Selenium (Se) is a trace mineral found in soil and water. It is also found in certain foods. Brazil nuts are the best source of selenium, while yeast, whole grains and seafood are also good sources. Selenium promotes antioxidant activity in the body via glutathione peroxidase (GPX), a selenium dependent enzyme.

As an antioxidant, selenium helps guard cells against free radical damage within the body, and as such supports healthy vision, lungs and other organs that may be subject to oxidative stress. Selenium also contributes to healthy functioning of both the immune system and the thyroid gland. In addition, selenium may promote breast health in women and prostate health in men. 

Gastrointestinal disorders may decrease the absorption of selenium, resulting in deficiency or depletion. Selenium may also be destroyed when foods are overcooked, over-processed or over-refined.