Isoleucine is an essential amino acid, meaning that the body cannot produce it and must obtain it from food sources. It plays a crucial role in protein synthesis, tissue repair, and energy production. Isoleucine is particularly important for athletes and those engaged in intense physical activity, as it helps in muscle recovery and endurance. This amino acid is found in various protein-rich foods, including meat, fish, eggs, dairy products, and certain plant-based sources like legumes and nuts. Isoleucine is one of the three branched-chain amino acids (BCAAs), along with leucine and valine, which are known for their role in promoting muscle growth and reducing exercise fatigue.