The amino acid requirements of disease

It is now clear that accidental injury, surgery, infection, cancer and psyc hosocial stress activate new metabolic pathways that consume amino acids. F or example, immune activation appears to alter glutamine and arginine metab olism, acute phase protein synthesis demands the increased provision of the aromatic and sulfur amino acids, while an increased rate of glutathione tu rnover increases the cysteine requirement of the body. Critically, under ma ny stressful conditions, the accompanying anorexia means that these new dem ands have to be met from the patient's protein stores. This sets up what is , in effect, an internal amino acid balance in which the supply (muscle pro tein) does not match the demand. The result is tissue loss and eventual mal nutrition. In our view, decisions as to whether specific amino acid supplem entation of the stressed patient will be beneficial should consider three c rucial questions. What should the supplement contain? How should it be admi nistered? At what stage should it be administered? Although we argue that t he first question may be close to being answered, the answers to the second and third still remain uncertain. Even so, there is a good case for the se rious consideration of the use of targeted amino acid supplements appropria te to the nature of different chronic conditions. (C) 2001 Harcourt Publish ers Ltd.