Branched-chain Amino Acid

A branched-chain amino acid (BCAA) is an amino acid having aliphatic side-chains with a branch (a carbon atom bound to more than two other carbon atoms). Among the proteinogenic amino acids, there are three BCAAs: leucine, isoleucine and valine.

The BCAAs are among the nine essential amino acids for humans, accounting for 35% of the essential amino acids in muscle proteins and 40% of the preformed amino acids required by mammals. BCAAs have been used clinically to aid in the recovery of burn victims. They are also used in the treatment in some cases of hepatic encephalopathy.

A recent study suggested that the reduction in blood BCAAs may be associated with improvement in blood sugar regulation. The mechanism remains unknown.

Another recent study suggests genetic mutations in some autism models lead to altered branched chain amino acid pathways that might be normalized with dietary supplementation.

Cota et al (1) demonstrated in 2006 that BCAAs, particularly leucine, also affect the mTOR pathway, signaling two regions of the brain. These signals decrease food intake and increase basic metabolic rate. These results led to a clinical trial by Ordman (3) to develop a nutraceutical method for controlling weight gain in humans. The potential of nutrients to signal changes in metabolism is exemplified by how BCAAs may increase muscle repair, but it is important to be aware how it may also decrease appetite.