There is some new research showing that selenium might increase the risk of someone contracting diabetes. Selenium is often used as an antioxidant to boost immunity and prevent cancer. Evidence indicate that taking 200 mcg/day for about 7 years raises the risk of type 2 Diabetes by about 50% compared to placebo. This comes to an increase of about 4 cases per 1000 patient years.
The current upper limit of selenium is 400mcg/day. Some “experts” will recommend lowering it to 200mcg/day.