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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 folderProtein requirements for young Colombian adults consuming local diets containing primarily animal or vegetable protein
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View the documentObjectives
View the documentSummary of the main results
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(introduction...)

Objectives
Summary of the main results
Conclusions

Luis F. Fajardo, Oscar Bolanos, Giovanni Acciarri, Fanny Victoria, Jaime Restrepo, Ana B. Ramz, and Luz M. Angel
Escuela de Medicina, Universidad del Valle, Cali, Colombia

Objectives

These studies were designed to determine the level of protein intake necessary to maintain nitrogen balance in a population living under the conditions of a developing tropical country. Two different local diets were examined.

Experimental Details

1. Subjects
For the first study, 11 healthy individuals consumed a predominantly animal protein diet (table IA). Eight healthy males took part in the second study of a predominantly vegetable diet (table IB).

2. Study Environment
Location: Universidad del Valle, Colombia. Climate: tropical.

3. Physical Activity
All subjects were students.

4. Diets
For the first study a menu largely made up of animal protein typical of the upper socio-economic class of Colombia was designed, as shown in table 2A. For the second study, the diet was patterned after that in the Cauca Valle region; 80 per cent of this diet is of vegetable origin (table 2B).

TABLE 1. Characteristics of the Subjects

 

1A. Animal Protein Diet

Subject Sex Age
(years)
Weight
(kg)
Height
(cm)
1 M 26 61 167
2 M 21 53 177
3 M 23 62.5 178
4 M 22 90.5 165
5 M 22 68 174
6 M 23 71.5 170
7 M 21 56 175
8 M 22 61 172
9 F 23 53 166
10 F 22 74 175
11 F 22 64 158
X   22.4 64.9 170
S.D.   1.37 10.9 0.061

1B. Vegetable Protein Diet

O.A.01 M 25 55.7 174
A.A.02 M 23 61.0 172
R.E.03 M 22 57.5 163
J.A.04 M 22 64.0 172
J.G.05 M 25 66.5 166
F.P.06 M 24 57.2 170
W.V. 07 M 23 57.7 174
J.D. 08 M 25 63.2 170
X   23.6 60.3 170.1
S. D.   1.3 3.8 3.89

TABLE 2A. Animal Protein Diet

Breakfast: cafe au fait
bread
margarine
marmalade
juice
Mid-morning: Guava candy, sweetened carbonated beverage
Lunch: soup
fried chicken
fried cassava
salad: carrots

cabbage
tomatoes
lettuce
onion
mayonnaise

banana with milk, cream
black coffee, sweetened carbonated beverage

Afternoon: baked plantain, sweetened carbonated beverage
Supper: fried meat
baked potato
salad
fruit
brown sugar water

Take-home snack: Guava candy and sweetened carbonated beverage

5. Experimental Design
For the animal protein study there were four periods; for the vegetable protein study there were seven. Each period consisted of a one-day protein-free diet, a five-day adaptation period, a five-day collection period, and a three-day break.

TABLE 2B. Predominantly Vegetable Protein Diet

Breakfast: orange juice with sugar
fried plantain and margarine
Mid-morning: guava candy and sweetened carbonated beverage
Lunch: sancocho:
typical soup made
of plantain, cassava,
potatoes, meat, oil,
tomatoes, onion,
and parsley
white rice
beans and potatoes
Afternoon: guava candy and sweetened carbonated beverage
Supper: bean soup
beans and potatoes
peaches
sweetened carbonated beverage

Take-home snack: guava candy and sweetened carbonated beverage

6. Nitrogen Balance
The nitrogen content of the diet, urine, and faeces was measured by the micro Kjeldahl technique. Miscellaneous losses were estimated at 5 mg/kg.

Summary of the main results

1. Animal Protein Data
Table 3 shows the nitrogen-balance data. Four of the 11 subjects were classified as behaving atypically and are listed separately in table 3A.

