[Nitrogen balance in adults and experimental study in rats fed with rice, beans and manioc flour supplemented with...

Rice, beans and manioc flour are foods eaten daily in Northeast Brazil. Manioc flour is a source of energy, having a low protein content. There has been a great interest to supplement manioc flour with proteins. The present study was planned to show the nutritive value of a basic diet including rice, beans, manioc flour and other local foods, supplemented with different sources of proteins. The experiment was carried out in humans and rats. The supplements used were casein (Ca), isolated soy protein (PS) and a dry residue of a soymilk preparation (RSLS). Through nitrogen balance studies in adults it was shown that the diets with casein or isolated soy protein had a good absorption and retention of nitrogen. The addition of the soymilk residue resulted in a poor acceptance of the experimental diet; negative nitrogen retention was observed in the three persons who accepted the food and completed the balances studies. The same diets offered to humans, with the same protein supplements, were fed to rats. The nutritive value measured in the animals were similar, in all diets with all supplements, including the one with the dry residue of soymilk. The present results call the attention to the problems of transfering animal results to humans. It was also discussed the possibility of adding casein or isolated soy protein as an eventual protein supplement to manioc flour for human feeding.