There are considerable amounts of research into the use of glutamine in bodybuilding and other sports, but with very mixed results.
Some scientific evidence points to glutamine being of little use in bodybuilding, but anecdotal reports and other studies have shown significant benefits. Like I siad very mixed results.
In bodybuilding it is used for the same reasons as in medicine, i.e. aiding recovery, in that weight training stresses our bodies intensely.
However if you look at it from the point of view that when demands for glutamine are high and there is insufficient dietary glutamine, the body cannot manufacture sufficient amounts, so it is taken from muscle stores.
Therefore, not only do we have insufficient amounts for muscle growth, but glutamine is also taken from muscle. Exogenous glutamine is therefore
anti-catabolic.
Also, the way in which glutamine is taken is debatable.
Many MRPs are loaded with extra glutamine, and also some quality protein powders contain added glutamine over and above the source of the protein.
Studies have shown that 50 - 85% of supplemented glutamine is not absorbed like Nite has already pointed out, this is due to other amino acids competing for intestinal absorption, so if I was to take it I would take one dose of one to two grams at least half an hour away from other protein sources.
IMO Glutamine has its place for the more advanced bodybuilder, in aiding recovery, but has no real benefit for moderate to beginners.
Surfer