Requirement and utilization of egg protein by Japanese young men with marginal intakes of energy

The effect of marginal intakes of energy on the requirement and utilization of egg protein was evaluated in 46 Japanese young men. The subjects were given a standard diet for 1 week and then low protein diets for 2 weeks. These diets contained about 32, 64, and 80 mgN/kg with whole eggs as the protein source. In the first experiment with excess energy, the energy intakes of 31 subjects were kept constant during the 3 week experiment, the mean intakes being 48.2 +/- 1.5 kcal/kg. The body weight was affected by changing protein intakes while maintaining energy intakes at 48 kcal/kg. From regression analysis, the N requirement for apparent N equilibrium was estimated to be 82.0 +/- 8.0 mgN/kg, where NPU was calculated as 56. In the second experiment with submaintenance energy, 15 subjects received 40 kcal/kg. The N requirement was 124 +/- 21 mgN/kg, where NPU was calculated as 37. From these results and those of previous studies, it was concluded as follows: 1) N balance and NPU were remarkably affected by energy intake changed around maintenance level; and 2) the NPU for egg protein in young men for maintenance intakes of energy and N is about 50 to 55. For estimation of the protein requirement for Japanese adults, a correction factor of 100/55 (about 1.8) was used instead of 1.3 adopted by the 1973 FAO/WHO.