The Health Benefits of Quercetin

Quercetin is a chemical found naturally in a number of foods including apples, onions, teas, berries, and red wine. This flavonoid is also found in some herbs such as ginkgo biloba and St. John's wort.

Quercetin acts as an antioxidant, scavenging free radicals, chemical by-products known to harm cell membranes and damage DNA. Available as a dietary supplement, quercetin also possesses antihistamine and anti-inflammatory properties.

In alternative medicine, quercetin is said to help with the following conditions:

• Allergies
• Cardiovascular disease
• Inflammation
• Colds

So far, scientific support for the benefits of quercetin is lacking. However, there are some studies that have investigated how the compound interacts with these conditions.

Allergy Relief

Quercetin is thought to prevent the release of histamine from certain immune cells. (An inflammatory chemical, histamine is involved in allergic symptoms such as sneezing and itching.)

Although lab experiments suggest that quercetin may help fight allergies, a 2002 report cautions that "there are no good clinical research data on the use of quercetin" for patients with allergic rhinitis.

High Blood Pressure

In a 2007 study of 41 adults, researchers found that taking 730 mg of quercetin daily for 28 days reduced blood pressure in people with hypertension. However, blood pressure was not altered in study members with prehypertension—a condition marked by slightly elevated blood pressure.

Athletic Endurance

Quercetin may be no better than a placebo when it comes to enhancing athletic performance, according to a 2009 study of 30 healthy men. For the study, some participants consumed a sports drink containing 250 mg of quercetin four times a day for up to 16 days, while a placebo group drank the same beverage without quercetin. Results showed that the short-term quercetin supplementation failed to improve cycling performance and the ability of muscles to synthesize energy.

Chronic Pelvic Pain Syndrome

Findings from a randomized, double-blind, placebo-controlled trial indicate that use of quercetin supplements may improve symptoms in most men with chronic pelvic pain syndrome. The study involved 30 men with prostatitis, a condition that involves inflammation of the prostate gland.

Cancer

Studies on cell cultures have shown that quercetin may help slow the growth of some types of cancer cells. Some animal-based research indicates that quercetin may protect against certain types of cancer, such as colon cancer. However, since there is currently a lack of human studies on quercetin's cancer-fighting effects, it's too soon to tell whether quercetin might play a significant role in cancer prevention.

For now, the American Cancer Society states that it is "reasonable to include foods that contain quercetin as part of a balanced diet with an emphasis on fruits, vegetables, legumes, and whole grains."

Quercetin is generally well-tolerated when used in appropriate amounts. If used intravenously, patients may experience flushing, sweating, nausea, vomiting, dyspnea, and pain at the injection site. There are also reports of tingling in the arms and legs and headaches experienced by patients taking it orally. Very high doses might cause kidney damage

Supplements haven't been tested for safety and due to the fact that dietary supplements are largely unregulated, the content of some products may differ from what is specified on the product label. Also keep in mind that the safety of supplements in pregnant women, nursing mothers, children, and those with medical conditions or who are taking medications has not been established.

Under the care of medical supervision, quercetin has been safely used in amounts up to 500 mg twice daily for 12 weeks. There is not enough evidence to know if it is safe for long-term use.

The appropriate dose for you may depend on factors including your age, gender, and medical history. Speak to your healthcare provider to get personalized advice if you choose to take this supplement.

Food sources of quercetin include teas, onions, apples, buckwheat, and pau d'arco. When taking quercetin in supplement form, it may be beneficial to choose a product that also contains papain and/or bromelain. These are plant-derived enzymes (fruit extracts) shown to increase the intestine's absorption of quercetin.

Due to the lack of supporting research, it's too soon to recommend quercetin for any health purpose. If you're considering using it, consult your primary care provider first. Self-treating a condition and avoiding or delaying standard care may have serious consequences.