Q. I saw a report citing a study published in the Annals of Internal Medicine that tracked 1202 people for 8 years. It showed there was a 50 percent increase in type 2 diabetes in the people taking a supplement of 200 micrograms of selenium.
My multivitamin has 100 micrograms, so if I ate just two Brazil nuts, I’d be over the limit. How much should I worry about this?
A. The research you refer to was published on Aug. 21, 2007. It did find an increased risk of type 2 diabetes: 58 cases in the selenium-supplemented group compared to 39 cases in the placebo group during the study. The scientists had expected to find a protective effect of selenium supplementation instead of greater risk.
A smaller study did not find a link between selenium supplementation and risk of type 2 diabetes, but it lasted only six months (PLoS One, Sept. 19, 2012). In addition, it looked at an intermediate marker, the blood chemical adiponectin, instead of cases of diabetes.
There’s no evidence we know of that selenium in your diet will raise your risk of diabetes. To be on the safe side, though, we suggest limiting your Brazil nut consumption; they are quite high in selenium. You should ask your doctor to monitor your blood sugar levels periodically.
You can learn a bit more about selenium toxicity (and Brazil nuts) in this earlier People’s Pharmacy post.
