Credit zinc for helping the immune system

This essential mineral is found in oysters, red meat, beans and many other foods. It gained fame as a supplement in the 1990s for its purported ability to shorten the duration of a cold.

Uses: Important to growth during pregnancy, childhood and adolescence. Also supports the immune system, promotes wound healing and helps maintain the sense of taste and smell. Zinc deficiencies develop in some people, such as alcoholics. Vegetarians can also become low in zinc.

Dose: Recommended dietary allowances -- including upper limits -- have been set for infants, children and adults. Supplement doses typically range from 10 milligrams to 23 milligrams.

Precautions: Zinc can be toxic in high amounts (150 milligrams or more daily).

Research: Zinc supplements can promote wound healing but only among people who are zinc deficient.

Studies are mixed on whether taking zinc acetate lozenges (usually at doses of about 80 milligrams per day) can shorten the duration of a cold. It may depend on whether a particular supplement’s formula can deliver zinc ions directly to the respiratory cells that harbor the infection.

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Dietary supplement makers are not required by the U.S. government to demonstrate that their products are safe or effective. Ask your health provider for advice on selecting a brand.