Glutamine is the most abundant free amino acid within the human muscle and blood. It is a building block for protein and involved in many vital functions. Glutamine is required for rapidly dividing cells, including those of the gut, and is a precursor of the brain neurotransmitter glutamate.
Glutamine also acts as a fuel for some tissues as well as for components of the immune system such as lymphocytes and macrophages.
Certain factors such as heavy exercising can lower the glutamine levels in the body. Glutamine supplements cause a rapid rise in cellular glutamine levels and glutamine stores in muscle.