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Selenium Supplements: Diabetes Risk?

Study: Taking Selenium Supplements May Raise Type 2 Diabetes Risk
WebMD Health News
Reviewed by Louise Chang, MD

July 9, 2007 -- Taking selenium supplements may, over time, make type 2 diabetes more likely, a new study shows.

The study, published in the Annals of Internal Medicine's advance online edition, doesn't prove that selenium supplements cause type 2 diabetes.

But the researchers write that selenium supplements don't appear to prevent type 2 diabetes and "may increase risk for the disease."

Selenium is a mineral found in the soil and in plants.

The body needs small amounts of selenium. Too much selenium can cause health problems including stomach upset, hair loss, nail problems, and nerve damage.

The new study comes from researchers including Saverio Stranges, MD, PhD, who worked on the study while at the State University of New York at Buffalo. Stranges now works at Warwick Medical School in the U.K.

Selenium and Type 2 Diabetes

Stranges' team studied data on some 1,200 U.S. adults enrolled in a cancer prevention study.

The participants were 63 years old, on average. They lived in areas where the soil had low levels of selenium.

All participants had previously had nonmelanoma skin cancer. But none reported having type 2 diabetes when the study started.

The study mainly focused on selenium and cancer. The researchers also tracked new cases of type 2 diabetes, since experiments on animals had suggested that selenium supplements might help prevent type 2 diabetes.

Selenium Supplement Study

The researchers randomly split participants into two groups.

One group was assigned to take selenium supplements in a daily dose of 200 micrograms.

That’s higher than the Institute of Medicine's recommended dietary intake of 55 micrograms per day of selenium for men and for women who aren't pregnant or breastfeeding. But it's lower than the Institute of Medicine's upper limit of 400 micrograms of selenium per day.

For comparison, the other group took placebo pills containing no selenium. Participants didn’t know whether they were taking the selenium supplements or the placebo.

Participants were followed for nearly eight years, on average. During that time, they reported any new diabetes diagnoses and got their blood levels of selenium checked twice yearly.

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