Selenium is a trace mineral that is essential for optimal health. It is fundamental for antioxidant defence, fertility, thyroid hormone metabolism, immune response, and muscle development.
A 2002 study found that after 9 months of taking a 200 mcg selenium supplement that it had increased blood glutathione by 19 percent. Another study published in in JAMA in 1996 involving 1,300 patients, with a mean age of 63 years. All had a history of basal and/or squamous cell carcinoma. The NPC Trial showed selenium supplementation significantly decreased the total cancer incidence by 50 percent, and specifically dropped the incidence of lung cancer by 48 percent, prostate cancer by 63 percent, and colorectal cancer by 58 percent