quercetin

Introduction

Quercetin belongs to a class of water-soluble plant pigments called flavonoids.
Where is it found?
Quercetin can be found in onions, apples, green tea, and black tea. Smaller amounts are found in leafy green vegetables and beans.
Quercetin has been used in connection with the following conditions (refer to the individual health concern for complete information):
Science Ratings - Health Concerns
*** - Prostatitis (nonbacterial prostatitis, prostadynia)
* - Allergies
* - Asthma

* - Atherosclerosis
* - Capillary fragility
* - Cataracts
* - Childhood diseases
* - Edema (water retention)
* - Gout
* - Hay fever
* - Peptic ulcer
* - Retinopathy
* - Type 1 diabetes
* - Type 2 diabetes
*** - Reliable and relatively consistent scientific data showing a substantial health benefit.

** - Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.

* - For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.
Who is likely to be deficient?
No clear deficiency of quercetin has been established.
How much is usually taken?
Some doctors recommend 200–500 mg of quercetin taken two to three times per day. Optimal intake remains unknown.
Are there any side effects or interactions?
No clear toxicity has been identified. Early quercetin research suggested that large amounts of quercetin could cause cancer in animals.1 Most,2 3 4 but not all,5 current research finds quercetin to be safe or actually linked to protection from cancer.
Quercetin has been shown to cause chromosomal mutations in certain bacteria in test tube studies.6 Although the significance of this finding for humans is not clear, some doctors are concerned about the possibility that birth defects could occur in the offspring of people supplementing with quercetin at the time of conception or during pregnancy.
Since flavonoids help protect and enhance vitamin C, quercetin is often taken with vitamin C.

Drug Interactions
Certain medicines interact with quercetin: Some interactions may increase the need for quercetin (+), other interactions may be negative (-) and indicate quercetin should not be taken without first speaking with your physician or pharmacist, others may require further explanation (?). Refer to the individual drug article for specific details about an interaction.
Note: The following list only includes the generic or class name of a medicine. To find a specific brand name, use the Medicines index.
Cyclosporine (?)
Estradiol (-)
Felodipine (-)

Source: www.cncahealth.com