Lysine is an essential amino acid, meaning that the body cannot produce it on its own and must obtain it from food. It plays a crucial role in protein synthesis, hormone production, and the absorption of calcium. Foods rich in lysine include meat, fish, dairy products, beans, and legumes. In addition to its importance in nutrition, lysine is also known for its potential health benefits. It may help in reducing the severity and duration of cold sores caused by the herpes simplex virus. Some studies suggest that lysine supplements can support immune function and improve overall health.