Outcomes: Selenium Supplements May Raise Diabetes Risk

By NICHOLAS BAKALAR
Findings from animal studies have suggested that the antioxidant selenium improves glucose metabolism, so researchers decided to see whether it would reduce the incidence of Type 2 diabetes. They found that on the contrary, selenium might actually increase the risk.
The researchers used data from 1,250 people with an average age of 63, originally recruited to test selenium as a cancer preventive. The study was randomized, double-blind and placebo-controlled, which is generally considered the most reliable design. Half the people took a 200-microgram dose of selenium daily, and the other half an identical-looking dummy pill. They were followed for an average of 7.7 years. Fifty-eight selenium recipients and 39 of those who took the placebo developed Type 2 diabetes.
The study, published online yesterday, will appear in the Aug. 21 print issue of The Annals of Internal Medicine. (The findings on cancer, which were published in 1996 and 2002, were at best mixed.)
Over all, people who took selenium supplements had more than one and a half times as much risk for Type 2 diabetes as those who did not, and the higher the blood level of selenium, the greater the risk of developing the illness. The findings held even after controlling for age, sex, body mass index and smoking status.
“There is no need for Americans to take selenium supplements,” said Dr. Saverio Stranges, the lead author and an associate professor of cardiovascular epidemiology at Warwick Medical School in England. “There is already enough selenium in the average American diet.” Still, he said, “this is a single study, and no single study gives the final answer.”