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TABLE 2. Laboratory Evaluation of the Nutritional Status of "Boias-frias"

TABLE 3. Creatinine Excretion of the "Boias-frias" (g/day)

TABLE 4. Intake of Rice and Bean Diet, Amount per Day (g/kg)

Metabolic balances, digestibility, biological value, and NPU were calculated from dietary intake and urinary and faecal excretion over the five-day periods. Integumental nitrogen losses were estimated to be 5 mg/kg (1), and the metabolic urinary and faecal nitrogen to be 2.58 and 0.60 mg N/kg, respectively (2). Mean protein requirement and protein allowance were estimated by the individual regression line method described by Rand et al. (3).

TABLE 5. Relationship Between Protein and Calories from Rice and Beans in the Three Diets (Mean ± SD)

TABLE 6. Energy Intake (Kcal/kg bwliday) from Rice and Bean Diet for Rural Migrant Workers.

A medical check-up was given to each patient before admission. Blood was always taken for biochemical profile analysis. and stools and urine were collected for routine laboratory examination.

Results

The average intake of each of the ingredients offered to the subjects at each protein level of the diets is shown in table 4. Rice and beans were always the main source of protein, as shown in table 5. The mean caloric density of diets was similar at all three levels of intake. Average daily intakes of energy were 2,750 ± 230 kcal daily during the study (table 5), or 46.9 ± 2.9 kcal/kg (table 6).

Results of the crude nitrogen balance, digestibility, NPU, and biological value of the rice and bean diet are shown in table 7.

The estimation of the mean protein requirement is 107.1 mg N/kg bwt/day, and the protein allowance is 137.6 mg N/kg bwt/day, as shown in table 8.

TABLE 7. True Nitrogen Balance. True Digestibility, NPU and Biologic Value in the Three Diets of Rice and Beans (Averages of Five Days)

TABLE 8. Linear Regression of N Balance Response (mgN/kg/day), of Brazilian Rural Workers with a Rice and Bean Diet (Individual Data)

y = N balance (mg/kg/day)
x = N intake (mg/kg/day)
Intercept (y = 0) = N intake for the maintenance of N equilibrium (mg/kg/day)

Discussion

The average daily faecal and urinary nitrogen excretion increased with higher protein intake (table 7).

The true digestibility increased when the intake went from 0.4 to 0.6 g/kg bwt, but stayed at about the same level when the intake increased to 0.8 g/kg bwt (table 7).

The data on biological value and NPU showed a pattern similar to that of true digestibility: an increase when the protein intake went from 0.4 to 0 6, but practically no change at levels from 0.6 to 0.8 9 of protein per kg of body weight (table 7).

Here again, faecal excretion of nitrogen appears to be the most important factor, since values were higher during the 0.6 and 0.8 g/kg levels of intake. Nitrogen retention increased with the higher protein intake, but the increase was less when the 0.6 level is compared with the 0.8. The caloric intake was kept at about the same level throughout the study and did not influence the results.

Using individual response lines, the estimated mean requirement is 66.9 9 protein with a standard deviation of 9.5 (table 8). These results are lower than the ones found by Calloway and Kretsch in their study of adults fed a diet based on beans, corn, and rice (4). They confirm our previous results in children and adults fed rice and bean diets (5, 6), showing the possibility of reaching nitrogen equilibrium at a lower nitrogen intake.

References

1. D.H. Calloway, A.C.F. Odell, and S. Margen, "Sweat and Miscellaneous Nitrogen Losses in Human Balance Studies," J. Nutr., 101: 775 (19711.

2. V.R. Young, Y.S.M. Taylor, W.M. Rand, and N.S. Scrimshaw, "Protein Requirements of Man: Efficiency of Egg Protein Utilization at Maintenance and Submaintenance Levels in Young Men," J. Nutr., 103: 1164 (1974).

3. W.M. Rand, N.S. Scrimshaw, and V.R. Young, "Determination of Protein Allowances in Human Adults from Nitrogen Balance Data," Am. J. Chin. Nutr., 30: 1129 (1977).

4. D.H. Calloway and M.J. Kretsch, "Protein and Energy Utilization in Men Given a Rural Guatemalan Diet and Egg Formulas with and without Added Oat and Bran," Am. J. Clin. Nutr., 31: 1118 (1978).

5. H. Vannucchi, R.M.F. Duarte, and J.E. Dutra de Oliveira, "Nutritive Value of a Rice and Beans-Based Diet for Agricultural Migrant Workers in Southern Brazil," Nutr. Rep. Internat., 24: 129 (1981).

6. J. E. Santos, J.M. Howe, F.A.M . Duarte, and J.E. Dutra de Oliveira, " Relationships between the Nutritional Efficacy of a Rice and Bean Diet and Energy Intake in Preschool Children," Am. J. Clin. Nutr.. 32: 1541 (1979).

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