TABLE 3. Nitrogen Balance in Subjects Consuming Protein Mainly of Animal Origin

Subject Nl UNE FNE TNB BV D

Level #1

1 82 85 18 - 26 36 92
3 80 79 20 -24 41.6 90
6 88 70 18 - 5 59.7 93
7 93 91 23 -27 34 88
8 92 76 17 - 6 55 94
9 85 68 26 - 14 56 83
11 80 82 14 -16 42 97.5
X 85 78.7 19.4   46.3 91
S 5.44 8.16 4.0   10.3 4.6

Level #2

1 103 98 21 -15 41 91
2 108 91 21 - 9 45 91
3 104 86 21 - 8 48 91
6 105 105 18 -23 31 94
7 106 88 16 - 3 50 96
8 97 101 20 -29 28 91
9 105 71 22 + 7 64 90
11 98 74 15 -19 48 96
X 103.2 91 19.25   43 92
S 3.8 10.2 2.60   11 2.4

Level #3

3 120 109 20 -14 35 93
3 122 79 21 +16 62 92
6 114 107 10 - 8 39 101
7 114 92 18 - 1 49 94
8 116 86 20 + 5 54 93
9 126 89 16 +17 57 96
11 1 22 96 13 + 7 51 99
X 119 94 16.8   49.5 95.4
S 4.6 11 4.1   9.6 34

Level #4

6 135 99 23 + 8 50 91
7 138 106 28 - 2 43 88
8 136 106 16 + 9 47 97
9 132 93 18 +11 51 95
11 136 72 11 +48 74 100
X 135 96.2 19.2   53 94.2
S 2.19 14.0 6.53   12.4 4.7

Key:

Nl = nitrogen intake
UNE = urinary nitrogen excretion
FNE = faecal nitrogen excretion
TNB = total nitrogen excretion (assuming 5 mg/kg miscellaneous losses)
BV = biological value
D = digestibility

2. Results

  1. Liver function was evaluated by measuring serum transaminase levels (SOOT) at the end of each period; although it was evident that there was a slight increase in the mean level of SGOT with increased protein intake, the mean value of SGOT between groups was not significantly different (ANOVA: p < 0.05).
  2. The regression equation relating the nitrogen intake (Nl) with the urinary nitrogen excretion (UNE) was as follows (values in g/day): UNE = 2.78 + 0.308 Nl; thus, the UNE for 0 intake of protein would be 2.78 9. Assuming a mean weight of 60.7 kg, this corresponds to an obligatory urinary nitrogen excretion of 45.7 mg/kg, which is 7.7 mg/kg higher than that reported by Scrimshaw and others.
  3. There are significant differences in total faecal nitrogen excretion with increasing levels of protein intake (p < 0.001). The regression equation relating faecal nitrogen excretion (FNE) with nitrogen intake (Nl) was: FNE = 0.77 + 0.21 (Nl) (values in g/day); thus, the obligatory nitrogen faecal excretion for zero protein intake was estimated to be 12.4 mg/kg, higher than the figure reported by Young et al. (V.R. Young, M.A. Hussein, and N.S. Scrimshaw, Nature, 218: 568 [1968] ), and just above the 12 mg/kg accepted by the FAD/WHO Committee.
  4. Table 4 shows the data on nitrogen intake, urinary nitrogen excretion, faecal nitrogen excretion, and nitrogen balance expressed in mg/kg/day. The nitrogen balance increases significantly with an increase in nitrogen intake. The regression equation of the nitrogen intake (Nl) expressed in mg/kg/day on the true nitrogen balance (NB) was: NB = -65.84 + 0.50 (Nl).

TABLE 3A. Atypical Subjects

Values in mg/kg/day

Nl UNE FNE TNB BV D

Subject # 2

93 115 30 -57 - 4 80
99 122 32 - 60 - 7 80
121 122 27 -34 +19 87
136 115 26 - 10 +36 89

Subject #4

85 85 12 - 18 +43 100
101 108 21 -33 +22 91
112 107 20 -21 +32.6 92.8
11 5 108 24 - 22 +32 89

Subject # 5

79 92 16 -34 +26 94
96 111 24 -44 +12 87
122 110 30 - 23 +29 85
138 120 20 -10 +35 93

Subject #10

87 78 23 -20 +46 87
94 113 12 -36 +19 100
106 101 27 -27 +30 86
137 114 18 0 +41 96

A close look at the individual data values shows that subject 01 never attained a positive nitrogen balance, and the slope of the regression level relating nitrogen intake with nitrogen balance was 0.35. Although the data for this individual still met the criteria outlined by the WHO-UNU guideline, they were not typical, and it is perhaps not wise to include the data for this subject in the calculations. He had a history of renal stones, and during the study he had a severe attack of renal lithiasis.

