Protein requirements of young Chinese male adults on ordinary Chinese mixed diet and egg diet at ordinary levels of energy intake.

With a total of 28 normal, healthy male adults, N balance studies with both Chinese mixed diet and egg diet were conducted at four protein levels with the former (0.45, 0.55, 0.65 and 0.75 g . kg-1 . day-1) and at three protein levels with the latter (0.35, 0.45 and 0.55 g . kg-1 . day-1) at ordinary levels of energy intake. By regression analysis, the mean maintenance N requirement (PRm) of the mixed Chinese diet calculated was 127.0 mg . kg-1 . day-1 (0.79 g protein . kg-1 . day-1). Estimate a allowance for individual variation to cover the 97.5% population (PR0.975) was 188.1 mg . kg-1 . day-1 (1.18 g protein . kg-1 . day-1). As for the egg diet series, PRm and PR0.975 were 98.2 mg N . kg-1 . day-1 (0.61 g protein . kg-1 . day-1) and 141.6 mg N . kg-1 . day-1 (0.89 g protein . kg-1 . day-1), respectively. Net protein utilization (NPU) of egg diet protein was significantly higher than that of the Chinese mixed diet protein (P less than 0.01), with mean values of 56 versus 43. True digestibility of the mixed diet and egg diet proteins was 96.5 and 98%, respectively. The efficiency of utilization of the Chinese mixed diet protein was 73-77% of the egg protein, based on relative N requirements.