Quercetin: One Opinion

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http://blueprint.bluecrossmn.com/topic/topic100587860

 

Quercetin

 

Introduction

You may have heard of the " French paradox. " The French diet is very high in fat

and cholesterol (just think of pt de fois gras and croissants), yet France has

one of the world's lowest rates of heart disease. One theory for this

discrepancy is that another major player in the French diet -- red wine --

protects the arteries of the heart.

 

A natural antioxidant found in red wine, quercetin protects cells in the body

from damage by free radicals (naturally occurring but harmful substances). Heart

disease and high cholesterol are thought to be at least partly caused by free

radical damage to blood vessels, so it makes sense that quercetin might help

protect against heart attacks and strokes. Quercetin belongs to a class of

water-soluble plant coloring agents called bioflavonoids, a type of nutrient

that we're learning more about all the time. Although they don't seem to be

essential to life, it's likely that we need them for optimal health.

 

Another intriguing finding is that quercetin may help prevent immune cells from

releasing histamine, the chemical that initiates the itching, sneezing, and

swelling of an allergic reaction. Based on this very preliminary research,

quercetin is often recommended as a treatment for allergies and asthma.

Sources

Quercetin is not an essential nutrient. It is found in red wine, grapefruit,

onions, apples, black tea, and, in lesser amounts, in leafy green vegetables and

beans. However, to get a therapeutic dosage, you'll have to take a supplement.

 

Quercetin supplements are available in pill and tablet form.

Therapeutic Dosages

A typical dosage is 200 to 400 mg 3 times daily. Quercetin may be better

absorbed if taken on an empty stomach.

Therapeutic Uses

The most popular use of quercetin is as a treatment for allergic conditions such

as asthma, hay fever, eczema, and hives. This use is based on test-tube research

showing that quercetin prevents certain immune cells from releasing histamine,

the chemical that triggers an allergic reaction.1,2 It also may block other

substances involved with allergies.3 But we have no evidence as yet that taking

quercetin supplements will reduce your allergy symptoms.

 

Prostatitis is an inflammation or infection of the prostate gland. In some

cases, no cause can be discovered. The condition causes chronic pain and

difficulty with urination, and is sometimes called chronic pelvic pain syndrome.

Conventional treatment for this condition is often unsatisfactory. According to

a 1-month double-blind placebo-controlled trial of 30 men with chronic pelvic

pain, quercetin at a dose of 500 mg twice daily might be helpful.4

 

A small double-blind placebo-controlled trial found that a supplement containing

quercetin reduced symptoms of interstitial cystitis.5

 

Very preliminary evidence also suggests that quercetin might help prevent heart

disease and strokes.6-10

 

Test-tube and animal research also suggests that quercetin might have anticancer

properties.11-15

 

An animal study found that quercetin might protect rodents with diabetes from

forming cataracts.16 Another intriguing finding of test-tube research is that

quercetin seems to prevent a wide range of viruses from infecting cells and

reproducing once they are inside cells. One study found that quercetin produced

this effect against herpes simplex, polio virus, flu virus, and respiratory

viruses.17,18 However, none of this research tells us whether humans taking

quercetin supplements can hope for the same benefits. Much more research needs

to be done on the use of quercetin for these conditions.

Safety Issues

Quercetin appears to be quite safe. However, at one point concerns were raised

that it might cause cancer. Quercetin " fails " a standard laboratory test called

the Ames test, which is designed to identify chemicals that might be

carcinogenic. However, a bad showing on the Ames test does not definitely mean a

chemical causes cancer. Other evidence suggests that quercetin does not cause

cancer, and may in fact help prevent cancer.19,20,21

 

However, one highly preliminary study suggests that quercetin combined with

other bioflavonoids in the diet of pregnant women might increase the risk of

infant leukemia.22

 

Maximum safe dosages for young children, women who are pregnant or nursing, or

those with serious liver or kidney disease have not been established.

 

References

 

1. Ogasawara H, Middleton E Jr. Effect of selected flavonoids on histamine

release (HR) and hydrogen peroxide (H2O2) generation by human leukocytes

[abstract]. J Allergy Clin Immunol. 1985;75(suppl):184.

