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. There is no recommended daily allowance for selenium. The suggested intake by nutrition experts is 50 to 200 micrograms, which the average diet in the U.S. usually provides.
Selenium is often available in multivitamin and mineral supplements.
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.