Studies on the protein requirement of Brazilian rural workers ("boias frias") given a rice and bean diet.

The present study was conducted to evaluate the nutritive value of a multiple level rice and bean diet fed to migrant workers. Nine healthy males, 18 to 28 years old were admitted to our metabolic unit for a three period metabolic balance study. The rice and beans based diet was fed at levels to provide 0.4, 0.6 or 0.8 g of protein/kg body weight. Mean energy intake for the three levels of intake and for all subjects was 46.9 +/- 2.9 kcal/kg Bwt/day. Each nitrogen balance period consisted of a) one day on a nitrogen free diet b) five days on an adaptation period, and c) five days on the balance period. "True digestibility', "true nitrogen balance", biologic value, and net protein utilization (NPU) were calculated. Mean protein requirements were estimated by regression analysis of pooled data of balances at different levels of intake. These results showed values of 103.8 mg N/kg Bwt/day. Mean and standard deviation for protein digestibility at each level of intake were 69.2 +/- 17.0, 75.5 +/- 5.3, and 74.9 +/- 10.6% respectively. Mean and standard deviation for NPU were 49.9 +/- 26.3, 55.6 +/- 10.6, and 57.8 +/- 14.4 respectively. The data support the conclusion that a rice and bean diet is a well balanced food combination and can serve as a fairly good source of protein for the adult human.