Utilization and Requirement of Egg Protein in Japanese Women

Abstract

Utilization and requirement of egg protein in Japanese women with two levels of energy intake were estimated. In experiment 1, fifteen female students were given semi-purified diet containing whole egg as the sole nitrogen source for 12 days. Nitrogen intakes were 50 for five, 75 for two and 100 mg N/kg for eight subjects. Habitual energy intake was determined individually by detailed inquiry about the foods consumed before the experiment was started. Mean energy intake was 33 kcal/kg. In experiment 2, eighteen other subjects were given the same diet containing four intake levels of egg protein (30, 50, 75, 100mgN/kg) with an energy intake of about 100 kcal/day added to that calculated by the food intake inquiry. The mean energy intake was 37 kcal/kg. The total nitrogen contents of the experimental diet, urine and feces were analyzed and the nitrogen balance was estimated from these figures. Significant rectilinear relations were found between nitrogen intake (X, mg N/kg) and balance (Y, mg N/kg). The regression equations were;
Experiment 1: Y=0.256X-34.4 (n=15, r=0.742)
Experiment 2: Y=0.326X-29.7 (n=18, r=0.645)
The maintenance intakes of whole egg protein for apparent nitrogen equilibrium were calculated to be 134 and 91 mg N/kg with energy intakes of 33 and 37 kcal/kg, respectively. Net protein utilization (NPU) and digestibility of egg protein were calculated using the obligatory N losses previously determined in Japanese women. The NPUs at the maintenance level of egg protein with energy intakes of 33 and 37 kcal/kg were estimated as 31 and 47, respectively. The mean digestibility of egg protein was 96%.