Summary of main results

1. Total serum proteins, albumin, haemoglobin, and creatinine-height index remained constant, with averages of 7.0, 4.2,11.9, and 0.94, respectively.

2. Basal oxygen (VO2 ) consumption did not change. The averages for different nitrogen intakes, regardless of the source, were 107, 96, 104, and 97 per cent of expected. For nitrogen-free diets, the mean was also 97 per cent (mean ± S.D.: 48.5 ± 6.1 kcal/kg/ day). The respiratory quotient was also constant, the means being 0.88, 0.88, 0.82, 0.81, and 0.82 for the different nitrogen intakes. All variation was random.

3. Energy expenditure by insensible water loss determinations came to a mean of 74 kcal/kg/day for diets containing 0.5 g protein/kg/day or higher. For the nitrogen-free diet, it was 58 kcal/kg/day.

4. Weight changes are presented in figure 1 (mean and range). Weight loss in all subjects occurred only with the nitrogen-free diet. Prior to this period there was a consistent increase in skin-fold thickness.

FIG. 1. Mean and Range of Weight Changes in Four Pre-school Children Who Received Different Levels of Protein and 90 kcal/kg/day

5. Obligatory nitrogen losses are:

		mg N/kg/day	mg N/kcal/day
Integumentary	(mean ± S.D.) N = 8	5 ± 1	0.12 ± 0.02
Faecal	(mean ± S.D.) N = 8	19 ± 2	0.38 ± 0.03
Urinary	(mean ± S.D.) N = 8	36 ± 7	0.77 ± 0.17
Total	(mean ± S.D.) N = 8	58 ± 8	1.19 ± 0.21

6. Faecal nitrogen is consistently lower with egg than with the rice-soy-milk (RSM) mixture, by a mean of 4 mg/kg/day. Mean true digestibility for egg was 94 ± 5; for RSM, it was 91 ± 2. Urinary nitrogen was higher for egg protein than for RSM at intakes of 2.0 and 1.5 9 protein/kg/day, but at lower values the opposite occurred. Total integumentary nitrogen/kg/day obtained was as follows:

Nitrogen Intake	Egg Protein	RSM
320	10.4 ± 1.3 (9.6)*	8.0 ± 2.4 (7.3)
240	10.2 ± 1.2 (9.3)	6.6 ± 1.5 (5.7)
160	6.1 ± 0.8 (5.3)	6.5 ± 1.7 (5.6)
80	6.1 ± 1.3 t5.4)	5.9 ± 1.3 (5.1)
0	4.7 ± 0.6 (3.8)	4.7 ± 0.6 (3.8)

* (sweat and skin mean)

True nitrogen retention (mg/kg/day) obtained was as follows:

Nitrogen Intake	Egg Protein	RSM
320	58 ±16	94 ± 12
240	39 ± 15	52 ± 14
160	33 ± 18	22 ± 20
80	+2 ± 11	- 20 ± 15
0	-58 ± 8	-58 ± 8

7. Integumentary nitrogen correlated significantly with serum urea nitrogen (r = 0.56). Egg protein at different levels of intake, however, by producing greater changes in serum urea than RSM, also produced higher sweat and skin nitrogen losses.

Nitrogen in skin and sweat = 39.9 + 6.65 urea nitrogen (egg) r = 0.80
Nitrogen in skin and sweat = 51.3 ± 2.34 urea nitrogen (RSM) r = 0.41