Selenium is a trace element that is found in all the cells of the body. An adult contains around 10-15 mg of selenium with the largest concentrations being found in the liver, kidneys, thyroid gland, sexual gland (gonads), and semen. Selenium supports over 30 different selenoproteins that have a number of different functions. Among these are five glutathione peroxidases (GSH-Px) that function as antioxidants, and three deiodinases that regulate the metabolism. Of all minerals, selenium is the one that holds the greatest antioxidant potential. It works in close collaboration with vitamin E to prevent oxidative damage to cell membranes, lipids, and DNA. Selenium and sulfur bear great chemical resemblances, but sulfur is not an antioxidant and has other functions in the body.