Leucine is an essential amino acid that cannot be manufactured in the body, and is part of the three branched-chain amino acid family, which constitutes approximately 70% of the amino acids in the body. Leucine was named from the Greek word leukos (meaning ‘white’), because at that time, the purification of a subtance from nature to a white crystalline state was considered quite spectacular. The stucture of leucine was established by laboratory synthesis in 1891.
Leucine assists the regulation of blood-sugar levels, the growth and repair of muscle tissue, growth hormone production, energy regulation and wound healing. During times of starvation, infection, or recovery from trauma and stress, the body mobilises leucine as a source for gluconeogenesis (the synthesis of blood sugar in the liver) to aid in the healing process. It has also been suggested that leucine may have beneficial therapeutic effects on the prevention of protein wasting, as it occurs during trauma, or recovery after surgery etc.
Young adults need about 31mg of this amino acid per day per kilogram (14 mg per lb) of body weight. Therapeutic use of leucine for the average person occurs at doses between 500 and 1,000mg per day. Deficiency is rare, since it can be found in all protein foods, but vegans and vegetarians without adequate protein sources are more prone to deficiency. Insulin deficiency is known to result in poor utilisation of leucine; therefore, individuals who suffer from glucose intolerance may require higher levels of leucine. Hypoglycemia symptoms appear if the diet is deficient, which may include dizziness, fatigue, headaches and irritability.
Leucine is thought to be beneficial for individuals with phenylketonuria - a condition in which the body cannot metabolise the amino acid phenylalanine. In conjunction with the other branched chain amino acids (BCAA’s), isoleucine and valine, it also appears to be quite helpful in treating, and in some cases even reversing, hepatic encephalopathy, a form of liver damage in alcoholics, and helps prevent muscle wastage associated with this disease. These BCAA’s also lessen the adverse neurological effects of chronic liver disease.
Supplements and protein powders that contain leucine are used extensively by bodybuilders and other athletes to promote muscle recovery. It is one of the most important amino acids for hard-training body builders, as leucine, along with isoleucine and valine, escape liver metabolism and can directly and significantly influence muscle-protein metabolism. Leucine appears to be the most important BCAA for athletes, as it can affect various anabolic hormones and has an effect on preventing protein degradation.