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close this bookProtein-Energy Requirements of Developing Countries: Evaluation of New Data (UNU, 1981, 268 p.)
close this folderResearch papers: Protein requirements-adults, standard protocols
close this folderCapacity of the Chilean mixed diet to meet the protein and energy requirements of young adult males
View the document(introduction...)
View the documentExperimental details
View the documentSummary of main results
View the documentConclusions
View the documentAcknowledgements

Summary of main results

Results of anthropometric changes are summarized in table 3. Tables 4 and 5 show the nitrogen-balance data. Urinary nitrogen excretion was greater with increasing nitrogen intakes from better diets. No correlation was found between faecal nitrogen, which included obligatory faecal nitrogen, and the level of protein intake for either protein. Faecal nitrogen excretion was significantly higher on the mixed diet (34 mg N/kg/day) than on the egg diet (18 mg N/kg/day) (p<0.001). This difference resulted in lower apparent nitrogen digestibility with the mixed diet (p < 0.001). Using 9 mg/kg/day as the obligatory faecal level, the mean true protein digestibilities of the two protein powders at three increasing levels of intake were 82.6, 89.1, and 92.8 per cent for egg and 71.4, 77.1, and 83.5 per cent for the mixed diet. Digestibility of the mixed diets was significantly lower (p < 0.001). Figure 1 shows the regression analyses of "true" nitrogen balance. The "pooled" regression equations are:

Egg diet y = -69.95 + 0.708 X, n = 24, r = 0.852
Mixed diet y = -91.95 + 0.737 X, n = 21, r = 0.807

TABLE 3. Anthropometric Changes in Subjects Participating in the Study

Subjects Body weight (kg) Waist (cm) Gluteal circumference (cm) Mid-upper left arm circumference (cm) Left triceps skin-fold (mm) Left subscapular skin-fold (mm)
J.A. Initial 55.0 72 85.0 26 5.6 8.4
Change -1.22 -0.5 -1.0 -0.5 0.2 0
H.F. Initial 54.5 72 84.5 25 5.0 6.4
Change +1.35 1.0 1.5 0 0.2 0
J.B. Initial 75.0 90 96 31 8.4 16.2
Change -0.27 - 1.0 0 0 0 0.2
O.G. Initial 60.7 80 89.5 25.5 5.5 11.2
Change +0.67 1.5 1.5 1.0 0.5 0.2
S.L. Initial 59.0 81 91 25.5 5.2 8.6
Change -0.22 0 0 0 0 0.2
H.R. Initial 60.5 79 90 24.5 6.2 10.6
Change +0.27 1.0 1.0 0.5 0.2 -0.2
E.R. Initial 61.5 80 88 27 5.6 7.4
Change - 0.97 -2.0 0 0 -0.2 -0.4
Mean S.D.  
Initial 60.96.8 79.16.1 89.13.9 26.42.2 5.91.2 9.83.3
Change 0.0550.9 0.01.3 0.40.9 0.10.4 0.10.2 0.00.2

TABLE 4. Nitrogen Balance and Nitrogen Digestibility of Individual Subjects Given an Egg Diet et three Dietary Levels of Nitrogen Intake

Subjects (mg/kg/day) Nitrogen intake Urinary nitrogen (mg/kg/day) Faecal nitrogen Nitrogen balance 1,2

(%)

