Most Americans Don’t Need Extra Selenium
Review Finds Evidence That Selenium Supplements May Increase the Risk of Type 2 Diabetes
Selenium Supplements: Too Much of a Good Thing? continued...
The review found that for people who have low selenium levels, taking supplements sometimes helps.
One study of adults in the U.K. who had low selenium levels, which are more common in Europe, found that people who took supplements were able to fight off a virus more quickly than those who took a placebo.
And supplements boosted sperm quality in men with fertility problems who also had low selenium intakes, allowing 11% to father a child. The men who took a placebo fathered no children. Selenium supplements have also shown promise for thyroid problems, though researchers say those results are early and need to be confirmed.
Studies in the U.S. that have tested supplements for cancer and heart disease protection have found no evidence of benefit, and indeed, in people who had the highest selenium levels going into the studies, taking supplements was tied to increased risks of harm.
Selenium and Diabetes
One study of more than 1,200 Americans, for example, found that those who took 200 micrograms of selenium daily for an average of nearly eight years had a higher risk of developing type 2 diabetes compared to those taking a placebo.
And those who started the study with the highest selenium levels -- 122 micrograms or higher -- saw a nearly three-fold jump in diabetes risk compared to those taking a placebo.
One limitation of that study, however, was that doctors didn’t set out to study type 2 diabetes as an outcome. People were recruited to see if selenium could cut their risk for non-melanoma skin cancer.
Researchers concede that looking at outcomes that weren’t part of the design of the study can muddy the results.
Still, other studies have also suggested an association between selenium and diabetes.
Having a higher selenium level was linked to an increased prevalence of diabetes in adults tracked by the CDC’s National Health and Nutrition Examination Surveys.
In the same vein, a French study found that higher selenium levels were associated with having higher blood sugar levels.
Researchers note that selenium might have an effect on type 2 diabetes because at high levels, it can interfere with the body’s ability to effectively use insulin.
When it comes to taking selenium, “It’s horses for courses,” says Rayman, using a British expression that means what’s suitable for one person or situation might not be suitable for another.
“There wouldn’t be a risk for us, in our population, if we took an extra 200 micrograms of selenium, but if you did that in North America, or in the U.S., then yes, you might well be putting yourself at risk,” she says.