Selenium supplementation may raise the risk for type 2 diabetes, reports a study published early online in the Annals of Internal Medicine.

In an analysis from the Nutritional Cancer Prevention study, researchers sought to determine whether selenium supplementation would lower the risk for type 2 diabetes. Some 1200 adults were randomized to receive 200 micrograms of the supplement or placebo daily. Nearly all participants were white.

During a mean follow-up of about 8 years, diabetes developed in more people taking selenium than in those on placebo. The difference was largely confined to participants in the highest tertile of baseline plasma selenium; in that subgroup, selenium recipients had 2.4 times the diabetes risk as placebo recipients.

Editorialists conclude that "people with diets that provide the Recommended Dietary Allowance for selenium (55 micrograms/day) should avoid selenium supplements, except in the context of experimental studies."