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This article is an extract from my book Griffiths' Sport Supplement Review and is protected by copyright. Permission is given to copy this article on other websites as long as this statement is included with a link back to this site.


Other names

(2S)-2,5-diamino-5-oxopentanoic acid
2-Amino-4-carbamoylbutanoic acid
2-aminoglutaramic acid
glutamic acid 5-amide
What is it?

A non essential amino acid which is the most abundant amino acid in the human body. It is produced from glutamate and ammonia by many body tissues including muscles, kidney, heart, liver and lungs.
Claimed benefits

Improves recovery from intense exercise.
Anabolic action.
Prevents post exercise immune system suppression and protects against minor infections.
Mode of Action

Improved recovery via increased post-exercise glycogen re-synthesis and increased protein synthesis.
Anabolic action via increased protein synthesis.
Immune system support by preventing post exercise falls in glutamine levels which is used for energy by immune system cells.

The first question to answer regarding glutamine supplementation is whether it can be effectively absorbed in an oral form. There is a trend in sport supplements to promote protein bound or peptide bonded forms of glutamine which are claimed to have a much higher bioavailability than simple free form L-glutamine.
It is true that most L-glutamine consumed orally never makes it to the blood stream since it is used by the intestines for energy. In fact approximately 65% of orally consumed glutamine is used by the intestines in this way (1). However
this means that 35% is absorbed and in fact blood levels of glutamine rise in an almost linear dose dependent fashion as more glutamine is consumed (2).
Secondly several studies have demonstrated that protein or peptide bonded forms of glutamine are either absorbed no better than free form L-glutamine (3) or are in fact absorbed worse (4). Therefore if one chose to supplement with glutamine the free form L-glutamine type would be the sensible choice.
Now we will address the question of whether increasing blood levels of glutamine can increase muscle protein synthesis.
Several in vitro studies conducted on animal cells have shown that increasing intramuscular concentrations of glutamine have an anabolic effect by preventing protein
breakdown and increasing protein synthesis (5) (6) (7).
In humans the picture is not quite as clear. Most of the studies involving glutamine supplementation in humans have involved acutely unwell patients in catabolic states suffering from trauma, burns or post-surgery. In these groups of people glutamine supplementation has been shown to be beneficial in improving outcomes and in particular in helping to enhance net protein synthesis in skeletal muscle (8) (9).
However in these groups of people glutamine supplementation should be viewed as correction of a glutamine deficiency rather than true supplementation since after severe stress glutamine is mobilized from the muscle to provide energy and hence muscle levels are reduced. Under these circumstances glutamine becomes a conditionally essential amino acid since the body uses
more than it can produce.
Since this is not the case with healthy individuals these studies are not really helpful in assessing the benefit of glutamine to healthy athletes. Those few studies which have been conducted on healthy individuals are equivocal.