Why we love it? One Nutrition L-Glutamine is a highly purified source of the most common amino acid in your body: glutamine. Amino acids form the proteins that help build muscles. But during intense exercise, your glutamine levels fall, your stamina reduces and recovery time takes longer. Your body's craving for glutamine is far greater than supply because it can't generate enough. ... and why you will too Many people take it as part of their sports nutrition programme or to help with their gut function, improve concentration, cope better with stress or to simply support their immune system.