Glutamine consists of 19% nitrogen, making it the primary transporter of nitrogen into your muscle cells. During intense training, Glutamine levels are greatly depleted in your body, which decreases strength, stamina and recovery. It could take up to 6 days for Glutamine levels to return to normal - and Glutamine plays a key role in protein synthesis. Studies have shown that L-Glutamine supplementation can minimize breakdown of muscle and improve protein metabolism.
How glutamine works in the body.
Being that glutamine is one of the more predominant amino acids in the body, it plays many important roles, some of which will have a direct impact on the results you see from your training program. The first big role, as touched upon briefly above, is that glutamine acts as a substrate for DNA synthesis. This literally means that without glutamine being present in the body, your body would not be able to manufacture many of the cells it needs on a daily basis. Glutamine is also involved in the protein synthesis process, so after each workout after you've broken down muscle tissue, it will help to rebuild this muscle back, growing stronger (and larger if you're in a calorie surplus) in the process.
Apart from these two roles, glutamine also serves as a source of fuel for enterocytes, which are cells that line the inside of the small intenstine, acting as the precursor for multiplying immune cells, as well as helps to promote a healthy immune systems. Severe burn patients are often treated with high doses of glutamine because of this fact in an attempt to boost the recovery processes taking place. Finally, glutamine also serves to be an alternate source of fuel for the brain and helps to block cortisol-induced protein catabolism, which is likely to be particularly high when you're dieting.