Glutamine is used in the gut and immune system to maintain optimal performance. 60% of free-form amino acids floating in skeletal muscles is L-Glutamine. After an intense training session, glutamine levels in the body are almost halved.
L-Glutamine plays a very important role in protein metabolism, thus is an important nutrient for bodybuilders. Glutamine can help reduce the amount of muscle deterioration that occurs as other tissues that need glutamine will not rob the glutamine stored in the muscle cells.
In summary, glutamine promotes nutrient assimilation, regulates protein synthesis, stimulates growth-hormone production and enhances the immune system. As bodybuilders use a lot of their glutamine when training, the immune system relies heavily on this amino acid. Glutamine supplementation keeps muscles building, not being robbed of glutamine for use elsewhere such as nitrogen transport or maintaining the immune system.