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What Does Quercetin Do?

According to the American Cancer Society, quercetin is a naturally occurring substance belonging to a family of nutrients known as flavonoids. Flavonoids are known for their antioxidant properties and have been praised for all kinds of positive health results, from allergy relief to cancer prevention. While, as the World's Healthiest Foods website (WHFoods) indicates, flavonoids were originally referred to as "Vitamin P," they are actually plant pigments.

  1. Function

    • WH Foods indicates that the function of flavonoids is primarily as an antioxidant. Antioxidants neutralize free radicals--cells, cell fragments, and substances that have been oxidized to such an extent that they can become harmful to other cells in the body--as well as protect cells from further damage by those same free radicals. Flavonoids, including quercetin, can enhance the body's absorption and use of vitamin C. Likewise, vitamin C actually improves the efficacy of flavonoids, as well.

    Benefits

    • The American Cancer Society cites the Physicians Desktop Reference on its website, listing quercetin as a substance that is useful in treating allergies and asthma due to antihistamine and anti-inflammatory properties. Rx List, a website geared toward providing prescription and drug information, cites a study published in Urology (1999) shows that quercetin may also be helpful in the prevention or elimination of prostate inflammation.

    Theories/Speculation

    • The American Cancer Society indicates that - due to its ability to cause genetic mutations in bacteria - it was originally thought that quercetin may have been a carcinogen (cancer causing agent). However, in their article on quercetin published in 2008, the ACS also states that the animal and cell-structure studies cited by them indicate the potential use of quercetin for cancer prevention or treatment. Many of these animal studies have actually been very promising, but further studies are needed to determine the effectiveness of quercetin in treating cancer in humans.

    Misconceptions

    • There does not appear be sufficient evidence for beneficial effects of quercetin on atherosclerosis, viral infections, chronic fatigue or gastrointestinal ulcers. While Rx List indicates that there may not be conclusive evidence of its use as an antihistamine, more recent studies referenced by the American Cancer Society indicate that this is not the case (as stated above).

    Sources

    • As is the case with other flavonoids, quercetin can be found in many plant sources. Among these are apples, onions, red wine and some types of teas. While quercetin is definitely beneficial to the human body, the American Cancer Society does say that a diet rich in all kinds of flavonoids (i.e., that contains a high amount of fruits and vegetables) will be more beneficial to the body than any singular antioxidant or flavonoid. Quercetin can also be found in capsules as a dietary supplement, though no standard dosing measurements exist for it.

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