The effects of varying energy and nitrogen intake on nitrogen balance, body composition, and metabolic rate.
Body protein content (as measured by N balance) is normally regulated at a constant level, but is influenced by the level of both energy and N intake. Energy and N act synergistically on N balance. Not all forms of energy are equally effective in maintaining zero N balance; approximately 500 kcal of carbohydrate are required daily by the brain, and this minimum amount of dietary carbohydrate cannot be replaced by fat without loss of body N. Acute illness is accompanied by a catabolic state and an increase in the minimum N intake required for zero N balance. Nutritional depletion induces a metabolic state similar to that typical of growing organisms, in that N can be retained at zero energy balance. BMR includes essential thermogenesis and facultative thermogenesis. In addition, food has a specific dynamic action; it increases metabolic rate. Nutrient-induced increases in metabolic rate are exaggerated in acutely ill patients, such that large amounts of IV glucose may constitute a metabolic stress when given to patients. Equivalent N sparing can be obtained when as much as half of the glucose calories are replaced by fat calories. N balance is an incomplete index of nutritional status, and important information may be gained from measurements of body composition of acutely ill patients; in particular, the degree of expansion of ECW may predict outcome.
Edens
N K
NK
Gil
K M
KM
Elwyn
D H
DH
D000208:Acute Disease; D000596:Amino Acids / Q000378:metabolism; D001481:Basal Metabolism; D001823:Body Composition / Q000187:drug effects; D001833:Body Temperature Regulation; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004044:Dietary Proteins / Q000378:metabolism; D002149:Energy Intake; D004734:Energy Metabolism; D005110:Extracellular Space; D005947:Glucose / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism; D008659:Metabolic Diseases / Q000209:etiology; D009584:Nitrogen / Q000378:metabolism*; D010288:Parenteral Nutrition; D011506:Proteins / Q000378:metabolism; D014882:Water-Electrolyte Balance
D000596:Amino Acids; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D011506:Proteins; D005947:Glucose; D009584:Nitrogen