 

2. Middleton E Jr. Effect of flavonoids on basophil histamine release and other

secretory systems. Prog Clin Biol Res. 1986;213:493-506.

 

3. Yoshimoto T, Furukawa M, Yamamoto S, et al. Flavonoids: potent inhibitors of

arachidonate 5-lipoxygenase. Biochem Biophys Res Commun. 1983;116:612-618.

 

4. Shoskes DA, Zeitlin SI, Shahed A, et al. Quercetin in men with category III

chronic prostatitis: a preliminary prospective, double-blind, placebo-controlled

trial. Urology. 1999;54:960-963.

 

5. Rodriguez LV, Janzen N, Raz S, et al. Treatment of interstitial cystitis with

a quercetin containing compound: a preliminary, double-blind placebo control

trial. Presented at: American Urological Association 2001 Annual Meeting; June

2-7, 2001; Anaheim, Calif.

 

6. Constant J. Alcohol, ischemic heart disease, and the French paradox. Coron

Artery Dis. 1997;8:645-649.

 

7. Hayek T, Fuhrman B, Vaya J. 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;17:2744-2752.

 

8. Frankel EN, Waterhouse AL, Kinsella JE. Inhibition of human LDL oxidation by

resveratrol. Lancet. 1993;341:1103-1104.

 

9. Alliangana DM. Effects of beta-carotene, flavonoid quercetin and quinacrine

on cell proliferation and lipid peroxidation breakdown products in BHK-21 cells.

East Afr MedJ. 1996;73:752-757.

 

10. Keli SO, Hertog MG, Feskens EJ, et al. Dietary flavonoids, antioxidant

vitamins, and incidence of stroke: the Zupthen study. Arch Intern Med.

1996;156:637-642.

 

11. Balasubramanian S, Govindasamy S. Inhibitory effect of dietary flavonol

quercetin on 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch

carcinogenesis. Carcinogenesis. 1996;17:877-879.

 

12. Cross HJ, Tilby M, Chipman JK, et al. Effect of quercetin on the genotoxic

potential of cisplatin. Int J Cancer. 1996;66:404-408.

 

13. Hoffman R, Graham L, Newlands ES. Enhanced anti-proliferative action of

busulphan by quercetin on the human leukaemia cell line K562. Br J Cancer.

1989;59:347-348.

 

14. ElAttar TM, Virji AS. Modulating effect of resveratrol and quercetin on oral

cancer cell growth and proliferation. Anticancer Drugs. 1999;10:187-193.

 

15. Yoshida M, Yamamoto M, Nikaido T. Quercetin arrests human leukemic T-cells

in late G1 phase of the cell cycle. Cancer Res. 1992;52:6676-6681.

 

16. Varma SD, Mizuno A, Kinoshita JH. Diabetic cataracts and flavonoids.

Science. 1977;195:205-206.

 

17. Kaul TN, Middleton E Jr, Ogra PL. Antiviral effect of flavonoids on human

viruses. J Med Virol. 1985;15:71-79.

 

18. Musci I, Pragai BM. Inhibition of virus multiplication and alteration of

cyclic AMP level in cell cultures by flavonoids. Experientia. 1985;41:930-931.

 

19. Stavric B. Quercetin in our diet: from potent mutagen to probable

anticarcinogen. Clin Biochem. 1994;27:245-248.

 

20. Friedman M, Smith GA. Factors which facilitate inactivation of quercetin

mutagenicity. Adv Exp Med Biol. 1984;177:527-544.

 

21. ElAttar TM, Virji AS. Modulating effect of resveratrol and quercetin on oral

cancer cell growth and proliferation. Anticancer Drugs. 1999;10:187-193.

 

22. Strick R, Strissel PL, Borgers S, et al. Dietary bioflavonoids induce

cleavage in the MLL gene and may contribute to infant leukemia. Proc Natl Acad

Sci. 2000;97:4790-4795.

 

Reviewed By HealthGate CAM Medical Review Board

Copyright 2003 HealthGate Data Corp. All rights reserved

 

 

First published May 12, 2000

Last updated March 1, 2002