Like its cousin isoleucine, leucine is one of the most common amino acids known in human anatomy and physiology. In fact, leucine is only second to glycine in terms of amino acid concentrations found in proteins. L-leucine’s chemical composition is identical to that of isoleucine, but yields dissimilar properties due to the different arrangement of atoms. In humans, leucine remains nutritionally essential. This nutrient is incapable being synthesized in mammalian tissues.

Leucine continues to work in sync with the amino acids isoleucine and valine, to protect muscle and act as fuel. These three critical amino acids (isoleucine, leucine, and valine) form the branched-chain amino acids; paramount in promoting “the healing of bones, skin, and muscular tissue.” [1]