Quercetin quer·ce·tin (kwr-s-tn) is a plant-derived , specifically a , used as a . Laboratory studies show it may have anti-inflammatory and antioxidant properties , and it is being investigated for a wide range of potential health benefits.
Quercetin has been shown to increase energy expenditure in rats, but only for short periods (fewer than 8 weeks) . Effects of quercetin on exercise tolerance in mice have been associated with increased mitochondrial biogenesis.
The American Cancer Society says that while quercetin "has been promoted as being effective against a wide variety of diseases, including cancer," and "some early lab results appear promising, as of yet there is no reliable clinical evidence that quercetin can prevent or treat cancer in humans." In the amounts consumed in a healthy diet, quercetin "is unlikely to cause any major problems."
High dietary intake of fruits and vegetables is associated with reduction in cancer, and some scientists suspect quercetin may be partly responsible. Research shows that quercetin influences cellular mechanisms in vitro and in animal studies, and there is limited evidence from human population studies that quercetin may reduce the risk of lung cancer.
Some researchers believe quercetin should not be used by healthy people (for prevention) until it can be shown that quercetin doesn't itself cause cancer. In laboratory studies of cells (), quercetin produces changes that are also produced by compounds that cause cancer (), but these studies don't report increased cancer in animals or humans. The U.S. Food and Drug Administration has not approved any health claims for quercetin. There is current early-stage clinical research on quercetin addressing safety and efficacy against , and absorption in and (February 2009).
Quercetin is the form of a number of other flavonoid , such as and , found in fruit, and onions. Quercetin forms the and together with and , respectively. Quercetin is classified as (no evidence of in humans).