Leucine is an essential amino acid, and it cannot be synthesized by the human body. It is one of the three branch-chained amino acids. It makes up one of the components of the collective term protein. The human body is roughly 16 percent protein. Protein plays an essential role in every cell of our body.
There are 20 amino acids used by the human body and 8 of them cannot be synthesized. Leucine is one of those that must be acquired by diet. Leucine is manufactured by plants and microorganisms.