Leucine (Leu: L) an essential amino acid and makes up approximately eight percent of the body’s protein structures. One of the three branched-chain amino acids (BCAAs), leucine is involved in muscle repair and growth together with l-isoleucine and l-valine. This amino acid helps to sustain nitrogen balance and energy supplyduring times of stress. Leucine also promotes the healing of bones, skin, and muscle tissue after traumatic injury, and is often recommended for those recovering from surgery.