Quercetin belongs to a class of plant-based chemical pigments known as flavonoids that give color to fruits, vegetables and flowers. It can be obtained from foods such as apples, onions, red wines, parsley and tea, and has been used traditionally to treat a variety of conditions. Quercetin supplements are available at most pharmacies without a prescription. However, they have been associated with some side effects and should be used only under the supervision of a doctor.
Benefits
Quercetin possesses significant antioxidant activity and helps neutralize unstable free radicals that are formed as a result of various metabolic processes. The free radicals interact with cellular components and cause cell damage, leading to a variety of conditions including cancer and heart disease.
The University of Maryland Medical Center suggests that quercetin may prevent cardiovascular diseases by inhibiting plaque formation in the blood vessels. It may also reduce symptoms in patients suffering from intestinal cystitis. Quercetin has been shown to reduce inflammation and allergy by suppressing the enzymes involved in the formation of chemicals and markers that lead to allergy symptoms such as runny nose, itchy eyes and certain arthritis symptoms, states Memorial Sloan-Kettering Cancer Center. Intake of quercetin may be associated with lower risk of breast, lung, pancreatic and other types of cancers, although more research is needed to ascertain quercetin's possible benefits, notes the American Cancer Society. A study published in the February 2010 edition of the "International Journal of Sport Nutrition and Exercise Metabolism" states that quercetin may help increase endurance capacity and athletic performance.
Dosage
Along with fruits, vegetables, olive oil and red wine, quercetin can also be obtained from supplements available in tablet and capsule forms. The supplements contain quercetin in combination with bromelain, an enzyme found in pineapple. The efficacy and safety of quercetin in children has not been determined. However, UMMC reports that about 100 to 250 mg of the supplement, three times a day may be enough for general supplementation. UMMC also recommends 250 to 600 mg of the pigment divided in several doses to treat allergies and 500 mg twice daily for other conditions such as intestinal cystitis. It is, however, best to talk to a doctor to determine a dose that is right for you before using quercetin.
Side Effects
Quercetin obtained from dietary sources is safe. The supplements may sometimes be associated with mild side effects such as headache and upset stomach. Women who are pregnant or nursing and individuals with kidney diseases should avoid these supplements. It may also interfere with certain blood thinning and corticosteroid medications.
Precautions
Always talk to a doctor before using quercetin supplements to avoid possible adverse reactions and drug interactions. It is also important to ascertain the purity and quality of quercetin supplements before using them.
References
- University of Maryland Medical Center: Quercetin
- Memorial Sloan-Kettering Cancer Center: Quercetin
- American Cancer Society: Quercetin
- "International Journal of Sport Nutrition and Exercise Metabolism"; The Dietary Flavonoid Quercetin Increases VO(2max) and Endurance Capacity.; J.M. Davis, et al.; February 2010
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