Selenium is a trace element that functions as part of the enzyme glutathione peroxidase, a vital antioxidant system that protects cell membranes.

Selenium deficiency has been linked to Kashin-Beck's disease and Keshan disease. Selenium is found mostly in grains and seeds, though their exact selenium content depends on the amount of selenium in the soil in which they are grown. Seafood, kidney, liver, and other meats are also high in selenium.

Recommended Dietary Allowances for Selenium:

No adverse effects have been observed for selenium intakes under 750 mcg/d, but consumption of very large amounts can lead to negative effects on hair, nails, skin, and teeth.