1. The capacity of the Chilean mixed diet to meet the daily protein and energy needs was tested in eight subjects aged from 20 to 31 years using the nitrogen balance method. This diet was tested at the protein levels of 0.40. 0.55 and 0.70 g/kg body-weight per d.
2. An egg reference diet providing 0.30, 0.45 and 0.60 g protein/kg per d was also assayed.
3. The mean daily energy intake was 207 kJ/kg per d according to subjects’previous intake and activity pattern.
4. The N balance response to each dietary protein level was taken as a measure of adequacy of protein intake, and regression analyses of N balance (Y) v. N intake (X) were calculated to estimate protein needs. The equations found were Y = 0.70X–68.7 for the egg diet, and Y = 0.74–92 for the mixed diet.
5. From these equations the mean protein requirements for equilibrium were estimated to be 0.61 g/kg for egg and 0.78 g/kg for the mixed diet.
6. If the coefficient of variation is 15, the protein requirement for N equilibrium of 97.5% of the population would be 0.8 g/kg per d for egg and 1.0 g/kg per d for the mixed diet.