Avoid supplements in those with sufficient selenium status
A review of the evidence on the benefits of selenium supplements has identified a U-shaped curve, where people whose blood plasma selenium is already 122μg/L or higher may face harm from supplements. The average level in American men is 134μg/L.
Selenium status varies widely worldwide, with high intake associated with protection against cancer and enhanced male fertility while low status has been linked to poor immune function, cognitive decline and increased mortality, the authors said.
Too much selenium may contribute to insulin resistance.
Lancet 2012, online 29 Feb