Diet - selenium

Alternative names
Selenium in diet

Definition
Selenium is an essential trace element. It is an integral part of enzymes, which are critical for control of the numerous chemical reactions involved in brain and body functions.

Function

Selenium has a variety of functions. The main one is its role as an antioxidant in the enzyme selenium-glutathione-peroxidase. This enzyme neutralizes hydrogen peroxide, which is produced by some cell processes and would otherwise damage cell membranes.

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.

Selenium may assist in the synthesis of protein, in growth and development, and in fertility, especially in men. It 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

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

Keshan disease is caused by a deficiency of selenium. This leads to an abnormality of the heart muscle. Keshan disease claimed the lives of many children in China until the relationship to selenium was discovered and selenium supplements were provided.

Cattle grazing in selenium-rich soil have shown toxicity caused by increased levels of selenium. The cattle developed muscle, visual, and heart problems.

The amount of selenium that would 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

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

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

Evidence exists that selenium may play a role in cancer prevention, but better studies are needed. There have been mixed results regarding selenium’s impact on cardiovascular disease.

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