The branched-chain amino acids (BCAAs) comprise the three essential amino acids L-leucine, L-isoleucine and L-valine. These amino acids are found in proteins of all life forms. Dietary sources of the branched-chain amino acids are principally derived from animal and vegetable proteins. Vegetables and juices contain small amounts of the free amino acids, which are also found in fermented foods like yogurt and miso. Several years ago the branched-chain amino acids created some interest in the neurological research community when a pilot study indicated that amyotrophic lateral sclerosis (ALS) patients showed symptomatic improvement when given large doses of BCAAs. It was theorized that BCAAs may protect against neuronal damage from the neuroexcitatory neurotransmitter glutamate. Based on this pilot study, branched-chain amino acids received orphan drug approval for the treatment of ALS. Unfortunately, most of the followup studies were negative, and one even suggested that BCAAs may increase mortality in those with ALS. Branched-chain amino acids are sometimes used in enteral and parenteral feedings in the management of hepatic encephalopathy. They are also occasionally used enterally and parenterally in the management of extensive burns and other severe trauma conditions because of their possible anticatabolic action in these conditions. L-leucine is also known as 2-amino-4-methylvaleric acid, alpha-aminoisocaproic acid and (S)-2-amino-4-methylpentanoic acid. It is abbreviated as Leu or by its one letter abbreviation L. Its molecular formula is C6H13NO2, and its molecular weight is 131.17 daltons