quercetin experienced improvement in their symptoms.

Prostate Health
Some studies suggest that quercetin improves pain and other symptoms in men with chronic prostatitis (inflammation of the prostate). In addition, preliminary laboratory studies indicate that quercetin may inhibit the growth of prostate cancer cells in test tubes. How this will ultimately translate to prevention or treatment of prostate cancer in men is unknown at this time.

Quercetin and other flavonoids from fruits and vegetables have long been considered important substances to possibly help prevent cancer. New laboratory studies are suggesting that this belief may be accurate. Quercetin and other flavonoids have been shown in animal and test tube studies to inhibit the growth of cancer cells, including those from breast, colon, prostate, and lung tumors.

One study evaluating quercetin in humans included 11 people with various forms of cancer. This study found that quercetin reduced the actual tumor size in two people and inhibited the activity of a protein that plays a role in tumor growth in nine of the 11 people. More studies are needed to further explore the possible beneficial effects of quercetin in people.

Researchers are also hopeful that quercetin and other flavonoids may prove to enhance the action of anti-cancer drugs. This issue, however, of using anti-oxidants at the same time as chemotherapy or radiation to treat cancer is controversial. Until more is know, it should likely be avoided.

Canker Sores
Quercetin may reduce the frequency of mouth sores and produce mild symptomatic relief.

Researchers have been evaluating medicinal plants in the Democratic Republic of Congo that have been used traditionally to treat diarrhea and dysentery. What they have found is that flavonoids, such as quercetin, are among the active ingredients in these plants. Studies in Russia regarding the use of quercetin, along with other supplements and/or conventional medications, to treat dysentery caused by infections such as Shigella have shown some promise.

Dietary Sources

Fruits and vegetables -- particularly citrus fruits, apples, onions, parsley, tea, and red wine -- are the primary dietary sources of quercetin. Olive oil, grapes, dark cherries, and dark berries, such as blueberries, blackberries, and bilberries are also high in flavonoids including quercetin.

Available Forms

Quercetin supplements are available in several strengths in powder or capsule form. They are often packaged with bromelain (an enzyme found in pineapple) as an anti-inflammatory agent. Bromelain exerts anti-inflammatory and anti-allergy activity of its own and also increases the absorption of quercetin. Other flavonoid-rich extracts include those from grape seed, bilberry, Ginkgo biloba, and green tea.

How to Take It


  • Allergies: The recommended adult dose should be adjusted to account for the child's weight. Most adult dosages are calculated on the basis of a 150 lb (70 kg) adult. Therefore, if the child weighs 50 lb (20 to 25 kg), the appropriate dose of quercetin for this child would be 1/3 of the adult dosage.


Recommended adult dosages of quercetin vary depending on the health condition being treated. The following are guidelines for some of its common uses:

  • General supplementation: 100 to 250 mg three times per day.
  • Allergy symptoms: 250 to 600 mg per day divided in several doses
  • Chronic hives: 200 to 400 mg of quercetin three times daily, taken approximately 20 minutes before each meal

If used with bromelain, the amount of bromelain should be equal to the amount of quercetin.


No adverse effects from the use of quercetin have been reported. However, because supplements may have side effects or interact with medications, they should be taken only under the supervision of a knowledgeable healthcare provider.

Possible Interactions

If you are currently being treated with any of the following medications, you should not use quercetin supplements without first talking to your healthcare provider.

Test tube and animal studies suggest that quercetin may enhance the effects of doxorubicin and cisplatin, two chemotherapy medications used to treat cancer. More research is needed to determine if quercetin has any application to people being treated with either of these agents. In addition, use of antioxidants at the same time as chemotherapy is somewhat controversial. Therefore, more research is needed before conclusions about safety and effectiveness can be drawn.

Supporting Research

Cai J, Nelson KC, Wu M, Sternberg P Jr, Jones DP. Oxidative damage and protection of the RPE. Prog Retin Eye Res. 2000;19(2):205-221.

Chan MM, Mattiacci JA, Hwang HS, Shah A, Fong D. Synergy between ethanol and grape polyphenols, quercetin, and resveratrol, in the inhibition of the inducible nitric oxide synthase pathway. Bio Pharm. 2000;60(10):1539-1548.

Constant J. Alcohol, ischemic heart disease, and the French paradox. Clin Card. 1997;20(5):420-424.

Duthie SJ, Collins AR, Duthie GG, Dobson VL. Quercetin and myricetin protect against hydrogen peroxide-induced DNA damage (strand breaks and oxidised pyrimidines) in human lymphocytes. Mutat Res. 1997;393(3):223-231.

