Infection and malnutrition

Malnutrition and infection operate in a vicious mutual synergism. Malnutrition predisposes to infection and increases the severity and mortality of infections. Infection reduces nutrient intake, interferes with substrate utilization and promotes tissue breakdown. Malnutrition and infection tend to occur in the same populations: resource-poor settings, poverty, and extremes of age are major risk factors; hospitalized patients are also at significant risk. A history of weight loss is an important indicator of macronutrient deficiency. Body mass index (BMI) is a useful indicator of wasting and mid-upper arm circumference of protein malnutrition. More complex body composition tools are available but blood tests are difficult to interpret in the presence of an acute-phase response. Infection impairs the ability of the body to utilize energy and protein/amino acids thus nutrition support should be tailored to meet but not exceed requirements in the acute phase. Recovery from infection is often associated with significant anabolism; during this phase nutrient requirements may increase dramatically.