Quercetin information, FAQ and product listing page. This page contains information and frequently asked questions about quercetin as well as a complete list of products containing quercetin.

What is quercetin and what does it do?

Quercetin is part of a group of plant pigments known as flavonoids. Flavonoids are known as being responsible for the colors of many different fruits, flowers, and vegetables. Quercetin and other flavonoids for that matter are known to provide a variety of health-promoting benefits.

Quercetin acts as antihistamines, which are very useful in reducing allergy symptoms. They also help reduce inflammation that is associated with different forms of arthritis. Quercetin also has a role as an antioxidant that helps combat free radicals, scavenging damaging particles that roam our body and derive from cigarette smoke, pollution, and others. They also occur naturally In the body and have the ability to damage cell membranes and can even cause certain medical conditions like cancer and heart disease.

Quercetin and other antioxidants help neutralize these free radicals and may reduce or possibly even prevent the damage they can cause.

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What are the benefits of taking quercetin?

Quercetin gives us a plethora of possible therapeutic uses, particularly dealing with preventing and treating certain conditions. Quercetin also seems to work better when used with bromelain, a digestive enzyme that can be found in pineapples. This is especially true when trying to find allergies and inflammation – so remember that when next spring rolls around.

Allergies and Asthma

Quercetin slows down and can even prevent the production of histamine and other allergic and inflammatory related substances. You may have heard of antihistamines, which combat histamine – a substance that provides you with allergy symptoms like runny noses, hives, swelling, and watery eyes.

Heart Disease

Studies and research performed on animals have found that the flavonoids quercetin, catacehins, and resveratrol (all found in red wine) have the ability to help reduce the risk of plaque buildup on the articles. This can lead to a heart attack and stroke. These flavonids appear to help protect against the damage caused by LDL (the bad cholesterol), preventing death from heart disease. More human-studies are needed however to prove these findings in animals.

Arthritis

Tests performed on animals have also shown that quercetin prevents the type of inflammation that can possibly appear in the joints of those with arthritis. Those with rheumatoid arthritis have reported an improvement in symptoms when switching from a Western diet to a vegan one, which contained a lot of berries, fruits, nuts, vegetables, as well as antioxidants, like quercetin.

Prostate Health

Quercetin may help improve pain, as well other symptoms with men dealing with chronic prostatitis (inflaming of the prostate). Some studies have indicated that quercetin have the ability to prevent the growth of prostate cancer cells in tube tests. However, more studies are needed to show the benefits in men.

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Who can benefit from taking quercetin?

Because of the wide-reaching benefits of quercetin, everybody can benefit from quercetin. Men aging that are more susceptible to prostate cancer, as well as both men and women that are aging can benefit due to its positive effects in fighting arthritis.

And due to quercetin’s role in fighting cholesterol and heart disease, if you have had or are currently on a diet of fatty foods, you should especially consider supplementing.

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How much quercetin should I take?

As an allergy medication, the recommended adult dosage should be converted downward to account for the child’s weight. Typically, an adult dosage is calculated on the basis of 150 lbs. That means if a child weighs 50 lbs, the correct dose of quercetin for a child would be approximately 1/3 of the dosage the adult would take.

For adults, general supplementation can vary from 100 to 250 mg three times a day. Taken for allergy symptoms, 250 to 600 mg per day is the recommended dosage several times a day. If taken for chronic hives, quercetin should consist of 200 to 400 mg doses taken three times daily, approximately 20 minutes prior to each meal.

The amount of quercetin you take depends on the health condition being treated. Of course, you should always strictly follow the label directions of the supplement you are taking.

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Does quercetin have any side effects?

There have been no adverse side effects reported.

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References:

Sources used: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 Biomarkers Prevent . 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.