RESUMO
Information is provided on the nitrogen intake for nitrogen equilibrium in young human adults fed a cassava/bean diet and a plantain/bean diet. Ten individuals participating in each study ingested levels of 0, 0.2, 0.4 and 0.6 g protein/kg/day at a constant energy level (45 kcal/kg/day), using the short-term nitrogen balance method with multiple intakes. Even with intakes of 105.7 and 117.4 mg N/kg/day for the cassava/bean and plantain/bean diets, the experimental subjects did not reach a positive balance. The protein digestibility of the diets was low, as had been confirmed previously for beans alone: 55.7% for the cassava/bean study and 50.4% for plantains/beans. The average quantity of nitrogen intake required to reach nitrogen equilibrium for the cassava/bean diet was 114.3 mg N/kg/day and for the plantain/bean diet, 111.9 mg N/kg/day. In the case of the cassava/bean diet, the variability was 81.3 to 172.4, and for plantain/beans, 83.6 to 219.3 mg/kg/day. In four of the five individuals who participated in both studies, the nitrogen intake required to reach nitrogen equilibrium was greater when fed the diet based on plantain/beans than when fed the cassava/beans diet. These data support the assertion that the protein requirement is not a simple figure. Individual variability is so great that, as has been suggested, it is necessary to add two standard deviations to the average figure to cover 97.5% of the population. The results of this investigation support the need to increase protein digestibility and protein quality of beans, since this is a food of major importance for large population segments in the developing countries.