Apparent

digestibility

J.A. 48 67.8 19.6 -44.4 59.2
H.F. 48 50.8 13.3 -21.1 72.3
J. B. 48 49.3 9.2 - 15.5 80.8
O.G. 48 53.4 18.5 - 28.9 61.5
S. L. 48 48.6 24.0 - 29.6 50.0
M.L. 48 77.0 21.8 -55.8 54.6
H. R. 48 70.1 25.0 - 52.1 47.9
E.R. 48 54.4 18.1 -29.5 62.3
Mean 48 58.9 18.7 -34.6 61.1
S.D.   11.0 5.3 14.6 11.1
J.A. 72 62.8 19.1 -14.9 73.5
H.F. 72 78.3 14.6 -25.9 79.7
J.B. 72 72.8 16.0 -21.8 77.8
O.G. 72 67.1 18.2 -18.3 74.4
S. L. 72 66.3 17.5 - 16.8 75.7
M.L. 72 62.5 20.0 - 1 5.5 72.2
H.R. 72 68.1 15.7 -16.8 78.8
E.R. 72 63.8 22.2 -19.0 69.2
Mean 72 67.7 17.9 - 18.6 75.2
S.D.   5.4 2.5 3.7 3.6
J.A. 96 72.0 22.6 - 3.6 76.5
H.F. 96 67.4 15.8 + 7.8 83.5
J.B. 96 72.2 14.5 + 4.3 84.9
O.G. 96 71.6 18.4 + 1.0 80.8
S. L. 96 77.5 20.8 - 7.3 78.3
M.L. 96 72.6 20.9 - 2.5 78.2
H.R. 96 74.5 18.9 - 2.4 80.3
E. R. 96 75.4 19.4 - 3.8 79.8
Mean 96 72.9 18.9 - 0.8 80.2
S.D.   3.0 2.7 4.9 2.8

1 Estimated "true" balance, assuming 5 mg N/kg/day for integumental and miscellaneous losses.
2 Since individual aliquots from diet periods varied less than 5 per cent of calculated intake based on nitrogen analysis of ingredients, nitrogen balance was computed from the latter.

TABLE 5. Nitrogen Balance and Nitrogen Digestibility of Individual Subjects Given a Chilean Mixed Diet at Three Dietary Levels of Nitrogen Intake

Subjects Urinary nitrogen Faecal nitrogen Nitrogen balance1 Apparent digestibility

(mg/kg/day)

(%)
Nitrogen intake 64 mg/kg/day  
J. A. 71.8 36.7 -49.5 42.6
H.F. 58.6 29.1 -28.7 54.5
J.B. 55.7 31.2 -27.9 51.2
O.G. 84.7 30.8 -56.5 51.9
S. L. 69.4 44.9 - 55.3 29.8
H. R. 74.6 38.8 -46.4 39.4
E. R . 69.1 29.2 -39.3 54.5
Mean 69.1 33.2 -43.4 46.2
S.D. 9.8 5.7 11.8 9.3
Nitrogen intake 88 mg/kg/day  
J. A. 75.2 40.0 -32.2 54 5
H.F. 69.5 38.8 -25.3 55.9
J. B. 65.4 30.5 - 12.9 57.5
O.G. 66.6 34.3 -17.9 61.0
S. L. 82.8 44.9 -44.7 43.1
H.R. 96.0 30.8 -43.8 65.0
E. R . 81.9 34.4 - 33.3 60.9
Mean 76.8 36.2 -30.0 56.8
S.D. 11.0 5.3 12.1 7.0
Nitrogen intake 112 mg/kg/day  
J. A. 84.1 35.4 -12.5 68.4
H . F . 78.1 35.0 - 6.1 68.7
J.B. 64.2 32.5 +10.3 71.0
O.G. 83.4 32.6 - 9.0 70.9
S. L. 73.4 43.4 - 9.8 61.2
H. R. 99.9 28.7 - 21.6 74.4
E. R. 80.0 34.4 - 7.4 69.3
Mean 80.4 34.6 - 8.0 69.1
S.D. 11.0 4.5 9.6 4.0

1 Estimated "true" balance, assuming 5 mg N/kg/day for integumental and miscellaneous losses.

Mean nitrogen requirements for equilibrium were estimated as 97 mg N/kg/day for the mixed diet. Based on the 95 per cent confidence bands about the regression, the safe levels of protein intakes would be 1.1 g/kg/day for egg and 1.5 g/kg/day for the mixed diet; assuming that the coefficient of variation would be 15 per cent, as suggested by the 1971 FAO/WHO Expert Committee, the safe levels of protein intakes would be 0.8 9 and 1.0 9 protein/kg/day for the egg and mixed diets, respectively.

Table 6 summarizes the results of total serum protein, albumin, blood urea nitrogen (BUN), serum glutamic oxaloacetic transaminase (SGOT), and serum glutamic pyruvate transaminase (SGPT). Significant changes relative to initial values were found



FIG. 1. Regression Analyses of "True" Nitrogen Balance in total serum protein and albumin values with the mixed diet (2-way ANOVA). Blood urea nitrogen decreased with both diets.