Quercetin is a flavonoid that gives color to some fruits and vegetables, including apples, citrus fruits, beans, bilberries, blackberries, blueberries, dark cherries, grapefruit, grapes, leafy green vegetables, onions and parsley. Wine, tea, buckwheat and olive oil also contain quercetin. Quercetin functions in a number of ways in the body, and may provide health benefits.
Function
Quercetin functions as an antioxidant, an anti-inflammatory and an antihistamine, according to the University of Maryland Medical Center. Quercetin may also have anti-cancer and anti-allergy effects, but research in these areas is still preliminary, so don't rely on quercetin in place of conventional treatments for these conditions.
Dosage
The dosage for quercetin depends on the condition you are trying to treat. For general use, a dose between 100 mg and 250 mg taken three times a day is common. Divided doses totaling between 250 mg and 600 mg per day may help with allergies and 500 mg of quercetin taken twice a day may help with prostatitis or interstitial cystitis, notes the University of Maryland Medical Center.
Safety
Do not exceed 1 mg per day of quercetin supplements without the advice of your doctor, as doses this high may cause damage to the kidneys over time. Quercetin side effects include upset stomach, nausea and headaches. If you are taking blood thinners, chemotherapy medication, cyclosporine or corticosteroids, you should not take quercetin supplements, as these medications may interact, causing harmful effects.
Considerations
The amount of quercetin you get from food is safe, but you should speak with your doctor before taking supplemental quercetin to make sure it is safe for you and to determine the appropriate dose. Safe doses for children, pregnant women, breastfeeding women and people with kidney or liver disease have not been determined, so these people should not take supplemental quercetin.
