Selenium

About Selenium

Selenium is an essential trace element incorporated into proteins as selenocysteine, the 21st amino acid, forming selenoproteins such as the glutathione peroxidases, the thioredoxin reductases and the deiodinases that activate and inactivate thyroid hormones. About 25 human selenoprotein genes have been identified. Official recommended intakes vary by age and life stage. The selenium content of foods depends heavily on the soil where they were grown, and in selenium poor regions of China deficiency was linked to Keshan disease, an endemic cardiomyopathy, and Kashin Beck disease, a bone and joint disorder. The SELECT trial found that selenium supplements did not prevent prostate cancer, and some studies have raised concern about a possible link between high selenium status and type 2 diabetes. Supplementation in people who already have adequate selenium has shown no clear benefit. Brazil nuts are an exceptionally rich and variable source, and an upper intake level has been set because excess causes selenosis, with hair loss, brittle nails, garlic breath and neurological symptoms.