Obligatory urinary and faecal nitrogen losses in young Chilean men given two levels of dietary energy intake

Abstract

1. The obligatory nitrogen losses were measured in young adult males of the low socio-economic group, consuming an N-free diet at 192 kJ (46 kcal)/kg per d from day 1 to 10 and 243 kJ (58 kcal)/kg per d from day I I to 18.2. All subjects, except one, lost weight compatible with N loss. 3. A kinetic evaluation of the results showed that the asymptotically derived urinary N loss after stability had been reached was 35.8 mg N/kg per d. The mean time to stability was 6.5 d. The subjects showed a trend toward decline in N loss while consuming the high-energy N-free diet.4. The obligatory faecal N loss for days 1-10 was 16.1 mg N/kg $r d and 8 mg N/kg per d for days 11-18. 5. Based on the factorial approach the total obligatory N loss of our subjects, for the initial 10 d, was 57.5 mg N/kg per d.

Studies on nitrogen metabolism in rats of different age fed on a protein-free diet. 4. Urinary urea nitrogen excretion in relation to body size and duration on protein-free diet feeding

“…The urea in urine from animals fed protein-containing diets is derived from two sources, urea from deamination of ingested protein and urea from catabolism of endogenous proteins. In nutritional studies, endogenous urea has been determined rarely, usually only once, during the so called period of stabilized urinary nitrogen excretion in humans and animals given a protein-free diet (Smith, 1926;Kiriyama and Ashida, 1964;Berdanier et al, 1967;Calloway and Margen, 1971;Uauy et al, 1982).…”