Selenium supplementation enhances low selenium levels and stimulates glutathione peroxidase activity in peripheral blood and distal colon mucosa in past and present carriers of colon adenomas.

Selenoproteins such as glutathione peroxidases (GPx), thioredoxin reductases (TrxR), and selenoprotein P (SePP) contain molecular selenium in form of selenocysteines within their active center. They are involved in the defense of reactive oxygen species, which otherwise may cause DNA damage and alterations of protein function. Selenium intake has been linked to colon carcinogenesis in epidemiological and interventional studies.