Bloomberg News reports, “Supplements of selenium, a trace mineral that may help prevent some cancers, might increase the risk of type 2 diabetes if taken in large quantities, according to a review of existing studies” published in The Lancet.
After examining “studies published between January 1990 and February 2011,” Professor Margaret Rayman, of the UK’s University of Surrey, said that “to help prevent raising the chance of developing diabetes, people with selenium levels of 122 micrograms per liter or higher in their blood shouldn’t take selenium supplements.”
In addition, “higher-than-normal levels of selenium may contribute to the development of…hair loss and certain cancers,” HealthDay reports.
“The average daily intake recommendations for selenium are 60 micrograms per day for men and 53 micrograms per day for women, according to the research.”
The study found, however, that “daily intake of selenium varied from as little as 7 micrograms per day to as much as 4,990 micrograms per day. In Europe, the average intake was 40 micrograms per day, and in the United States, the average daily intake was 93 micrograms for women and 134 micrograms for men. Selenium supplements are likely part of this intake,” investigators reported.
WebMD points out, “The US Institute of Medicine has set a tolerable upper limit for selenium at 400 micrograms a day. Too much selenium can cause a condition called selenosis, which includes symptoms, such as gastrointestinal upset … white blotchy nails, garlic breath odor, fatigue, irritability, and mild nerve damage.”