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close this bookProtein-Energy Requirements of Developing Countries: Evaluation of New Data (UNU, 1981, 268 p.)
close this folderProtein-energy requirements-children
close this folderEnergy requirements of pre-school children and effects of varying energy intakes on protein metabolism
View the document(introduction...)
View the documentObjectives
View the documentExperimental details
View the documentSummary of main results
View the documentConclusions and comments

Experimental details

1. Subjects

  1. Six boys of mixed Maya Indian and Caucasian descent (Lading).
  2. Chronological age: 30 8 months (range: 22 to 40 ). Height-age: 17 5 months (range: 15 to 25).
  3. All had been treated for severe, oedematous protein-energy malnutrition (kwashiorkor and marasmic kwashiorkor). They had recovered fully at least one month before beginning the studies, based on clinical, anthropometric, and biochemical criteria (plasma proteins, non-essential/essential amino acid ratio, haematological indices, urinary creatinine excretion, and creatinine-height index [CHI]).
  4. Weight: 11.93 0.95 kg (range: 10.85 to 13.25). Height: 84.4 3.5 cm (range: 78.2 to 88.6).
  5. Weight-for height, percentage of expected: 104 4% (range: 89 to 109).
  6. All children were healthy throughout the study, except for occasional minor illnesses, such as upper respiratory infections of viral aetiology, that were treated symptomatically. In a few instances a child had fever for one to three days. If that happened immediately before or at the time scheduled for nitrogen-balance studies, the balance was postponed until seven days after the fever had subsided. Energy expenditure was not measured during days when a child had fever. f. Intestinal parasites: Two children (nos. 387 and 390) had mild infestation with Trichuris trichiura. Two others 1388, 394) had Giardia lamb/ia, and one of them (394) also had mild ascariasis. All were asymptomatic and none was treated before or during the study.

2. Study Environment
INCAP's Clinical Centre in Guatemala City, 1,500 metres above sea level. Temperature 18 to 24 C. Relative humidity 40 to 60 per cent, except during rainy days. All children spent two to four hours each day in outdoor playing facilities, except on rainy days.

3. Physical Activity
The children were encouraged to be about as active as those living in a free environment, rather than leading the sedentary life usually observed in children who live in an institution. This was accomplished by encouraging them to participate throughout the day in various games that required walking, running, and climbing ramps and stairs. They were never forced to participate, and the games never exhausted them.

4. Duration of the Study
Five children were studied for 120 days, 40 days with each of three levels of dietary energy. The sixth child was studied for 160 days with four levels of dietary energy, as described below.

5. Diet
a. The diets were based exclusively on vegetables, with 95 per cent more of the protein derived from black beans (Phaseolus vulgaris) and corn. The diets were designed to provide 1.75 9 protein/kg/day. The proportion of black beans to corn protein was 42:58. Three different levels of energy intake were used: initially about 100 kcal/kg/day and after 40 day intervals about 92 and 83 kcal/kg/day.

The 100 kcal level was that used in previous experiments when the requirement for corn-and-bean protein was established. This energy intake was excessive for several children who became obese during those experiments. Only one child (KG) ate a higher energy-dense diet after he failed to gain the expected weight with the initial intake of 100 kcal/kg/day and lost weight with 92 kcal/kg/day. His energy intake was then raised to 120 kcal/kg/day, and at 40-day intervals it was lowered to 110 and 100 kcal/kg/day. It should be pointed out that while this child was recovering from protein-energy malnutrition before participating in the present study he required a diet with 150 kcal/kg/day for a longer period than was needed by the other children for recuperation. The changes in dietary energy were made by adding more or less vegetable oil to the black bean preparations, as shown in table 1.

b. As the components of the diet were those used locally in Central American rural and low-income urban homes, no multivitamins and mineral supplements were added, except for supplementary iron and vitamin A provided with sugar fortified with NaFeEDTA (13 mg of iron per 100 9 of sugar), and retinol palmitate (15 micrograms of vitamin A in 1 9 of sugar).

c. Table 2 shows the proportions of energy provided by fat, protein, and carbohydrate. The diet provided 0.54 9 crude fibre/kg body weight/day.

d. The foods were prepared and cooked in ways similar to those followed in Guatemalan homes, except that with the higher levels of energy intakes more oil was used than is customary in low-income homes. Table 3 shows the foods served in every meal. The same menus and amounts of food were served each day throughout the study, adjusted for each child's average weekly body weight.

6. Indicators and Measurements
a. Nitrogen and energy balance: Every 20 days, urine and faeces were collected for 96 hours and analysed to determine their nitrogen and energy contents. The same was done with an aliquot of the diets. Nitrogen was determined by an automated method using alkaline phenol-hypochlorite-nitroprussiate (Berthellot reaction) after a Kjeldahl digestion; food and faecal aliquots were homogenized and solubilized with H2O2-H2SO4 before digestion. "True" nitrogen balance was calculated by subtracting urinary, faecal, and insensible losses from the amount of nitrogen ingested. It was assumed that the insensible losses were 5 mg/kg/day.

Energy in diets and faeces was measured by bomb calorimetry using benzoic acid standards. Energy balance was calculated by subtracting from the dietary energy intake (measured by bomb calorimetry): the faecal energy (measured by bomb calorimetry); urinary energy losses (estimated as 5 kcal/g urinary nitrogen); sweat (estimated as 0.1 kcal/kg/day, based on 8 kcal/g sweat nitrogen; and the total energy expenditure, as described below.

b. Absorption: Twenty mg N/kg/day were used as the obligatory faecal losses to calculate "true" nitrogen digestibility.

