Selenium supplements may raise type 2 diabetes risk
Last Updated Sep 2007
Last Updated: 2007-07-09 17:00:31 -0400 (Reuters Health) NEW YORK (Reuters Health) - In the largest and longest clinical trial to date comparing the effects of selenium supplements versus placebo or dummy pills, daily doses of the mineral failed to reduce the occurrence of type 2 diabetes and may have increased it. In the study, people who took a 200 microgram selenium supplement each day for almost eight years had an increased risk of developing type 2 diabetes relative to people who took a placebo. "At this time, the evidence that people should take selenium supplements is extremely limited," study chief Dr. Saverio Stranges, from the Warwick Medical School in Coventry, UK, said in a statement. "We have observed an increased risk for diabetes over the long term in the group of participants who took selenium supplements." Selenium is a naturally occurring trace mineral present in soil and foods. The body requires minute amounts of selenium to aid in metabolism. Because of its anti- oxidant properties, selenium was believed to improve the body's ability to metabolize sugar and protect against diabetes, Stranges and colleagues explain in an early release article in the Annals of Internal Medicine, scheduled for print publication in the August 21st issue. However, evidence for such a benefit is inconclusive. The new data come from the Nutritional Prevention of Cancer Trial (NPC), a large study designed to evaluate whether selenium supplements prevent skin cancer. A "secondary" study outcome was the onset of diabetes. Results showed that 58 out of 600 people assigned to receive selenium (200 micrograms daily) and 39 out of 602 allocated to the placebo group developed type 2 diabetes. After 7.7 years of follow-up, the risk of diabetes was roughly 50 percent higher among those assigned to selenium than among those assigned to placebo. The detrimental effect remained higher in the selenium group in analyses stratified by age, gender, body weight, and smoking status. "No single study," Stranges noted, "can provide the answer to a scientific question, but at this time, selenium supplementation does not appear to prevent type 2 diabetes, and it may increase risk of the disease. However, our understanding of the mechanisms whereby selenium would increase risk of diabetes is very limited at this time and this issue needs to be further explored. Nevertheless, I would not advise patients to take selenium supplements greater than those in multiple vitamins." The authors of a commentary on the study say the public health implications of these findings are "substantial," noting that more than 1 percent of the US population takes selenium supplements and more than 35 percent take multi-vitamins that often contain selenium. Dr. Eliseo Guallar from Johns Hopkins University Bloomberg School of Public Health in Baltimore and associates also point out that selenium has a narrow therapeutic range, and 99 percent of people in the US have dietary intakes of selenium that surpass the Recommended Dietary Allowance. So until high-quality studies establish that the benefits outweigh any risks, they advise that selenium supplements should be avoided. SOURCE: Annals of Internal Medicine 2007.
Dr. Sears Comment
Just another study that indicates micronutrients have microbenefits. It is only when you change the macronutrient content of the diet that significant benefits in diabetics can occur.