"Most people believe that both selenium and the selenium-containing enzyme GP are good for health by protecting cells and tissues from oxidation. However, this study suggests that they are a double-edged sword," says Lei. "Antioxidants can be harmful by neutralizing too many free radicals and interfering with insulin signaling, which results in promoting obesity, insulin resistance and possibly diabetes."

He points out that these findings are consistent with a recent study of pregnant women that reported on a link between high levels of GP, insulin resistance and gestational diabetes.

"Before people blindly supplement their diets with antioxidants, such as selenium and vitamins E and C, more research is needed," he concludes. Next, Lei plans to put the obese mice from this study on a diet to see if weight loss and fat loss can prevent or improve the mice's insulin sensitivity.

Other authors of the study are Donald Lisk, a toxicologist and Cornell professor emeritus of horticulture, research support specialist Carol Roneker, Cornell graduate student Weipeng Mu and Paul Langlais and Feng Liu of the University of Texas Health Science Center-San Antonio . McClung presented the research to the Experimental Biology 2004 meeting in Washington, D.C., in April and received first prize from the American Society of Nutritional sciences in a graduate student competition award.

The study was funded in part by the National Institutes of Health.

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