Background

• Quercetin is a major flavonol, one of the almost 4,000 flavonoids (antioxidants) that occur in foods of plant origin, such as red wine, onions, green tea, apples, berries, and Brassica vegetables (cabbage, broccoli, cauliflower, turnips). Quercetin is also found in Gingko biloba, St. John's wort, and American elder.
• Quercetin and rutin (another flavonol) are used in many countries as vasoprotectants (protects blood vessels) and are ingredients of numerous multivitamin preparations and herbal remedies. They occur mainly as glycosides, which means they are linked with various sugars. However, the ability of the body to absorb these compounds is questionable.
• Quercetin and other flavonols have a wide variety of biological effects, but the scientific evidence for use in the prevention or treatment of disease is weak. Quercetin has been considered as a therapy for cardiovascular diseases, high cholesterol, diabetic cataracts, inflammation, ischemic injury, chronic prostatitis, chronic venous insufficiency, gastrointestinal ulceration, hepatitis, allergies, asthma, viral infections, and hay fever.
• Review of the literature shows that there have been several studies on the association of quercetin and with the risk reduction for coronary heart disease and stroke, high blood pressure, cancers, and a few studies on other medical conditions. However, there is a lack of strong evidence to support any of these conditions.

References

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