Natural Factors Selenium - 100 mcg - 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 Selenium is a mineral supplement providing antioxidant protection for the maintenance of healthy body cells and good health.