Ferry DR, Smith A, Malkhandi J, et al. Phase I clinical trial of the flavonoid quercetin pharmacokinetics and evidence for in vivo tyrosine kinase inhibition. Clin Cancer Res. 1996;2(4):659-668.

Gross M, Pfeiffer M, Martini M, Campbell D, Slavin J, Potter J. The quantitation of metabolites of quercetin flavonols in human urine. Cancer Epidemiol BiomarkersPrevent. 1996;5(9):711-720.

Guardia T, Rotelli AE, Juarez AO, Pelzer LE. Anti-inflammatory properties of plant flavonoids. Effects of rutin, quercetin, and hesperidin on adjuvant arthritis in rat. Farmaco. 2001;56(9):683-687.

Hanninen, Kaartinen K, Rauma AL, Nenonen M, Torronen R, Hakkinen AS, Adlercreutz H, Laakso J. Antioxidants in vegan diet and rheumatic disorders. Toxicology. 2000;155(1-3):45-53.

Hayek T, Fuhrman B, Vaya J, Rosenblat M, Belinky P, Coleman R et al. Reduced progression of atherosclerosis in apolipoprotein E-deficient mice following consumption of red wine, or its polyphenols quercetin or catechin, is associated with reduced susceptibility of LDL to oxidation and aggregation. Arterioscler Thromb Vasc Biol. 1997;17(11):2744-2752.

Head KA. Natural therapies for ocular disorders. Part 1: diseases of the retina. Alt Med Rev. Oct. 1999;(4):5:342-359.

Hofmann J, Fiebig HH, Winterhalter BR, Berger DP, Grunicke H. Enhancement of the antiproliferative activity of cis-diamminedichloroplatinum (II) by quercetin. Int J Cancer. 1990;45(3):536-539.

Hollman PC, Van Trijp JM, Mengelers MJ, De Vries JH, Katan, MB. Bioavailability of the dietary antioxidant flavonol quercetin in man. Cancer Lett. 1997;114(1-2):139-140.

Knekt P, Isotupa S, Rissanen H, Heliovaara M, Jarvinen R, Hakkinen S et al. Quercetin intake and the incidence of cerebrovascular disease. Eur J Clin Nut. 2000;54(5):415-417.

Knekt P, Jarvinen R, Reunanen A, Maatela J. Flavonoid intake and coronary mortality in Finland: a cohort study. BMJ (Clinical Research Ed.). 1996;312(7029):478-481.

Kurowska EM, Spence JD, Jordan J, Wetmore S, Freeman DJ, Piche LA, Serratore P. HDL-cholesterol-raising effect of orange juice in subjects with hypercholesterolemia. Am J Clin Nutr. 2000;72(5):1095-1100.

Lamson DW, Brignall MS. Antioxidants and cancer III: quercetin. Alt Med Rev. 2000;5(3):196-208.

Lee E, Choi EJ, Cheong H, Kim YR, Ryu SY, Kim KM. Anti-allergic actions of the leaves of Castanea crenata and isolation of an active component responsible for the inhibition of mas cell degranulation. Arch Pharm Res. 1999;22(3):320-323.

Longanga OA, Vercruysse A, Foriers A. Contribution to the ethnobotanical, phytochemical and pharmacological studies of traditionally used medicinal plants in the treatment of dysentery and diarrhoea in Lomela area, Democratic Republic of Congo (DRC). J Ethnopharmacol. 2000;71(3):411-423.

Otshudi AL, Foriers A, Vercruysse A, Van Zeebroeck A, Lauwers S. In vitro antimicorbial activity of six medicinal plants traditionally used for the treatment of dysentery and diarrhoea in Democratic Republic of Congo (DRC). Phytomedicine. 2000;7(2):167-172.

Otsuka H, Inaba M, Fuikikura T, Kunitomo M. Histochemical and functional characteristics of metachromatic cells in the nasal epithelium in allergic rhinitis: studies of nasal scrapings and their dispersed cells. J Allergy Clin Immunol. 1995;96(4):528-536.

Owen RW, Giacosa A, Hull WE, Haubner R, Spiegelhalder B, Bartsch H. The antioxidant/anticancer potential of phenolic compounds isolated from olive oil. Eur J Cancer. 2000a;36(10):1235-1247.

Owen RW, Mier W, Giacosa A, Hull WE, Spiegelhalder B, Bartsch H. Identification of lignans as major components in the phenolic fraction of olive oil. Clin Chem. 2000b;46(7):976-988.

Piantelli M, Maggiano N, Ricci R, et al. Tamoxifen and quercetin interact with type II estrogen binding sites and inhibit the growth of human melanoma cells. J Invest Dermatol. 1995;105(2):248-53.

