Search

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.

Short-term nitrogen-balance response to a vegetable-protein mixed diet and to a milk-egg protein diet was tested in eight healthy male children 8-10 y old. They received 96, 128, 160, and 192 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 = 0.52 (nitrogen intake) -68.3, all in mg N.kg-1.d-1. Apparent nitrogen digestibility was 82% and 86% for the mixed and milk-egg diets, respectively, when the subjects received 160 mg N.kg-1.d-1. Mean nitrogen intake for satisfactory nitrogen retention on the mixed diet was 150 mg N.kg-1.d-1; the suggested protein recommended allowance to cover 97.5% of the population was derived by using a CV of 12.5% is 1.2 g protein.kg-1.d-1. We conclude that present recommendations are adequate for short-term nitrogen retention; long-term studies are needed to evaluate the chronic safety of this protein allowance.

The effect of energy supplementation was evaluated in six underweight adults under free-living conditions. Customary energy intake (EI) over 4 wk and estimated body composition were defined. Then for 12 wk subjects were fed their customary EI under controlled conditions to assure stable energy reserve. Finally, intake was increased by a mean of 720 kcal/d for 8 wk adjusted to increase body fat from 9 to 18%. Body weight (means +/- SD) increased from 55.2 +/- 3.4 to 57.0 +/- 4.2 kg. Body fat gain was highly variable ranging from 0.6 to 3.8 kg. Energy expenditure (EE) by the factorial and doubly labeled water methods did not change. Fat storage accounted for 66% of the supplemental energy; 237 kcal/d remained unaccounted for. EE by the factorial method, which uses indirect calorimetry or isotopic measurements, were highly correlated (r = 0.8; p less than 0.01). Under the conditions of this study EI does not affect EE. The labeled water method permits the evaluation of energy expenditure in free-living conditions.