Selenium-containing amino acids are specialized amino acids that incorporate the element selenium into their structure. The most notable examples are selenocysteine and selenomethionine. These amino acids play crucial roles in various biological processes, including antioxidant defense and thyroid hormone metabolism. Selenium is an essential trace element for humans, and its incorporation into amino acids allows for the synthesis of important proteins, such as glutathione peroxidase. These proteins help protect cells from oxidative damage and support overall health. Adequate dietary intake of selenium is important for maintaining optimal levels of these amino acids.