Natural Factors Seleno Excell Selenium - 200 mcg - Selenium is a vital antioxidant with properties that may slow down the aging and deterioration of tissues caused by free radical damage. It protects the immune system by preventing the formation of free radicals that can damage the body and preserves the elasticity of tissue that become less elastic with aging. Selenium also aids in fighting infections and has been shown to play a role in thyroid gland activity. Natural Factors Seleno Excell Selenium is an organically bound high selenium yeast that provides increased bioavailability for the human body. High selenium yeast has proven effective in clinical trials. It is a mineral supplement for the maintenance of healthy body cells and good health.