Protein requirements of man: variations in obligatory urinary and fecal nitrogen losses in young men
Scrimshaw, N.S.; Hussein, M.A.; Murray, E.; Rand, W.M.; Young, V.R.
Journal of Nutrition 102(12): 1595-1604
1972
ISSN/ISBN: 0022-3166 PMID: 4634993 Document Number: 54643
For 14 days 83 healthy white men students, 18 to 26 years of age and of 58 to 104 kg bodyweight, ate daily either protein-free diet (44 men) or one supplying 0.1 g egg protein/kg bodyweight (39 men). Body cell mass (BCM) was calculated from whole body 40K in 37 men chosen at random. N and creatinine were estimated daily in urine and N was estimated in pooled faeces. Urinary N output reached a steady state between days 3 and 8 for all men; the average for days 10 to 14 was taken as the measure of obligatory urinary N loss. Mean urine and faecal N losses were not significantly different for the 2 diet groups and the data were combined for overall analysis. Obligatory urine N was normally distributed, averaging 37.2 plus or minus 5.5 mg N/kg bodyweight, 76.8 plus or minus 12.5 mg N/kg BCM, 1.8 plus or minus 0.30 mg N/basal kcal. Obligatory faecal N was 9 plus or minus 2 mg N/kg bodyweight, amounting to 20% of the total obligatory N loss. Although there were significant relations between obligatory urinary N and bodyweight, BCM, basal metabolic rate, and creatinine, they accounted for little of the variation in daily loss among individuals. Four men were studied after a 3-year interval; obligatory urinary N loss/kg bodyweight did not differ significantly between the 2 periods.