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Nitrogen balance in children

27. Protein needs of chilean pre-school children fed milk and soy protein isolate diets
28. Protein requirements of Filipino children 22-29 months old consuming local diets
29. Long-term study on the adequacy of usual Thai weaning food for young children

27. Protein needs of chilean pre-school children fed milk and soy protein isolate diets

Juan Ignacio Egana M, Angel Fuentes, and Ricardo Uauy

Institute of Nutrition and Food Technology (INTA), University of Chile, Santiago 11, Chile

Objectives

1. To determine the protein requirements of Chilean pre-school children fed milk or soy isolate diets.

2. To evaluate the protein quality of soy protein isolate (SPF-200) in comparison with the protein of milk.

Experimental Details

Subjects

Seven healthy pre-school children consuming two sources of protein; their individual characteristics are given in table 1.

Study Environment

Location: Institute of Nutrition and Food Technology, Clinical Research Center Metabolic Ward. Climate: moderate, 15s-25s, C.

Physical Activity

All children maintained their normal physical activities.

Diets

Both proteins were given as formula and solid food. They were fed at 1.5, 1.25, 1.0, and 0.75 g/kg day (a typical diet is shown in table 2). Energy intake was calculated from proximate composition and Atwater factors.

TABLE 1. Individual Characteristics of Seven Pre-school Children Participating in the Study

Subject Age
(months)		 Weight
(kg)		 Height
(cm)		 Weight: Height
Ratio
(%)
J.L. 38 13.80 95.0 98
M.A. 36 12.90 90.0 98
M.C. 43 14.00 92.0 97
R.D. 56 18.25 103.0 109
J.C. 46 13.20 92.0 97
E.R. 34 12.60 83.0 108
A.B. 62 18.90 108.0 104
Mean 45 14.81 96.4 101.6
SD 10.5 2.63 8.9 5.3

TABLE 2. Composition of SPF-200 Diet Fed at 1.5 g/kg to a 10 kg Child

Ingredient Amount
(g)		 Energy
(kcal)		 Protein
(g)		 CHO
(g)		 Fat
(g)
SPF-200 16.50 61.49 14.37 - -
Potato starch 13.80 45.81 0.02 11.39 0.01
Sugar 47.60 183.26 - 47.36 -
Maltose-dextrin 33.00 126.06 0.29 31.35 -
Corn oil 27.00 238.68 - - 27.00
Margarine 2.00 14.40 - - 1.62
Corn starch 37.00 129.87 0.14 32.07 0.07
Strawberry-flavoured maltose dextrin 20.00 79.20 0.02 19.76 -
Honey 17.80 40.94 0.03 10.55  
Orange-flavoured beverage 15.00 77.46 0.01 19.20  
Flavourings 1.38 3.50 0.15 0.20 0.23
Water 963.00 - - - -
Total per day   1,000.67 15.03 171.88 28.93
Total per kg/day   100.00 1.50 17.10 2.89

TABLE 3. Nitrogen Balance and Nitrogen Digestibility of Individual Subjects Given a SPF-200 Diet at Four Dietary Levels of N Intake (mg/kg/day)

N intake Subject Faecal N Urinary N N Balance Digestibility
240 A.L. 32.7 134.0 73.2 86.4
M.A. 44.6 125.4 70.4 81.5
J.L. 27.2 112.8 100.2 88.7
M.C. 20.6 148.9 70.5 91.4
J.C. 39.3 174.1 26.7 83.6
R.D. 33.8 150.5 54.1 85.8
E.R. 33.2 158.2 48.6 86.2
Mean 33.1 143.4 63.4 86.2
SD 7.8 20.8 23.1 3.2
200 A.B. 40.2 110.4 48.9 80.0
M.A. - - - -
J.L. 33.3 112.2 54.9 83.4
M.C. 25.5 137.4 37.3 87.4
J.C. 35.3 141.8 23.0 82.4
R.D. 39.4 134.8 25.7 80.3
E. R. 25.6 110.4 70.6 87.8
Mean 33.2 124.5 43.4 83.6
SD 6.5 15.0 18.3 3.4
160 A.B. 48.9 91.6 19.9 69.5
M.A. 28.1 104.9 27.6 82.5
J.L. 21.3 87.4 52.4 86.9
M.C. 26.4 108.5 25.2 83.5
J.C. 22.0 116.2 23.0 86.2
R.D. 35.3 103.1 21.6 77.9
E.R. 32.2 92.1 35.6 80.0
Mean 30.6 100.5 29.3 80.9
SD 9.5 10.5 11.4 6.0
120 A.B. 39.3 75.9 4.7 67.2
M.A. 19.6 89.9 10.2 83.6
J.L. - - - -
M.C. 47.4 67.0 4.4 59.9
J.C. 40.7 92.0 - 13.9 65.8
R.D. 32.8 91.3 - 4.1 72.6
E.R. 38.4 81.8 - 0.2 68.0
Mean 36.4 83.0 0.18 69.5
SD 9.5 10.0 8.43 8.0

