Contrary to expectations, high blood levels of selenium are linked with diabetes in adults. Previous animal studies have suggested that oxidative stress reduces insulin secretion and increases insulin resistance. Therefore, it had been hypothesised that because selenium has antioxidant properties, high levels of selenium in the body may prevent diabetes. Selenium is a mineral required in small amounts to maintain good health. It is necessary to generate antioxidant proteins that help prevent cell damage from free radicals, which are thought to contribute to the development of chronic diseases. Selenium also has a role in regulating thyroid gland function and the immune system. Researchers from the Johns Hopkins University Bloomberg School of Public Health, Baltimore, USA, analysed data from 8,876 subjects, at least 20 years of age. The investigators defined diabetes as a fasting blood sugar level of at least 126 milligrams per decilitre; patient reports of a physician's diagnosis of diabetes; or the current use of insulin or an oral diabetes medication. The results of the study ran counter to what was anticipated. After accounting for the potential effects of age, sex, race, and weight, the researchers found that blood levels of selenium were 127 nanograms per ml in diabetics and 125 nanograms per ml in subjects without diabetes, a minor but statistically significant difference. Upon further analysis, the researchers found that subjects with the highest levels of selenium were 57 percent more likely to have diabetes than those with the lowest levels. The researchers call for more research to investigate high blood levels of selenium as a factor that can increase the risk of diabetes. Until the findings of additional studies are available, increased levels of selenium, through the diet or in supplements, are not recommended for diabetes prevention in individuals with normal selenium levels.
Diabetes Care,
April 2007