Conclusions and comments

1. Our results coincide with those obtained in the US and Taiwan, indicating that obligatory nitrogen losses are independent of ethnic and environmental conditions.

2. The correction factor of 1.3 used in factorial calculations underestimates protein requirements, as indicated by our studies using multi-level nitrogen balance techniques (see Young et al., this volume)

3. The relatively higher obligatory faecal nitrogen losses suggest that endogenous nitrogen excretion may be increased in subjects from developing regions with poor environmental sanitation and chronic, subclinical intestinal mucosal damage. Prolongation of the nitrogen-free diet showed a decrease in faecal nitrogen of about 50 per cent. That decrease might have been due to a further decline in labile nitrogen or to changes in the gut flora that contributed to faecal nitrogen losses.

4. Our subjects had higher energy intakes than are customary in this type of study. The men with low weight/height indices had higher energy intakes per unit of body weight.

5. Weight losses may have been due to losses in lean body tissue, mainly muscle, as suggested by the drop in mean daily urinary creatinine excretion.

6. The excessive energy intake decreased the urinary nitrogen losses, especially during the last four days. The men had stable physical energy patterns. The effect of energy balance deficit can be anticipated to raise obligatory nitrogen losses. Nevertheless, the biological significance of excess energy appears to be minor.

Acknowledgements

The authors gratefully acknowledge Laboratories Pfizer de Chile for supplying the vitamin/mineral supplement (Polyterra) used in this experiment.