Quest Synergistic Selenium 200μg Combines selenium with vitamins C and E to create a potent antioxidant formula. Selenium, vitamin C and vitamin E help protect body cells from oxidative stress. Selenium also supports the normal function of the immune system and contributes to the normal production of sperm to support male fertility. It plays a role in normal thyroid function and is involved in the maintenance of hair and nails. Its antioxidant action may exert a protective effect, low levels of selenium may increase the risk of developing autoimmune disorders such as rheumatoid arthritis, cardiovascular disease and some cancers.