At present, the main components of selenium-supplemented health products on the market are inorganic selenium (sodium selenite), organic selenium (selenium yeast) and nano-selenium. The "Selenium King Capsule" produced by Shanghai Sitong Nanotechnology Port Co., Ltd. is the only "nano selenium" product approved by the Ministry of Health, and its biological activity is 5-7 times higher than that of traditional inorganic selenium (sodium selenite) and organic selenium (selenium yeast). At the same time, it is less toxic than inorganic selenium and organic selenium, and is known as the "noble in selenium", which is the safest and most reassuring in the market at present.