Need
Glutamine has been traditionally classified as a nonessential amino acid. This classification means that the body is able to synthesize sufficient levels of glutamine for use in all of its important functions under normal circumstances.
However, research has shown that during periods of stress (whether from diarrheal or other illness, malnutrition, medical treatment, exercise, or aging) the rate of glutamine production and its release from skeletal muscle do not appear to compensate fully for the decline in plasma glutamine concentration resulting from such stress. More importantly, the need for glutamine appears to increase as the severity of the injury increases.
These observations suggest that a glutamine-depleted state may occur frequently due to a variety of common (aging, malnutrition or diarrhea) and uncommon (chemotherapy) events. A reduced glutamine level significantly impacts the body’s ability to:
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absorb nutrients (through decreased intestinal mucosal cellularity and function)
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fight infection (through reduced immune responsiveness)
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maintain muscle mass (through muscle wasting due to glutamine release by skeletal muscle).
Consequently, glutamine’s traditional classification as a nonessential amino acid is not completely accurate. Rather, glutamine is more properly classified as a conditionally essential amino acid reflecting the fact that in the circumstances where it is most needed (during any incidence of physical stress), glutamine must be supplemented.