New appreciation of nitrogen balance obtained from Japanese navy data

In 1943, one of the authors (Miura) worked on the nutritional study of Japanese navy sailors. Fortunately the raw data of this study were conserved in secret in the private file of Miura. Recently, another author (Hashimoto) was seeking the data concerning nitrogen balance of Japanese people. Miura, recalling the remaining of the old data; he picked up the records of nitrogen metabolism of three sailors (A, B and C). Subject A, 34 years old, showed a net nitrogen balance of 77 g of protein per day; whereas subject B, 20 years old and subject C, 15 years old showed positive nitrogen balance. The authors remarked the relationship between unabsorbed nitrogen and nitrogen balance: The unabsorbed ratio of food nitrogen was the greatest in A (29%), but in B (22%) and C (19%) showed rather low ratio. Recent study using tracers, revealed that some amino acids, especially unabsorbed leucine in the intestine, might act as regulators of nitrogen balance in adults.