Protein metabolism in inflammatory bowel disease.

Major loss of body protein mass in inflammatory bowel disease is much less common than weight loss, which is often attributable to losses of other body, particularly water and fat. It does occur, however, in a few patients, especially in those with compromised food intake. It is due principally to the combined effects of diminished intake and excessive intestinal losses of amino nitrogen. Nitrogen metabolism is influenced not only by protein nutritional state and net nitrogen intake but also by disease activity. There is some evidence for abnormally low secretion of growth hormone in adolescents with inflammatory bowel disease and growth failure. Low serum albumin concentrations are not necessarily related to protein undernutrition and are the combined result of relatively reduced albumin synthesis, increased intestinal losses, and maldistribution between intravascular and extravascular spaces. Concentrations in the plasma of IgG and acute phase reactants may be raised despite increased losses into the bowel lumen. The prevention of total body protein depletion is achieved principally by maintaining adequate and often not supranormal intakes of a balanced source of amino nitrogen in a balanced diet given orally, enterally, or parenterally, combined with a medical or surgical approach to reduce disease activity: supranormal energy intakes are not beneficial.