TABLE 1. Ingredients and Amounts of Foods Eaten


Amount (g)

Protein (g)

Fat (g)

Energy (keel)

Amount eaten per kg/day

Black bean paste (pur        

16.6 g/kg

Black bean flour










Vegetable oil













Water enough to reach













Corn tamale        

15.1 g/kg

Lime-treated corn flour

















Corn gruel (atole)        

50 g/kg

Lime-treated corn flour




















Lemonade —(10 g sugar/100 g = 40 kcal/100 g)   25 g/kg
Banana —(1 g protein and 106 kcal/100 g)   5 g/kg
Cooked carrots —(0.2 g protein end 31 kcal/100 g)** approx. 5 g/kg
Cooked squash —10.5 g protein and 20 kcal/100 g)** approx. 2 g/kg
Boiled potatoes —(1.1 g protein and 42 kcal/100 g)** approx. 1.3 kg/kg
Cooked spinach —(2 g protein and 17 kcal/100 g)** approx. 1.7 g/kg

* 11.8 per cent oil added to provide a total of about 100 kcal/kg/day. Figures in parentheses correspond to diets that provided about 92 or 83 kcal/kg/day.
** Only two of these vegetables were served each day

TABLE 2. Nutrient Contents of the Diet as Energy Sources*


Theoretical dietary energy levels (kcal/kg/day)

% Energy from:






Total fats

27.0 (23)+

24.8 (21)

22.5 (18)

15.5 (10)

5.9 (0)













* Based on Atwater factors and proximal analysis of beans, corn, tamale, corn gruel, and lemonade, and on food composition tables for banana and other vegetables.
** Diets with 120 and 100 kcal/kg/day were consumed only by child E,G. (no, 387).
+ In parentheses: percentage of energy derived from vegetable oil added to black beans.

c Total energy expenditure: Physical activity and energy expenditure were quantified by monitoring the children's heart rate throughout the day and calculating energy expenditure from individual determinations of heart rate and oxygen consumption. The heart-rateoxygen-consumption relationship was determined in each child at 20-day intervals. Total daily energy expenditure was calculated from each child's heart rate and his corresponding heart-rate-energy expenditure relationship from 5 a.m. to 8 p.m. ( 15 hours), and from his basal energy expenditure from 8 p.m. to 5 a.m. of the following day (9 hours).

Basal energy expenditure was measured by indirect calorimetry with an oxygen diaferometer at two day intervals, each time on two separate occasions not more than three days apart; the lower of the two results was considered as basal. Basal conditions were defined as after a minimum of eight hours of sleep and ten hours of fast. Measurements were done while the child was sleeping, sometimes after oral administration of chloral hydrate (4 mg/kg). Energy expenditure was calculated by indirect calorimetry, assuming a respiratory quotient of 0.82.

d. Growth and body composition: The children were weighed naked before breakfast every morning. Anthropometric measurements were taken at 14-day intervals. Basal oxygen consumption was measured on 2 consecutive days at approximately 20-day intervals. Urinary creatinine excretion was determined at 20-day intervals when the nitrogen-balance determinations were carried out.

e. Other determinations: Initially and at two-day intervals, packed blood cell volume and total plasma proteins were determined.

f. The experimental design is summarized in table 4.

TABLE 3. Menu Used in the Study

Breakfast: corn gruel (corn flour + sugar + cinnamon + calcium) *
tamale (corn flour + salt + calcium)
beans (black bean flour + salt + vegetable oil)
Mid-morning snack: banana
lemonade (lemon juice & sugar)
Lunch: corn gruel
cooked carrots or spinach
Mid-afternoon snack: banana
Dinner: corn gruel
mashed potatoes or squash

* Ingredients are shown in parentheses.

TABLE 4. Summary of Experimental Design and Schedule

Experimental days                              
0 4 8 12 16 20 24   28   32 36 40
  44 48 52 56 60 64   68   72 76 80
  84 88 92 96 100 104   108   112 116 120
Procedures A, B BEE, HR       A   NE, B   A BEE, HR       A,B,NE

Diet: Protein: 1.75 g/kg/day throughout the study. Energy: initially 100/kcal/kg/day and decreased to 92 and 84 kcal/kg/day on days 41 and 81, respectively (only exception: child E,G., see text).
A: Anthropometric measurements: height; perimeters of arm and leg; tricipital, subscapular, and abdominal subcutaneous skin-fold thicknesses. Weight was measured every day.
B: Packed red blood cell volume, plasma proteins, and urinary creatinine.
NE: Nitrogen and energy balance.
HR: Heart-rate-energy-expenditure relationship. Heart rate continuously monitored 5 days before and 5 days afterwards.
BEE: Basal energy expenditure.

TABLE 5. Mean Daily Intakes of Dietary Protein and Energy During the 4-Day Balance Periods


Protein (g/kg)

Energy (kcal/kg)*








1.73 0.03 (6) ***


99 (2)

92 (2)

83 (2)


1.75 0.06 (8)

118 (2)

106 (2)

100 (3)

97 (1)



1.69 0.04 (6)


99 (2)

89 (2)

78 (2)


1.75 0.01 (6)


95 (2)

84 (2)

76 (2)


1.79 0.01 (6)


102 (2)

94 (2)

86 (2)


1.63 0.04 (6)


100 (2)

92 (2)

84 (2)

Average 1.73 0.06 (38) 118 (2) 106 (2) 99 3 (13) 91 4 (11) 81 4 (10)
Mean net energy intakes **** 106 96 90 82 71

* Gross intakes, i.e., bomb calorimetry values not corrected for faecal energy excretion.
** Theoretical levels of energy intakes.
*** Mean standard deviation (number of balance period).
**** Net intakes = gros sintekes - faecal losses (bomb calorimetry).