Nitrogen balance of men with marginal intakes of protein and energy

J Nutr. 1975 Jul;105(7):914-23. doi: 10.1093/jn/105.7.914.


Present protein allowances are based on amounts of nitrogen (N) that maintain balance in adults in laboratory tests. In most tests of minimum N need, energy intakes were higher than present allowances and generally the participants maintained body weight or gained. To evaluate the relative importance of energy and protein intakes in the near-adequate range on the N equilibrium, healthy men were given two levels of protein with energy constant and three levels of energy with protein constant. In the first two 12-day periods, diets provided 5 and 7% of energy (E) from egg white protein with enough E to maintain weight essentially constant (39.6 plus or minus 4.4 kcal/kg). N balance data with these diets were used to select an individual protein intake level nearest to need (5, 6, or 7%), and that level was fed for the next three periods with the same E intake as before (100 E) and 85 or 115% of it. Crude N balance (dietary-fecal-urinary N) was minus0.26 g/day with 5% diet and 0.33 g/day with 7%. Balance was improved by 280 mg/g N fed between these levels. Predicted minimum N need to maintain crude N balance at 100 E is 89 plus or minus 18 mg/kg body weight or 3.76 plus or minus 0.61 mg/basal kcal. N balance fell to minus0.61 g/day with 85 E and increased to 0.59 g/day with 115 E. N balance changed by 174 mg/100 kcal between 85 and 100 E and 112 mg/100 kcal between 100 and 115 E. Energy intake appears to have a much greater effect on N balance than does protein intake in the marginally adequate ranges of intake.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Basal Metabolism
  • Body Height
  • Body Weight
  • Creatinine / urine
  • Dietary Proteins* / administration & dosage
  • Egg Proteins / administration & dosage
  • Egg White
  • Energy Metabolism*
  • Humans
  • Male
  • Nitrogen / metabolism*
  • Nutritional Physiological Phenomena
  • Nutritional Requirements
  • Urea / metabolism
  • Uric Acid / urine


  • Dietary Proteins
  • Egg Proteins
  • Uric Acid
  • Urea
  • Creatinine
  • Nitrogen