quercetin

Reduce cancer risk. Quercetin may help reduce the risk of developing cancer. In one study, lung cancer was 58% lower among people who ate the most apples compared to those who ate the fewest. Quercetin and other flavonoids have also been shown to help reduce the risk of stomach, pancreatic, and breast cancer.

Prevent heart attack. One cause of heart disease is the overgrowth of smooth muscle cells in artery walls, a key component in the development of atherosclerosis. As it does with cancer cells, there is now evidence that quercetin functions in a similar way to stop the overgrowth of cells that harm the heart. A 2002 study in the journal Surgery reported that in laboratory tests, quercetin arrested the development of vascular smooth muscle cells by locking them in a "no-growth" state. This may be why the Rotterdam Study found that quercetin contributes to reduced heart attack risk.

Stave off cataracts. A lifetime of unprotected sun exposure can damage the eyes as well as the skin. It happens so gradually that many people aren't aware they're developing cataracts. Ultraviolet (UV) rays, particularly the burning UVB rays, damage proteins in the lens of the eye, causing them to clump together in a whitish cloud. Cigarette smoking and a deficiency in antioxidant vitamins are other major causes of cataracts. Research indicates that quercetin blocks an enzyme that leads to accumulation of sorbitol, a type of sugar that contributes to cataract formation.

Control asthma. Quercetin may be useful in relieving asthma (and possibly hay fever and sinusitis) as a result of its ability to reduce inflammation in the airways and prevent the release of histamine (which causes congestion). It appears to block allergic reactions to pollen as well.

Maintain health when suffering from Crohn's disease. Quercetin, a natural anti-inflammatory, may be helpful in countering the hallmark of Crohn's disease: chronic inflammation of the gastrointestinal tract. Crohn's manifests itself as abdominal pain, fever, diarrhea, and weight loss. The small intestine is primarily affected, and the patient develops real problems in absorbing important nutrients. Conventional physicians use the anti-inflammatory drugs sulfasalazine and steroids to reduce the inflammation; taking quercetin is one (natural) way to supplement the actions of these drugs.

To prevent recurrent gout attacks. Taken with cherry fruit extract (as well as fresh or canned cherries), vitamin C, and possibly fish oils, quercetin may do the trick in forestalling acute attacks by lowering elevated uric acid levels--the cause of the painful attacks. The combination can be taken on a long-term basis.

Speed up healing of recurrent heartburn, or gastroesophageal reflux disorder (GERD). As a flavonoid, quercetin functions as a natural anti-inflammatory, antihistamine, and possibly an inhibitor of Helicobacter pylori, the bacterium associated with stomach ulcers, which can cause recurrent heartburn. If your heartburn symptoms are persistent, you may want to take a daily combination of quercetin and flavonoids to accelerate healing.

Forms

tablet
capsule
Dosage Information

Special tips:
--Quercetin is available in combination with another flavonoid, rutin, which is derived from buckwheat.

To reduce cancer risk: Take 125-250 mg daily.

To prevent heart attack: Take 125-250 mg daily.

To prevent cataracts: Take 125-250 mg daily.

For asthma: Take 250-500 mg 3 times a day.

For Crohn's disease: Take 400 mg 3 times a day.

For recurrent gout attacks: Take 500 mg twice a day.

For heartburn: Take 500 mg three times a day of quercetin or mixed bioflavonoids (with or without added bromelain).

Guidelines for Use

For those who cannot drink red wine for its heart-protecting benefits, quercetin capsules may constitute an effective alternative.

When possible, take quercetin in combination with vitamin C; the flavonoid enhances the vitamin's effect.

General Interaction

If you take hormone replacement therapy (HRT), quercetin may increase estradiol and reduce the effectiveness other forms of estrogen. However, the laboratory study that indicated this could be a problem involved much higher levels of quercetin than that found in most dietary supplements.

Don't take quercetin if you take the calcium channel blocker felodipine, for high blood pressure. In test tubes studies, quercetin inhibited enzymes that break down felodipine; in theory this could increase blood levels of the drug and lead to unwanted side effects.

Possible Side Effects

There are no known side effects associated with quercetin in supplement form.

Cautions

There are no known cautions associated with quercetin.