PROTEIN-ENERGY REQUIREMENTS OF BOYS 12-14-Y-OLD DETERMINED BY USING THE NITROGEN-BALANCE RESPONSE TO A MIXED-PROTEIN DIET

Short-term nitrogen-balance response to graded intakes of a vegetable mixed-protein diet and to a milk-egg protein diet was tested in eight healthy male children aged 12-14 y. They received 72, 104, 136, and 168 mg N . kg body wt-1 . d-1 for 10 d while on the mixed diet, and 160 mg N . kg-1 . d-1 on the milk-egg diet. The mean regression equation was nitrogen balance = 0.64(nitrogen intake) - 74, all values are in mg N . kg-1 . d-1. Apparent digestibility was 86% and 85% for the mixed and milk-egg diets when the subjects received 168 and 160 mg N . kg-1 . d-1, respectively. Mean nitrogen intake for satisfactory nitrogen retention for growth on the mixed diet was 147 mg N . kg-1 . d-1; the recommended protein allowance to cover 97.5% of the population, which was derived by using a CV of 12.5%, is 1.15 g protein . kg-1 . d-1. We conclude that FAO/WHO/UNU recommendations are adequate, at least for short-term nitrogen retention; long-term studies are needed to evaluate the chronic safety of this protein allowance.