Selenium(Se)was discovered by Swedish chemist Jacob Berzelius(1779-1848)on 1817 and has become one of the most influential natural-occurring trace elements for humans,animals,and even plaints.Till now,it is recognized that two Se-containing amino acids-selenomethionine(SeMet)and selenocysteine(SeCys)are involved in the regulation of two important enzymes families-glutathione peroxidases and thioredoxin reductases.These enzymes play important roles in human physiology,especially in protection from oxidative damage and regulation of intracellular redox state and thyroid hormone metabolism.However,low Selenium (Se) was discovered by Swedish chemist Jacob Berzelius (1779-1848) on 1817 and has become one most influential natural-occurring trace elements for humans, animals, and even plaints.Till now, it is recognized that two Se- containing amino acids-selenomethionine (SeMet) and selenocysteine ​​(SeCys) are involved in the regulation of two important enzymes in families-glutathione peroxidases and thioredoxin reductases. These enzymes play important roles in human physiology, especially in protection from oxidative damage and regulation of intracellular redox state and thyroid hormone metabolism .However, low