Conclusions and comments

1. The results of obligatory nitrogen losses in this study of adult Thai males were quite similar to those that have been reported on 4 Indian men, on 13 men studied at the University of California, on 9 Nigerian men, and in 83 studies on MIT students and 50 Chinese studies on males. It seems, therefore, that the obligatory urinary and faecal nitrogen excretion of young men, expressed as mg/kg/day, does not differ among ethnic groups.

2. Factorial calculation of safe levels of protein intake, using a correction factor of 1.3 and adding another 30 per cent for individual variability, as suggested in 1973 by FAO/WHO, results in 0.56 g/kg/day, which is almost identical to the safe level of intake recommended by FAD/WHO. That recommendation has recently been questioned for populations at large or for long-term studies. Our own studies using multi-level nitrogen balance techniques indicate that 0.56 9 protein/kg/day is too low (see Tontisirin et al., this volume).

Acknowledgements

This study was supported by the research fund of the World Hunger Programme of the United Nations University. We would like to thank Dr. V. Tanphaichitr for medical care of the subjects, the staffs of the clinical research ward and food analysis laboratory, Ramathibodi Hospital, for their assistance, and the subjects who cooperated throughout the study.