Glutamine also strengthens the rapidly growing cells, or so-called lymphocytes, of the immune system, which help the body defend itself against what it recognizes as foreign invaders, such as microbes.    Additionally, glutamine maintains the body's acid-base balance, i.e. the maintenance of a stable internal environment in a body in terms of pH, in cases of disturbance by external factors.    In the brain, glutamine is converted to glutamic acid which is essential for brain function.