TABLE 4. Nitrogen Balance and Nitrogen Digestibility of Individual Subjects Given a Milk Diet at Four Dietary Levels of N Intake (mg/kg/day)

N intake Subject Faecal N Urinary N Balance N Digestibility
- A.B. 54.0 105.2 81.0 77.5
M.A. 26.6 122.8 90.0 88.9
J.L. 22.5 103.2 125.5 90.6
M.C. 56.6 117.1 66.3 76.4
J.C. 38.1 126.8 75.1 84.1
R.D. 53.7 93.8 92.5 77.6
E.R. 32.0 112.0 96.0 86.7
Mean 40.5 111.6 89.6 83.1
SD 14.2 11.6 19.0 5.9
200 A.B. - - - -
M.A. 26.1 104.5 69.7 87.0
J.L. 31.4 74.3 93.5 84.2
M.C. 59.7 101.7 38.0 70.1
J.C. 46.5 100.6 52.8 76.7
R.D. 55.5 78.4 66.1 72.2
E.R. 36.2 92.2 71.7 81.9
Mean 42.6 92.0 65.3 78.7
SD 13.5 12.8 18.7 6.8
160 A.B. - - - -
M.A. 22.3 83.5 54.8 86.1
J.L. 26.9 54.9 77.9 83.2
M.C. 51.8 80.7 28.3 67.8
J.C. 35.8 82.0 42.2 77.6
R.D. 50.6 63.9 45.6 68.4
E.R. 39.2 72.3 48.3 77.5
Mean 37.8 72.9 49.5 76.8
SD 12.0 11.5 16.4 7.5
120 A.B. - - - -
M.A. 30.4 59.0 31.1 74.8
J.L. 22.1 50.0 53.2 81.6
M.C. 33.0 66.7 20.3 72.5
J.C. 47.1 82.1 - 2.5 60.7
R.D. 24.3 67.0 28.7 79.8
E.R. 25.4 59.2 35.4 78.9
Mean 30.4 64.0 27.7 74.7
SD 9.1 10.9 18.4 7.6

TABLE 5. Regression Equations of Apparent Nitrogen Retention (y) on Nitrogen Intake (x) of Soybean Protein Isolates: y = a + bx

Subject a b r
A.B. - 68.9 0.59 0.95
M.A. - 48.1 0.49 0.93
J.L. - 57.5 0.63 0.75
M.C. - 59.0 0.52 0.85
J.C. - 41.0 0.31 0.76
R.D. - 56.9 0.45 0.81
E.R. - 46.4 0.47 0.76
Mean - 54.0 0.49  
SD 9.4 0.10  
Pooled data - 57.2 0.51 0.77

TABLE 6. Regression Equations of Apparent Nitrogen Retention (y) on Nitrogen Absorption (NA) of Protein Isolates: y = a + b NA

Subject a b r
A.B. - 39.9 0.55 0.96
M.A. - 50.1 0.62 0.93
J.L. - 54.8 0.72 0.80
M.C. - 29.7 0.43 0.85
J.C. - 35.0 0.34 0.83
R.D. - 43.6 0.46 0.82
E.R. - 30.2 0.46 0.80
Mean - 40.3 0.51  
SD 9.6 0.13  
Pooled data - 40.3 0.51 0.79

TABLE 7. Regression Equations of Apparent Nitrogen Retention (y) on Nitrogen Intake (I) of Milk: y = a + bI

Subject a b r
A.B. - - -
M.A. - 25.8 0.49 0.93
J.L. - 17.0 0.58 0.91
M.C. - 28.3 0.37 0.81
J.C. - 63.8 0.59 095
R.D. - 37.1 0.53 0.94
E.R. - 29.4 0.51 0.96
Mean - 33.6 0.51  
SD 16.2 0.08  
Pooled data - 37.6 0.53 0.77

TABLE 8. Regression Equations of Apparent Nitrogen Retention (y) on Nitrogen Absorption (NA) of Milk: y = a + b NA

Subject a b r
A.B. - - -
M.A. - 11.7 0.48 0.93
J.L. - 3.5 0.59 0.91
M.C. - 22.9 0.47 0.84
J.C. - 37.5 0.58 0.97
R.D. - 32.2 0.68 0.93
E.D. - 15.7 0.54 0.96
Mean - 20.6 0.56  
SD - 12.8 0.08  
Pooled data - 24.8 0.59 0.85

