Quercetin is a naturally occurring bioflavonoid found in fruits, vegetables, leaves and grains. Quercetin possesses powerful antioxidant properties and, like other bioflavonoids, has the ability to stabilize cell membranes.
Clinical studies have shown that quercetin has the ability to support immune function as well as healthy histamine levels. Since flavonoids help protect and enhance vitamin C, quercetin is often taken with vitamin C. Moreover, quercetin supplements may support prostate health.
High concentrations of quercetin can be found in red onions, green tea, grapes, red wine, apples, capers, tomatoes, and black tea. Smaller amounts are found in leafy green vegetables, beans, honey and a number of berries including, raspberry, lingonberry, and cranberry. Quercetin is often used as an ingredient in supplements, beverages or foods.
Quercetin may have anti-inflammatory and antioxidant properties, and it is being investigated for a wide range of potential health benefits. It has demonstrated significant anti-inflammatory activity by inhibiting both manufacture and release of histamine and other allergic and inflammatory mediators. In addition, it exerts potent antioxidant activity and vitamin C -sparing action.
Quercetin may have inhibitory properties against cancer, prostatitis, heart disease, cataracts, and respiratory diseases, such as bronchitis, allergies and asthma. It may also help to reduce blood pressure. Some doctors recommend 200–500 mg of quercetin taken two to three times per day.
Many quercetin supplements contain bromelain in their formulations. An enzyme complex derived from the pineapple stem, Bromelain may enhance quercetin absorption, increasing the effects of quercetin and promoting additional benefits.