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Two 60-day N-balance studies with 14 young male MIT students were conducted to determine the effect of meal composition and pattern on the efficiency of dietary N utilization. Two levels of daily energy intake, one sufficient to maintain body weight and the other 80% of this level, were studied during each of two 30-day diet periods. Nonfat milk was the sole dietary protein source and provided 0.5 g/kg per day in experiment 1 and 0.4 g/kg per day in experiment 2. For 15-day diet periods at each energy level in experiment 1, protein was divided either equally among three meals (breakfast, lunch, and dinner) or two meals (lunch and dinner) with breakfast being “protein-free.” The distribution of energy intake among the different meals remained constant throughout the experiment. In experiment 2, the daily protein intake was divided among either two or three meals, but here the breakfast meal was omitted entirely when protein was provided only at lunch and dinner. Thus, the distribution of both protein and energy intake was varied among the meals in this experiment. In both experiments, and with each level of energy intake, the distribution of protein among meals did not significantly affect N balance. These results indicate, for levels of protein intake near maintenance requirements, that the distribution of protein among daily meals is not a significant factor in the efficiency of N utilization by young men.

Six young adult male subjects participated in an experiment designed to determine the effect of diet consistency per seon nitrogen utilization. A diet of conventional foods supplying 1 gm. protein per kg. was fed in solid form for six day adaptation and experimental periods. During the next six day period the same diet was homogenized with water to the consistency of a thick milk shake. For the final six day period the solid diet was again provided. Total water, protein and caloric intake remained constant during the entire experimental period. Urinary nitrogen, creatinine, total urinary volume and specific gravity were measured daily during the periods of liquid and solid diets. Fecal nitrogen excretion was determined on three day pooled samples. There was no measurable effect of the consistency of the diet on the utilization of dietary nitrogen. Psychologic tests made on the subjects during the experimental periods did not detect changes due to consistency of the diet. The results support the use of liquid diets in nitrogen balance experiments in man.