definition
Quercetin is a bioflavonoid that gives pigment to many plants and herbs. The substance has been shown to exert anti-inflammatory, antihistamine, antioxidant, and anticancer properties.

clinical applications
Allergies and Asthma. In a Japanese study published in the Journal of Allergy and Clinical Immunology, quercetin was effective against symptom-causing histamine activity in mast cells. The study found that histamine release was reduced 46 to 96 percent by the nutraceutical. Additional studies have found high intakes of apples rich in quercetin and other flavonoids lower the risk of certain respiratory diseases such as asthma, bronchitis, and emphysema.

Arthritis. In an in-vitro study published in the Journal of Rheumatology, researchers pretreated human synovial cells with quercetin for seven hours. Inflammation of the synovial cell is the primary cause of pain associated with rheumatoid arthritis. The cells then were incubated to induce production of proinflammatory agents. Results showed quercetin reduced stimulation of these agents in a dose-dependent manner, meaning it inhibited inflammation.

Anticancer. There appears to be an inverse relationship between dietary flavonoid intake and incidence of cancer. In a 24-year study of nearly 10,000 men and women ages 15 to 99 who were cancer free at the beginning of the study, flavonoid consumption of 4.15 mg per day resulted in a 20 percent reduction in overall cancer risk, compared with lower consumption levels. Most striking was a 46 percent decrease in lung cancer risk.

Prostate Health. In a randomized, double-blind trial, 30 men with chronic prostatitis were given either 500 mg quercetin supplements or placebo twice daily for one month. The investigators found that 67 percent of those in the treatment group experienced at least a 25 percent improvement of symptoms as compared to only 23 percent of patients in the placebo group experiencing similar improvement.

Heart Disease. The findings of The Rotterdam Study, published in the American Journal of Clinical Nutrition, indicate that quercetin and other flavonoids may help prevent heart attacks. The study examined the tea-drinking habits and dietary flavonoid intakes of nearly 5,000 adults in Holland. Black tea’s high flavonoid concentration appeared to reduce the risk of heart attack in tea drinkers. What’s more, there seems to be an especially strong connection between high intake of dietary flavonoids and reduced risk of fatal heart attack in women. Most likely this protection is related to the flavonoids’ role as phytoestrogens (i.e., plant estrogens), which can offer heart-protective benefits similar to those of soy.

recommendations
A dose of 200 to 500 mg of quercetin taken two to three times daily is generally recommended. Consult your health practitioner to determine the precise dose for your health needs.

safety
Quercetin appears to be safe. However, according to Mark Stengler, ND, people who are sensitive to citrus have reported reactions when taking quercetin in a formula with vitamin C or citrus bioflavonoids.

conclusions
There are two major benefits of consuming the many fruits and vegetables that contain quercetin or taking quercetin supplements. In the short term, quercetin may help relieve congestion, itchy eyes, and other pesky allergy symptoms. Over time, taking this valuable substance might help prevent life-threatening conditions, such as cancer and heart disease.