|Protein-Energy Requirements of Developing Countries: Evaluation of New Data (UNU, 1981, 268 p.)|
|Research papers: Protein requirements-adults, standard protocols|
|Evaluation of the nutritive value of a rice-and-bean-based diet for agricultural migrant workers in Brazil|
Summary of main results
Conclusions and comments
J.E. Dutra de Oliveira, Helio Vannucchi, and Rosa M.F. Duarta B.
Division of Nutrition, Metabolic Unit, University Hospital, Ribeirao Preto, Sao Paulo, Brazil
This study was carried out to investigate the composition and nutritive value of the diet, largely based on rice and beans, habitually consumed by agricultural migrant workers in Brazil.
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)|
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)|
|Rice||422.4 - 960.0||764.7|
|Beans||307.2 - 768.0||546.6|
|Meat||19.2 - 96.0||55.5|
|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|
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.
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.
Table 3 shows that rice and beans were the main source of energy and protein in the diet. This table also shows the total daily energy and protein intakes, the contributions made by rice and beans, and the dietary energy density.
The results of apparent nitrogen balance and apparent digestibility of the diet are shown in table 4.
Body weight and urinary creatinine excretion did not change during the five-day period.
The rice-and-bean diet satisfied the men's energy requirements, at least under the conditions of this short-term metabolic study.
TABLE 4. Nitrogen Balance and Apparent Digestibility of Dietary Nitrogen(Means of Five Days)
|Subject||Nitrogen intake (mg/kg/day)||Total urinary nitrogen (mg/kg/day)||Faecal nitrogen (mg/kg/day)||Apparent nitrogen balance (mg/kg/day)||"True" nitrogen balance* (mg/kg/day)||Apparent digestibility (%)|
|3||176.2||140.4||46.2||- 10.5||- 15.5||73.8|
|4||170.8||138.5||38.3||- 6.0||- 11.0||77.6|
|8||204.7||146.0||63.4||- 4.7||- 9.7||69.0|
|10||168.6||128.1||44.6||- 4.2||- 9.2||67.5|
* Assuming miscellaneous losses of 5 mg/kg/day.
Based on these results, the energy and protein needs of these workers could be met if sufficient amounts of the rice-and bean diet were available. This is not always the case at the community level, since preliminary surveys showed that there were inadequate intakes of energy, protein, and other nutrients.