Amino acids (AAs) are important biological compounds that serve as the building blocks for all proteins. Of the 20 standard AAs, three contain branched side chains, or a non-continuous link of carbon bonds: leucine, isoleucine and valine. These branched chain amino acids (BCAAs) are among the nine essential amino acids for humans meaning they cannot be made by the body and must be consumed through the diet. They account for ~35% of the amino acids found in skeletal muscle and make up 40% of the daily requirements for essential amino acids.
Whereas most amino acids are broken down and converted to energy in the liver, BCAAs are uniquely metabolised in skeletal muscle. Once ingested, BCAAs enter the blood stream and are directly absorbed into skeletal muscle where they can be used for energy, muscle repair and building and/or conversion into alanine or glutamine which can be shuttled to the liver for the formation of new blood glucose. BCAAs can also cross the blood brain barrier where they are involved in the maintenance of glutamate and gamma-aminobutyric acid (GABA), an important neurotransmitter in nervous system function.