TABLE 9. Changes in Biochemical Indices for Subjects in SPF-200 and Milk Study


 SPF-200 Paired t Milk Paired t
Initial Final t P < Initial Final T P <
Total protein (g/dl) 6.85a 6.68 0.2 NS 6.84 6.76 0.1 NS
0.23 0.48     0.25 0.40    
Albumin (g/dl) 4.50 4.21 1.2 NS 4.45 4.37 0.3 NS
0.43 0.32     0.45 0.25    
Globulin (g/dl) 2.35 2.46 0.0 NS 2.38 2.39 0.0 NS
0.52 0.51     0.56 0.42    
BUN (mg/dl) 10.07 8.76 0.9 NS 10.4 6.56 1.9 NS
3.80 1.74     4.1 0.75    
Creatinine (mg/dl) 0.34 0.53 1.2 NS 0.34 0.46 1.2 NS
0.06 0.17     0.07 0 07    
Total lipids
 507.1 472.4 1.01 NS 509.7 469.5 2.15 NS
40,0 106.8     43.2 71.9    
Triglycerides
 74.8 61.7 6.9 0.001 75.0 61.8 1.2 NS
35.8 9.6     39.2 18.5    
Cholesterol
 144.1 115.9 3.9 0.12 146.6 132.1 1.4 NS
14.1 20.3     15.2 27.6    
SGOTa
 42.6 256.0 2.0 NS 44.8 243.5 2.6 0.05
15.4 276.0     19.9 141.5    
SGPT
 13.4 143.0 29.9 0.0001 14.0 80.0 22.6 0.0001
5.6 173.0     5.9 50.0    

a. Mean + SD.

TABLE 10. Haematologic Values of Subjects in SPF-200 and Milk Study (mean + SD)

  SPF-200 Paired t Milk Paired t
Initial Final t P < Initial Final t P <
Haemoglobin
(g/dl)		 12.4 12.4 0.2 NS 12.3 12.6 0.6 NS
0.4 0.6     0.2 0.8    
Haematocrit
 37.4 36.1 2.9 0.09 37.3 36.9 0.6 NS
1.2 2.3     1.2 2.3    
WBC (mm³) 11,513 8,629 2.7 0.05 11,923 9,272 1.2 NS
4,674 2,822     4,980 1,982    
PMN 4,969 3.233 2.4 NS 4,817 4,057 1.5 NS
1,360 1,148     1,422 1,317    
Lymphocytes 5,509 4,704 0.64 NS 6,065 4,465 0.9 NS
4,459 1,968     4,611 1,024    

Experimental Design

Four balance periods were used. Each period consisted of a four-day adaptation period and a four-day collection period. Decreasing levels of N intake were used.

Nitrogen Balance

The nitrogen content of the diet, urine, and faeces was measured by the macro-Kjeldahl technique. Urinary urea. creatinine. and total N were determined daily. Faecal N corresponded to a four-day pool.

Anthropometric Indices

Weight, height, arm circumference and skinfold measurements were taken before and after each level of N intake.

Summary of the Main Results

Nitrogen Balance

Individual apparent nitrogen balances are shown in table 3 for soybean isolate and in table 4 for milk. Mean apparent digestibility for soybean isolate ranged from 70 to 86 per cent. and for milk 75 to 83 per cent, corresponding to high and low nitrogen intakes. Apparent nitrogen balance ranged from 0.0 to 63 for soybean and from 28 to 90 mg/kg/day ,or milk.

Regression Equations

The individual and mean regression equations relating the N retained with the N intake and N absorbed appear in tables 5 and 6, respectively, for soybean isolate, and in tables 7 and 8 for milk.

Individual regressions of daily nitrogen balance were significantly positive. Mean regressions of N balance on NI were NB = 0.49 NI - 54 for soybean isolate and 0.51 NI - 34 for milk. The slopes were not significantly different. Nitrogen intake needed to retain 24 mg N/kg daily was considered requirement.

Biochemical Indices (tables 9 and 10)

Non-significant decreases in serum albumin, urea. and lipids were observed. A significant increase in amino transferases was noted at the lowest NI for both proteins.

Anthropometric Indices

These showed non-significant changes over the period evaluated, except for weight gain while consuming milk was consumed.

Conclusions

Soybean protein isolates showed similar digestibility but lower utilization compared with milk protein at the range of intakes studied. Mean daily protein intakes to retain 24 mg/kg/day nitrogen were 0.99 and 0.71 g/kg/day for soybean protein isolate and milk, respectively.

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