Definition
Selenium is an essential trace element. It is an integral part of enzymes.

Alternative Names
Diet - selenium

Function
Selenium has a variety of functions. The main one is its role as an antioxidant in the enzyme selenium-glutathione-peroxidase.

Selenium also seems to stimulate antibody formation in response to vaccines. It also may provide protection from the toxic effects of heavy metals and other substances. It may assist in the synthesis of protein, in growth and development, and in fertility, especially in men. Selenium has been shown to improve the production of sperm and sperm motility.

Food Sources
Fish, shellfish, red meat, grains, eggs, chicken, liver, and garlic are all good sources of selenium. The amount of selenium in vegetables is dependent on the selenium content of the soil. Brewer's yeast and wheat germ, both considered health foods, are also good sources of selenium.

Side Effects
Keshan disease has been documented as being caused by a deficiency of selenium. It causes an abnormality of the heart muscle, and it claimed the lives of many children in China until the relationship to selenium was discovered and selenium supplements were provided.

Selenium deficiency may also occur in patients fed intravenously for long periods of time.

Increased intake of selenium can lead to toxicity in cattle grazing in selenium-rich soil. The cattle demonstrate muscle, visual and heart problems.

The amount of selenium required to cause toxicity in humans is not known. Excess selenium intake can cause problems with the strength of teeth and the tooth enamel. Other problems may include loss of teeth, hair, and nails. Skin inflammation, nausea, and fatigue can also occur.

Recommendations
The suggested intake by nutrition experts is 50 to 200 micrograms for adults, which the average diet in the U.S. usually provides. Selenium is often available in multi-vitamin and mineral supplements.

Specific recommendations for each nutrient depend on age, gender, and other factors (such as pregnancy). The U.S. Department of Agriculture has a PDF file that lists these recommendations.