Abstract

A short-term N balance study was conducted In twelve healthy female adults aged 21-32 years to determine their protein requirement. Four dietary protein levels (0 3, 0-4, 0-5 and 0 6 g protein/kg per d) were used. Energy intake of the subjects were kept constant at 018 MJ/kgper d. All subjects maintained their normal activity throughout the study period. N excretion was determined from the measurements of N in a total collection of urine, faeces, sweat and menstrual fluid for each dietary period. N balance during the four protein levels were — 1515 (sd 5-95), -5-53 (sd 6-71), +615 (sd 4.76) and +12 05 (sd 8.63) mg N/kg per d for 0 3, 0 4, 0-5 and 0-6 g protein/kg per d respectively. The calculated average N requirements from regression analysis was 76 0 (sd 3 37) mg N/kg per d (0 48 g protein/kg per d). The estimate of allowance for individual variation to cover the 97 5% population was 95 mg N/kg per day(0-6 g protein/kg per d). The net protein utilization (NPU) of the diet was 0-55. When compared with a similar study with men, there was a significant difference in the protein requirement between sexes. Thus, the unjustifiable sex difference in the protein allowance recommended by the Food and Agriculture Organization/World Health Organization/United Nations University (1985) Expert Consultation group must be reviewed.