Selenium's role in influencing antioxidant activity is well-known. It is a vital component of an antioxidant enzyme known as glutathione peroxidise. Glutathione peroxidise protects the body from free radical damage. In this role as an antioxidant, selenium helps prevent damage to the body's tissues, cells and molecules which can lead to reduced risk of degenerative diseases such as coronary heart disease, arthritis and certain cancers.
For athletes, protection against free radicals is important for protection of tissues, shortened recovery times and protection from the extra free radical load caused by strenuous exercise. Inadequate selenium intake is related to poor immune system function.
Specifically, supplementation with selenium reduces incidences of cancer of the liver, skin, colon and mammary glands. In addition, researchers at the University of Arizona in a 2004 study published in the Journal of the National Cancer Institute concluded that people with the highest blood levels of selenium has a 34 percent lower risk of abnormal cell growth and developing new polyps in the colon and rectum.
Preventing cellular oxidation with antioxidants is another chief benefit. There is also increasing evidence that selenium plays a role in inhibiting many aging processes and the development of chronic diseases associated with aging. Among these are arthritis, emphysema, cirrhosis of the liver and arteriosclerosis.