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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 folderEvaluation of the nutritive value of a rice-and-bean-based diet for agricultural migrant workers in Brazil
View the document(introduction...)
View the documentObjective
View the documentExperimental details
View the documentSummary of main results
View the documentConclusions and comments

Experimental details

1. Subjects
Fourteen healthy migrant workers, 17 to 26 years old, were selected. Their characteristics are shown in table 1.

2. Study Environment
All men were admitted to our metabolic unit for the duration of the experiment, and the study was carried out during the summer months (average temperature 23.1 to 24.0 C).

3. Physical Activity
The men were ambulatory; they could walk in the metabolic unit, play card games, and watch television. In addition, they pedalled two to three times per day on a bicycle ergometer, with an energy expenditure of about 850 kcal/day.

TABLE 1. Characteristics of Subjects

Subject no. Age (years) Height (cm) Weight (kg) Mid-arm muscle circumference (% of standard, according to Jelliffe) Albumin (g/dl) Haemoglobin (g/dl)
1 21 172 66.8 98.6 4.6 13.5
2 21 180 70.0 71.5 4.8 14.3
3 22 157 52.0 109.5 4.3 12.8
4 21 179 66.8 92.8 4.4 15.2
5 26 169 60.9 88.9 4.2 15.6
6 20 171 63.0 - 4.2 1 5.6
7 20 172 66.6 92.5 4.6 13.9
8 20 171 59.3 - 4.6 11.7
9 17 159 51.8 - 4.4 13.9
10 24 157 52.6 92.5 4.4 14.2
11 24 173 66.6 107.1 4.4 14.9
12 23 172 63.5 95.2 4.6 1 5.8
13 21 167 61.2 103.1 4.3 15.0
14 22 151 50.6 100.3 4 3 14.7
Mean 21.6 168.3 60.8 95.5 4.4 14.4
S.D. 2.2 81.0 66 10.3 0.2 1.1

4. Duration of the Study
The experiment was divided into one adaptation period of two to three days and one five-day metabolic balance study.

TABLE 2. Intakes of the Rice-and Bean Diet

Food Amount per day (g)
  Range X
Rice 422.4 - 960.0 764.7
Beans 307.2 - 768.0 546.6
Meat 19.2 - 96.0 55.5
Eggs 48.0 17.1 5
Vegetables 28.8 - 192.0 142.1
Coffee and sugar 170.0 - 600.0 508.4

TABLE 3. Protein and Energy Characteristics of the Experimental Diet (Mean Amounts Consumed by 14 Men)

Protein and energy intake Mean S.D.
Total energy (kcal/kg/day) 41.4 6.20
Total protein (g/kg/day) 1.14 0.14
Energy from rice and beans (kcal/day) 1,714 308
Energy from other foods (k cal/day) 789 144
Protein from rice and beans (g/day) 45.6 9.2
Protein from other foods (g/day) 23.6 2.3
Dietary energy density (kcal/g) 1.55 0.08
Rice/bean protein ratio (9/9) 0.72 0.06
Energy/protein ratio (kcal/g) 36.2 2.5

5. Diet
After an initial dietary survey of each individual's food intake, diets were individually prepared. Rice and beans were the main sources of protein, and bread, coffee, small amounts of meat, eggs, and vegetables were also included in the meals. Table 2 shows the range of daily intakes by each of the 14 men. The food was always offered as a bread, with coffee and sugar at breakfast, lunch at noon, a mid-afternoon snack of coffee, sugar, and bread, supper in the early evening, and coffee with sugar at night.

6. Indicators and Meassurements
a. Urine was collected on a timed 24-hour basis. Faeces were collected over the five-day balance period, between administration of carmine and charcoal faecal markers. Urinary creatinine was measured daily (picrate method). Nitrogen in urine, faeces, and food was measured by the Kjeldahl method. Each dietary component was analysed separately, and the nitrogen intake was calculated from the amount of each food consumed. b, Apparent nitrogen balances were calculated from the dietary intakes and urinary and faecal excretions over the five-day period.

Other Studies

A medical examination was carried out on each subject before admission, blood was taken for biochemical profile analyses, and stool and urine samples were obtained for routine laboratory examination.