Rodgers EH, Grant MH. The effect of the flavonoids, quercetin, myricetin, and epicatechin on the growth and enzyme activities of MCF7 human breast cancer cells. Chem Bio Interactions. 1998;116(3):213-228.

Sanderson J, McLauchlan WR, Williamson G. Querctein inhibits hydrogen peroxide-induced oxidation of the rat lens. Free Radic Biol Med. 1999;26(5-6):639-645.

Scambia G, Ranelletti FO, Benedetti Panici P, et al. Quercetin potentiates the effect of adriamycin in a multi-drug-resistant MCF-7 human breast-cancer cell line: P-glycoprotein as a possible target. Cancer Chemother Pharmacol. 1994;34:459-464.

Shils ME, Olson JA, Shike M, Ross AC. Modern Nutrition in Health and Disease. 9th ed. Baltimore, Md: Williams & Wilkins; 1999:1274-1277.

Shoskes DA, Zeitlin SI, Shahed A, Rajfer J. Quercetin in men with category III chronic prostatitis: a preliminary prospective, double-blind, placebo-controlled trial. Urology. 1999;54(6):960-963.

Thornhill SM, Kelly AM. Natural treatment of perennial allergic rhinitis. Alt Med Rev. 2000;5(5):448-454.

Trcihopoulou A, Katsouyanni K, Stuver S, Tzala L, Cnardellis C, Rimm E, Trichopoulos D. Consumption of olive oil and specific food groups in relation to breast cancer risk in Greece. J National Cancer Inst. 1995;87(2):110-116.

Van Golde PH, Sloots LM, Vermeulen WP, et al. The role of alcohol in the anti low density lipoprotein oxidation activity of red wine. Atherosclerosis. 1999;147(2):365-370.

Werbach MR. Nutritional Influences on Illness. 2nd ed. Tarzana, Calif: Third Line Press; 1993:179, 259, 267, 389.

White L, Mavor S. Kids, Herbs, Health. Loveland, Colo: Interweave Press; 1998:22, 84.

Xing N, Chen Y, Mitchell SH, Young CY. Quercetin inhibits the expression and function of the androgen receptor in LNCaP prostate cancer cells. Carcinogenesis. 2001;22(3):409-414.

Young JF, Nielsen SE, Haraldsdottir J, et al. Effect of fruit juice intake on urinary quercetin excretion and biomarkers of antioxidative status. Am J Clin Nutr. 1999; 69(1):87-94.

Review Date: April 2002
Reviewed By: Participants in the review process include: Jacqueline A. Hart, MD, Department of Internal Medicine, Newton-Wellesley Hospital, Harvard University and Senior Medical Editor Integrative Medicine, Boston, MA; Gary Kracoff, RPh (Pediatric Dosing section February 2001), Johnson Drugs, Natick, Ma; Steven Ottariono, RPh (Pediatric Dosing section February 2001), Veteran's Administrative Hospital, Londonderry, NH; Margie Ullmann-Weil, MS, RD, specializing in combination of complementary and traditional nutritional therapy, Boston, MA. All interaction sections have also been reviewed by a team of experts including Joseph Lamb, MD (July 2000), The Integrative Medicine Works, Alexandria, VA;Enrico Liva, ND, RPh (August 2000), Vital Nutrients, Middletown, CT; Brian T Sanderoff, PD, BS in Pharmacy (March 2000), Clinical Assistant Professor, University of Maryland School of Pharmacy; President, Your Prescription for Health, Owings Mills, MD; Ira Zunin, MD, MPH, MBA (July 2000), President and Chairman, Hawaii State Consortium for Integrative Medicine, Honolulu, HI.

Copyright © 2004 A.D.A.M., Inc

The publisher does not accept any responsibility for the accuracy of the information or the consequences arising from the application, use, or misuse of any of the information contained herein, including any injury and/or damage to any person or property as a matter of product liability, negligence, or otherwise. No warranty, expressed or implied, is made in regard to the contents of this material. No claims or endorsements are made for any drugs or compounds currently marketed or in investigative use. This material is not intended as a guide to self-medication. The reader is advised to discuss the information provided here with a doctor, pharmacist, nurse, or other authorized healthcare practitioner and to check product information (including package inserts) regarding dosage, precautions, warnings, interactions, and contraindications before administering any drug, herb, or supplement discussed herein.

  Uses of this Supplement
Breast Cancer
Colorectal Cancer
Lung Cancer
Macular Degeneration
Prostate Cancer
Rheumatoid Arthritis
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