Selenium

Selenium is an important mineral antioxidant in human nutrition. Since exercise (particularly endurance exercise) is associated with an increased production of potentially damaging oxidative by-products (peroxides and free radicals) in muscle fibers, it is possible that selenium may play a role in reducing muscular oxidative stress. A selenium deficiency may result in muscle weakness and increased recovery time after exhaustive exercise. There is little evidence, however, that increasing the intake of supplemental selenium increases exercise performance. The adult male and female DRI for selenium is 55 micrograms per day. Nutritional supplements, including sodium selenite and high-selenium yeast, are effective sources of selenium, but excessive intake may be toxic, so proper care in taking appropriate supplement levels is important. The safe upper limit is set at 400 micrograms per day for adults, with brittle hair and nails a sign of toxicity.