TABLE 4. Nitrogen Data for Subjects Consuming the Predominantly Vegetable Protein Diet 1

Subject Level I (0.45)* Level II (0.55) Level III (0.67) Level IV (0.77) Level V (0.86) Level VI (1)

Nitrogen intake

2 68.21 96.21 118.7 120.7 131.5 155.36
3 76.53 89.96 109.8 128.9 137.8 152.0
4 72.11 96.57 106.9 120.1 138.7 161.2
5 69.56 89.98 103.9 127.3 140.6 164.1
6 - - 107.9 129.9 145.4 163.9
7 66.92 88.64 114.3 135.7 148.9 164.9
8 - 83.48 102.3 114.3 - 150.4
X 70.66 90.80 109.1 125.27 140.48 158.8
S.D. 3.79 4.94 5.76 7.25 6.1 6.1

Urinary nitrogen excretion

2 69.2 84.4 88.45 91.71 77.60 99.37
3 76.53 83.7 85.53 95.80 93.10 87.25
4 72.11 67.9 75.23 79.61 78.90 85.10
5 59.6 70.4 81.53 87.17 86.80 109.50
6 - - 77.51 86.83 76.72 95.14
7 75.10 73.5 89.67 80.11 84.13 96.20
8 - 58.7 65.29 84.85 - 92.21
X 70.308 73.1 80.458 86.58 82.87 94.82
S.D. 6.78 9.81 8.57 5.84 6.37 8.19

Faecal nitrogen excretion

2 14.27 22.2 27.0 39.18 47.00 37.4
3 27.30 33.3 26.5 23.0 41.30 44.2
4 37.22 38.3 48.19 46.30 52.37 38.95
5 30.49 36.3 35.84 21.72 45.55 48.09
6 - - 22.7 30.21 53.71 32.00
7 25.32 29.32 35.9 34.10 42.57 43.17
8 - 33.93 42.49 39.49 - 54.57
X 28.92 32.22 34.08 33.428 47.08 42.62
S.D. 5.20 5.77 9.24 9.0 5.0 7.40

Nitrogen balance

2 -14.58 -10.38 + 3.25 -19.19 + 6.92 +18.52
3 -11.44 -27.12 - 2.2 +10.19 + 3.39 +20.53
4 -37.22 - 9.76 -16.51 - 5.81 + 7.41 +37.07
5 -20.53 -16.95 -13.97 +18.41 + 8.33 + 6.57
6 - - + 7.66 +12.25 +15.02 +36.78
7 -33.5 -14.05 -11.25 +21.53 +22.49 +25.54
8 - - 9.16 - 5.5 -10.04 - + 4.68
X -23.45 -14.57 - 5.43 + 5.19 +10.56 +21.39
S.D. (11.41) ( 6.83) ( 8.93) (13.5) ( 6.88) (12.95)
ANOVA   SS DF F P  
Protein intake   8812.4 5 13.3426 0.0000  
    12152.3        

1 Excluding four ''atypical'' subjects.
* All values expressed in mg/kg/day.

The impression of the research team was that throughout the study the subject suffered from a chronic renal infection. This observation and other values considered by the team as errors in collection were deleted. The regression line relating the nitrogen balance (NB) with the nitrogen intake (Nl) after deleting the questionable data was found to be: NB = - 66.7 - 0.52 (Nl).

Conclusions

1. Mean requirement for animal protein was 114 mg N/kg; for vegetable protein it was 128 mg N/kg. (These correspond to 0.71 and 0.80 9 protein, respectively.)

2. With the vegetable protein diet, faecal nitrogen excretion increased as nitrogen intake increased.