Health Hazards

Excess selenium may increase risk of diabetes

Findings in animal studies suggest that selenium supplementation improves glucose metabolism, deficiencies of which are thought to be related to development of type 2 diabetes in humans. Data from a large clinical study on the effects of long-term selenium supplementation was analyzed to determine if there was any effect on the incidence of development of type 2 diabetes.

The study population consisted of 1202 people who lived in areas of low selenium consumption in the eastern U.S. and who did not have diabetes at the start of the study. Participants in the study were provided selenium supplements (200 micrograms per day) or a placebo and observed for an average of 7.7 years. Type 2 diabetes developed in 58 selenium recipients and 39 placebo recipients, a statistically significant difference at the 95% confidence level. The lack of benefit of selenium supplementation was observed regardless of age, sex, body mass index or smoking status of the participants. Participants who had the highest levels of selenium in their blood (top third selenium blood levels) were at the greatest risk of developing type 2 diabetes, with an increased risk of 2.7 fold compared with participants with the lowest selenium levels.

The study concludes that “selenium supplementation does not seem to prevent type 2 diabetes and may increase risk for the disease.”

Link to abstract of study in Annals of Internal Medicine