The relationship between serum urea levels and dietary nitrogen utilization in young men

Abstract

1. Results from metabolic balance studies in young adult men were examined for the relationships between the concentration of serum urea (SUN) and the efficiency of dietary nitrogen utilization. A total of 231 separate balance periods were included in the analysis. Net protein utilization (NPU) was used as an index of dietary protein quality. 2. Protein intake ranged from 0·27–0·73 g/kg body-weight per d in the various experiments. There was a highly significant negative correlation between NPU and urea levels. The relationship was: NPU = 1·23–0·029 × SUN (mmol/l) ( r = −0·89). 3. These results are considered in relation to the evaluation of protein quality in adult humans.