Obligatory Urinary and Fecal Nitrogen Losses in Young Chinese Men

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Abstract
Fifty healthy Chinese male university students, 20 to 32 years of age and 42 to 75 kg body weight consumed daily for 14 days an essentially protein-free diet. Urine was analyzed daily for nitrogen (N) and creatinine, and fecal N was measured on pooled samples. The average for days 10 to 14 was taken as the obligatory urinary N loss. Obligatory urinary N was normally distributed, averaging (mean ± sd) 33.4 ± 4.2 mg N/kg body weight, 1.42 ± 0.15 g N/g creatinine, and 1.3 ± 0.2 mg N/basal kilocalorie, data which were significantly lower than for comparable Caucasians previously studied in the same manner at M.I.T. Obligatory fecal N was 13.1 ± 2.5 mg N/kg body weight, amounting to 28% of the total obligatory N loss. It was significantly higher than the value for the Caucasian subjects. However, the excretion data for the Chinese subjects were within the range of values reported from other studies with Caucasians. Statistically significant correlations were found between obligatory urinary N and body weight, basal metabolic rate, and creatinine. For nine subjects studied twice, once during a hot season and again during a cooler season, obligatory N loss was lower during the season of higher environmental temperature.