Protein Metabolism in Response to Injury and Other Pathological Conditions

The preceding two papers in this series describe the regulation of protein metabolism in man (MUNRO 1974a) and the impact of food intake on his protein metabolism (MUNRO 1974b). This final paper deals with the effects of some important disease processes, notably infection and injury, on protein metabolism, and the nutritional implications of these changes. Acute infections, injury and many other diseases give rise to loss of body protein, and, in consequence, protein from the diet must be retained in order to restore the body to its previous state. Some of these conditions, such as non-specific stresses, respiratory infections, and temporary gastrointestinal infections are so common that the amounts of protein needed to restore the protein content of the body could be regarded as a requirement of everyday living. Other conditions, such as fractures, burns and liver damage may not occur to an individual during his whole lifetime, and dietary treatment during the course of such illnesses is part of the therapy administered by the physician or surgeon, and can be a major factor in survival requiring special measures such as parenteral nutrition. The clinical recognition of undernutrition can be demanding; for example, SHINABERGER & GINA (1968) describe patients on renal dialysis who were unable to maintain their serum albumin levels on an otherwise adequate intake of protein (0.75 g/kg) when they suffered an infection, operation, etc. The authors comment that “this level of protein intake permits no nutritional reserve capacity to buffer a catabolic state”.