Quercetin is a flavonoid antioxidant found in many fruits and vegetables. It serves a variety of important health effects and has been used successfully for its cholesterol-lowering, anti-cancer and anti-inflammatory benefits. Aside from dietary sources, you can obtain quercetin in supplement form and it can often be found in formulas together with other anti-inflammatory compounds, such as bromelain, grape seed and green tea. Consult your physician before taking any supplement.
Quercetin prevented progression of chronic obstructive pulmonary diseases, COPD, in a study conducted at the Department of Pediatrics and Communicable Diseases, University of Michigan. In the study, researchers gave laboratory animals 0.5 milligrams per day for 10 days and noted improved lung elasticity, decreased oxidation and decreased inflammation. Quercitin also decreased levels of tissue-damaging enzymes known as matrix metalloproteinases. The study was published in the September 2010 issue of the journal "Respiratory Research."
Researchers at the College of Veterinary Medicine, Chungbuk National University, Korea, reported that quercetin doses of 10 milligrams per kilogram of body weight — which is a higher than normal for human use — produced anti-inflammatory effects in laboratory animals. Scientists administered the high dose of quercetin using a tube-feeding method called gavage once per day for three days, as a way to saturate the tissues. Quercetin exerted its effects, in part, by inhibiting nitric oxide production in white blood cells known as macrophages, reducing nitric oxide levels by half. The antioxidant also reduced the inflammatory response involving neutrophils, another type of white blood cell. Researchers concluded significant anti-inflammatory potential for quercetin in this preliminary animal study, published in the September 2008 issue of the "Journal of Veterinary Science."
Quercetin has been used to reduce inflammation in prostate conditons for its anti-inflammatory and anti-testosterone effects, according to Jeannette Potts, M.D., in her book "Genitourinary Pain and Inflammation: Diagnosis and Management." The antioxidant decreases levels of inflammatory prostaglandins and increases levels of prostatic endorphins — natural pain-relieving molecules. Potts recommends doses of 500 milligrams twice per day. Combine quercetin with the anti-inflammatory enzyme bromelain and papain to improve quercetin absorption.
Quercetin inhibits bacterial infections, writes David Rakel, M.D., in his book "Integrative Medicine." Infections cause inflammation by activating your immune system, and inflammation is a part of any immune reaction. Because of its antibacterial effects, quercetin helps reduce both infection and inflammation. Take 200 to 400 milligram doses 20 minutes before meals, three times per day.
You may easily obtain healthy doses of quercetin from your diet. Good food sources of quercetin include onions, parsley, sage tomatoes and citrus fruits. Quercetin is also found in tea and apples and is present in high concentrations in some berries, such as lingonberries, which contain 74 to 146 milligrams per kilogram. Black currants contain 52 to 122 milligramss per kilogram, and bilberries provide 30 milligrams per kilogram of quercetin.
Side effects of quercetin are rare but may include headache or upset stomach, according the the University of Maryland Medical Center. Avoid quercetin if you are pregnant or breastfeeding or if you have kidney disease. Doses of more than 1 gram per day have been associated with kidney damage. Quercetin can interfere with some prescription drugs. Consult your doctor about using quercetin if you take blood thinners, cancer chemotherapy drugs, corticosteroids or immune suppressing drugs.