Have we enough glutamine and how does it work? A clinician's view.

There is a gap between the scientific basis of the claim that in several disease states glutamine is lacking and the widespread belief that supplementation of glutamine to the nutritional regimen is beneficial in severely ill patients. Glutamine shortage exists when consuming tissues, playing a crucial role in the response to trauma and disease, receive insufficient amounts of glutamine. In these tissues (immune system, wound), glutamine is only partly oxidized but has more specific roles as nontoxic nitrogen carrier, precursor of several crucial metabolites required for cell proliferation and for maintenance of the redox potential, and as osmolyte. In inflammatory states, glutamine concentrations in plasma and tissues are decreased due to many disease-related factors, precluding its use as a reliable indicator of shortage. Isotope studies have yielded equivocal results, precluding their use as a reliable indicator of glutamine shortage or adequacy. The increase in the net release of glutamine from peripheral tissues to central tissues (immune system, liver, spleen, wound) in inflammatory states provides a better basis for the necessity to supplement the organism with extra glutamine in these conditions. Glutamine supplementation was beneficial in a few studies in burn or trauma patients. The clinical benefit of parenteral glutamine supplementation in patients with severe inflammation has been demonstrated more convincingly. The amounts of glutamine supplemented approximate the amounts released by peripheral tissues and utilized by central organs operative in host defense and are therefore in the physiological range.