SummaryThe effects of sulfur-containing amino acids (SAA) and potassium (K) on urinary excretion and retention of calcium (Ca) of 27 young Japanese women were studied. A basal diet low in protein level (50g per day) was fortified by meat or soy protein isolate (SPI) to a protein level of 100g per day, and effects of addition of apple to these high protein diets, and addition of SAA and/or potassium (K) to the high SPI diet, especially on urinary Ca excretion, were studied. The addition of meat which increased protein intake to 100g caused the increase in apparent absorption and urinary excretion of Ca with increased excretion of urinary sulfur (S), phosphate, ammonia, and titratable acids (TA), whereas addition of SPI did not. The addition of apple to high meat diet decreased absorption and urinary excretion of Ca. Urinary Ca, S, K, ammonia, and TA excretion increased by the addition of SAA to high SPI diet in a manner similar to the meat diet. Consequently, SAA-supplemented diet had a significantly negative effect on Ca retention. In SPI+SAA, K diet period, urinary K excretion markedly increased, and increments in urinary Ca, ammonia, and TA excretion were reversed. These changes observed in SPI+SAA, K diet period were similar to those by adding apple to meat diet without any effect on Ca absorption. The results suggest that the hypercalciuria induced by high meat diet is mainly caused by high content of SAA and may be reversed by the ingestion of K-rich foodstuffs, and soy protein does not induce hypercalciuria because of it contains less SAA than animal protein.

SummaryUtilization 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 100mg 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, 100mg N/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 91mg 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%. Key Words protein utilization, protein requirement, egg protein, wo men, energy intakeThe present protein allowance suggested by the FAO/WHO (1) and the Committee on Nutrition (Japan) (2) is based on the amount of dietary protein needed to maintain the nitrogen (N) balance in healthy male adults in laboratory

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