What does selenium do?

Selenium activates an antioxidant enzyme called glutathione peroxidase, which may help protect the body from cancer. Selenium has also induced “apoptosis” (programmed cell death) in cancer cells. A recent double blind study following over 1,300 people found that those given 200 mcg of yeast-based selenium per day for seven years had a 50% drop in the cancer death rate compared with the placebo group. Another recent trial found that men exposed to the most dietary selenium (as indirectly measured by toenail selenium levels) developed 65% less advanced prostate cancer than men with the lowest levels of selenium.

Selenium is also essential for healthy immune functioning. As a result, selenium supplements have reduced the incidence of hepatitis in deficient populations. Even in a nondeficient population of elderly people, selenium supplements have been found to stimulate the activity of white blood cells—primary components of the immune system. Selenium is also needed to activate thyroid hormones.

Although details are not understood, selenium supplements have partially normalized the actions of sperm cells in infertile men in double blind research.

Where is selenium found?

Brazil nuts are the best source of selenium. Yeast, whole grains, and seafood are also good sources.

Who is likely to be deficient in selenium?

While most people probably don’t take in enough selenium, gross deficiencies are rare in Western countries. Soils in some areas are selenium deficient, and people who eat foods grown primarily on selenium-poor soils are at risk for deficiency. People with AIDS have been reported to be depleted in selenium. Similarly, limited research has reported an association between heart disease and depleted levels of selenium.

How much is usually taken?

An adult intake of 200 mcg of selenium per day is recommended by many nutritionally oriented doctors.

Are there any side effects or interactions?

Selenium is safe at the level people typically supplement (200 mcg); however, taking more than 1,000 mcg of selenium per day can cause loss of fingernails, skin rash, and changes in the nervous system. In the presence of iodine-deficiency induced goiter, selenium supplements have been reported to exacerbate low thyroid function.

Information on this site is provided for informational purposes and is not meant to substitute for the advice provided by a licensed physician. You should not use the information on this website for diagnosing or treating a health problem or disease, or prescribing any medication.