Selenium (Yeast-Free) 200 mcg Tablets contain selenium, a key mineral which can naturally be found in the soil. It is a vital mineral as it supports the immune system and protects the cells from oxidative stress caused by free radicals. Free radicals are unstable molecules that can damage the cells in your body and are associated with premature aging. This mineral can be naturally found in Brazil nuts, eggs, fish and poultry. Making sure your levels of Selenium are adequate will help keep hair and nails healthy, as well as support your metabolism.