Selenium Supplements: Diabetes Risk?
Study: Taking Selenium Supplements May Raise Type 2 Diabetes Risk
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
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
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
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
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
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.
Selenium Study's Results
During the study, 58 participants in the selenium group reported being
diagnosed with type 2 diabetes, compared with 39 people taking the
The possible link between type 2 diabetes and selenium supplementation held
when the researchers considered participants' age, sex, BMI (body mass index,
which relates height to weight), and smoking habits.
But the study had a pretty narrow group of participants -- older adults with
a history of nonmelanoma skin cancer -- and wasn't designed with diabetes in
mind. So further studies are needed to see if selenium supplements truly raise
diabetes risk, note the researchers.
Selenium Study Editorial
Stranges' study is accompanied by an editorial by doctors including Joachim
Bleys, MD, MPH, of Johns Hopkins University Bloomberg School of Public
The editorialists note that obesity and lack of physical activity are the
main causes of diabetes. They also point out that most people in the U.S. get
enough selenium from their diet.
"By taking selenium supplements on top of an adequate dietary intake,
people may increase their risk for diabetes," write Bleys and
That's just a theory at this point, but that theory "may be biologically
plausible," write the editorialists.