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Table of Contents > Articles > Is Quercetin a Supplement for You?
Is Quercetin a Supplement for You?

Quercetin is best known for its effectiveness in treating asthma and allergies as well as its ability to fight viruses and inflammation. While these uses are fairly well established, you may have heard that quercetin can do far more, such as prevent strokes or fight cancer. Outlined below is what the research has shown on quercetin and why it is an effective remedy, and how you can obtain it.

To date, studies on quercetin have been very positive, showing that high dietary intake of quercetin may lower your risk for stroke and cardiovascular disease. There is evidence that quercetin has bone-building effects, which may make it a useful therapy for countering osteoporosis. Quercetin also appears to fight ulcers—it has been shown to inhibit the growth of the bacteria responsible for most stomach and small intestine ulcers. Other research has shown quercetin to be a potential aid to HIV treatment, and yes, quercetin even shows promise as a cancer therapy: studies report quercetin appears to kill cancer cells in certain cancers, including squamous cell cancers, leukemia, and cancers of the breast, lungs, ovaries, and colon. Of course, all of these study results need to be confirmed by further studies and research.

Quercetin is one of the bioflavonoids, the antioxidants that give color to fruits, vegetables, and flowers. Bioflavonoids help to keep blood vessels strong and to repair cartilage, tendons, and ligaments. Quercetin has the greatest antioxidant effect of all of the flavonoids. When it comes to battling asthma, quercetin has healing properties that nonsteroidal anti-inflammatory drugs (NSAIDs) and antihistamines lack—by repairing tissues, fibers, and membranes, it strengthens the entire respiratory system. In addition to relieving symptoms, quercetin decreases allergies and respiratory symptoms over time by regenerating tissues.

Where can you find quercetin? Foods with the highest levels of quercetin include onions, apples, red wine, tea, green tea, spices, and to a lesser extent green leafy vegetables and beans. Most people consume about 25 to 50 mg of quercetin daily. Healthy people can safely increase their intake to 250 to 1,000 mg daily. For chronic allergy, pain, inflammation, asthma, or sinusitis, take 500 to 6,000 mg daily, divided into several doses. Keep in mind that quercetin supplements come in various forms, and some are more usable by the body than others. Quercetin dihydrate is the most easily used by the body, followed by quercetin chalcone. In contrast, other quercetins, such as hesperidin, rutin, and rosehip, are far less effective.

Be sure to talk with your physician or pharmacist to determine whether quercetin might be beneficial for you. Some supplements should not be taken if you have certain medical conditions or are taking particular prescription medications.


Glossary

Nonsteroidal anti-inflammatory drugs (NSAIDs): A large class of drugs commonly used to relieve pain, reduce inflammation, and lower fevers. Side effects may include stomach upset and intestinal bleeding. Ibuprofen is a common NSAID.

Squamous cell cancer: Cancer in the form of a slow-growing tumor that is often found on the skin and has been caused by overexposure to the sun. Squamous cell cancer may also occur in the lungs, larynx, nose, bladder, anus, and cervix.


References

Catapano A. Antioxidant effect of flavonoids. Angiology. 1997;48(1):39-44.

Cross HJ, Tilby M, Chipman JK, Ferry DR, Gescher A. Effect of quercetin on the genotoxic potential of cisplatin. Int J Cancer. 1996;66:404-408.

de Vries JH, Janssen PL, Mollman PC, van Staveren WA, Katan MB. Consumption of quercetin and kaempferol in free-living subjects eating a variety of diets. Cancer Lett. 1997; 114:141-144.

Kandaswami C, Perkins E, Drzewiecki G, Soloniuk DS, Middleton E Jr. Differential inhibition of proliferation of human squamous cell carcinoma, gliosarcoma and embryonic fibroblast-lung cells in culture by plant flavonoids. Anticancer Drugs. 1992;3(5):525-530.

Kandaswami C, Perkins E, Soloniuk DS, Drzewiecki G, Middleton E Jr. Ascorbic acid enhanced antiproliferative effect of flavonoids on squamous cell carcinoma in vitro. Anticancer Drugs. 1993;4(1):92-96.

Keli SO, Hertog MG, Feskens EJ, Kromhout D. Dietary flavonoids, antioxidant vitamins, and incidence of stroke: the Zutphen study. Arch Intern Med. 1996;157:637-642.

Le Marchand L, Murphy SP, Hankin JH, Wilkens LR, Kolonel LN. Intake of flavonoids and lung cancer. J Natl Cancer Inst. 2000;92(2):154-160.

Pizzorno J, Murray M. Textbook of Natural Medicine. 2nd ed. Edinburgh: Churchill Livingstone; 1999:745-750.

Ranelletti FO, Maggiano N, Serra FG, et al. Quercetin inhibits p21-RAS expression in human colon cancer cell lines and in primary colorectal tumors. Int J Cancer. 2000;85(3):438-445.

Rice-Evans CA, et al. Antioxidant properties of phenolic compounds. Trends in Plant Science. April 1997;2(4):152-159.

Sziklai I, Ribari O. Flavonoids alter bone-remodeling in auditory ossicle organ cultures. Acta Otolaryngol Stockh. 1995:114-296-299.


Review Date: September 2000
Reviewed By: Integrative Medicine editorial

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.

 
RELATED INFORMATION
  Conditions
Asthma
Breast Cancer
Colorectal Cancer
HIV and AIDS
Leukemia
Lung Cancer
Osteoporosis
Sinusitis
Stroke
  Supplements
Quercetin
 

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