[Effect of animal protein supplementation and energy on the protein quality of diets based on rice and beans in adult males].

Four short nitrogen balance index studies were carried out in adult subjects to evaluate the biological quality of a mixture based on rice and beans, and also to measure the effect of animal protein and/or energy supplementation on the nutritive value of the mixture. In the first study, rice supplied 60% and beans, 40% of the protein's diet, which was administered at an energy level of 45.5 kcal/kg/day of metabolizable energy. A regression coefficient of 0.76 +/- 0.11 was found between ingested nitrogen and nitrogen balance, and a value for nitrogen maintenance of 96.2 +/- 13.7 mg/kg/day. When this same diet was administered in the second study at a 51.2 kcal/kg/day of metabolizable energy, the regression coefficient was 0.80 +/- 0.13, and that of nitrogen for maintenance, 90.1 +/- 8.7 mg/kg/day, without differences being significant (P less than 0.05) for any of the two measures. In the third study, 10% of the mixture's protein was substituted by milk protein, and given at a level of 45.2 kcal/kg/day of metabolizable energy. In this case, the regression coefficient found was 0.96 +/- 0.08, and that of nitrogen for maintenance, 78.6 +/- 10.2 mg/kg/day. These values do differ significantly (P less than 0.05) from those found in the two previous studies. When the diet of the third study was administered to the same subjects at a level of 48.9 kcal/kg/day of metabolizable energy, the regression coefficient of the equation was 0.86 +/- 0.17, and that for maintenance nitrogen, 82.4 +/- 10.2 mg/kg/day. These values are statistically equal to those found in the third study and do differ significantly from those of the first two studies. Information indicates that the supplementary effect of protein and milk occurs mainly at the digestive level. It is therefore concluded that when rice and beans are consumed jointly, in the adequate proportions, they constitute an excellent-quality food for adult humans.