DEFINITION

Quercetin is an antioxidant that belongs to the family of chemicals called flavonoids.

DESCRIPTION

Quercetin is classed as a type of 'phyto-oestrogen', which are oestrogen-like chemicals that occur in some plants. Quercetin is a powerful, natural antihistamine, which means that it opposes the actions of the histamines in the body. Histamines are responsible for allergic and inflammatory reactions. Sinusitis and allergic rhinitis are two medical conditions where there is inflammation and allergy caused by histamine. Quercetin reduces the 'stickiness' of platelets and reduces the formation of blood clots. Quercetin is a natural antioxidant that may reduce the risks of certain cancers developing. Quercetin prevents damage to blood vessels by certain forms of cholesterol and other chemicals produced by the body. People with diabetes are at higher risk of blood vessel damage from free radicals. A high dietary intake of Quercetin reduces the number of free radicals in people with type II diabetes. Quercetin also prevents the chemical sorbitol being formed, which is linked with many complications of diabetes such as cataracts.

DEFICIENCY

The effects of Quercetin deficiency are not known.

SOURCES

Quercetin can be found in onions, apples, green and black tea and in smaller amounts in leafy green vegetables and beans.

DOSAGE

There is no fixed dietary recommendation for Quercetin intake. Quercetin supplements appear to be safe but the health effects of large doses over long periods of time are not known. Dietary supplements of Quercetin usually recommend a dosage of about 400 mg two to three times per day.

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