Glutamine an amino acid of central importance

Glutamine is present in peptide bonds in the protein in the food but it is also present in the free form in meat and some root vegetables. It is released by proteolysis in the small intestine and absorbed into the enterocytes. Here some of it is metabolised so that only about 50% or less of the absorbed glutamine enters the blood. However, if the food is supplemented with glutamine or if it is ingested as a bolus, a significant proportion enters the blood. To maintain the physiological blood level under normal conditions, it must be synthesised de novo in the body. 

Fuel for immune cells at rest and during proliferation. Enhances T-lymphocyte responses to infection. 

Fuel for enterocytes and for stem cells in the crypts of villi. Maintenance of gut-associated lymphoid tissue (GALT). Maintenance of gut barrier, especially that in the colon. 

Fuel for endothelial cells (largest number of endothelial cells 

The three tissues that fulfil this role are skeletal muscle, adipose tissue and lung. Of these, muscle is quantitatively the most important. 

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