Leucine is one of the essential amino acids. It forms an important component of numerous proteins.
What is leucine?
Leucine (Leu) is one of a total of 21 proteinogenic essential amino acids. It also goes by the names L-leucine or leucine. Leucine is found in some foods and is considered important for muscle. L-leucine represents an alipathic amino acid and bears the chemical name alpha-aminoisocaproic acid. The characteristic features of the amino acid include a branched hydrocarbon chain. Since humans are not capable of synthesizing leucine, regular intake of the amino acid through food is required. The elimination of leucine from the body takes place through fat metabolism. In part, its excretion also occurs through urine and sweat. Together with the amino acids valine and isoleucine, leucine is a component of the Branched Chain Amino Acids (BCAA). Of these three amino acids, leucine has been the best studied to date.
Function, effects, and roles
The amino acid leucine is important for protein synthesis in the human body. This means that it has a share in the building of protein in the liver and muscles. In addition, a sufficient supply of leucine is required to maintain a certain muscle mass in the body. In addition, the amino acid protects the liver from damage caused by alcohol and has a stimulating effect on fat burning. Leucine is also important for the organism as a supplier of energy. Thus, the provided energy reserves of the amino acid counteract extensive glucose breakdown. In this way, the muscles and brain are able to obtain sufficient glucose if necessary. Leucine also stimulates the release of insulin, which takes place in the pancreas. This regulates the blood sugar level in the organism. In addition, the absorption of the amino acid through the muscle tissue is accelerated, which in turn promotes the building of muscles. At the same time, the release of the stress hormone cortisol is reduced. Leucine also has a positive effect on the growth of children and adolescents because it promotes the release of the important hormone somatotropin, which in turn has a favorable effect on organ development. In adult humans, somatotropin regulates the amount of fat and muscle. At the same time, it supports the provision of free fatty acids. L-leucine also serves as the starting building block of glutamic acid, through which it participates in several metabolic processes that are essential for life. Leucine is an important component of numerous proteins. Its hydrophobic nature is important for the formation of the secondary structure. In addition, the amino acid is also found in body fluids such as saliva, cerebrospinal fluid, plasma and milk.
Formation, occurrence, properties, and optimal values
The human body cannot produce leucine itself. Therefore, its intake must come from the diet. Another option is the intake of special dietary supplements that serve to build muscles. Leucine is found in larger quantities in cow’s milk, beef, chicken eggs, salmon, rice, walnuts, and whole wheat and corn flour. Other foods containing leucine include peas, tuna and olives. The daily requirement for the amino acid L-leucine is about 1.2 grams. Depending on which method is used, the daily requirement averages 15 milligrams per kilogram of body weight. In principle, the required amount can be covered by a balanced diet. However, if a person is exposed to strong athletic stress on the muscles, because he practices endurance or strength sports, he needs additional amounts, which can be supplied with the help of a dietary supplement.
Diseases and disorders
In some cases, a deficiency of L-leucine may occur. This is usually caused by an insufficient intake of foods containing leucine. However, a vitamin B6 deficiency is also not infrequently the reason for a leucine deficiency. The deficiency symptoms become noticeable through constant fatigue. In addition, the affected persons usually feel fatigued. In addition to an undersupply, an overdose of the amino acid is also possible. Thereby the risk exists that a disturbance of the protein formation occurs. In addition, an efficient build-up of the muscles is counteracted.As a result, those affected suffer from symptoms such as nausea, diarrhea and abdominal pain. Hyperaminoaciduria often increases the isoleucine level within the blood tenfold. Furthermore, degradation substances such as isovaleric acid appear in the blood plasma. If transport or resorption impairments of leucine occur, this not infrequently leads to Hartnup syndrome, which is associated with severe symptoms. Those affected suffer from eczema, diarrhea, depression, headaches, paresis and aminoaciduria. If L-leucine is degraded due to a deficiency of the enzyme alpha-keto acid decarboxylase, babies may develop maple syrup disease, a metabolic disorder. Already in the first week of life of the affected child, symptoms such as vomiting, seizures, a sweet-spicy smell of the urine, lethargy and weakness in drinking appear. Even a coma is possible. Without appropriate therapy, the newborn is at risk of death from ketoacidosis. However, leucine also has positive effects on certain diseases. For example, the healing process of muscle tissue diseases, joint diseases and liver disorders is promoted by the amino acid. Together with glycine and other proteinogenic amino acids, leucine is also used in medical infusion solutions. Anyone taking L-leucine additionally via dietary supplements should ensure better absorption within the intestine by providing the body with sufficient fluids. In this way, a higher availability in the cells of the muscles is ensured.
