The effect of supplementing a rice diet with lysine, methionine, and threonine on the digestibility coefficient, biological value, and net protein utilization of the proteins and on the retention of nitrogen in children

Abstract

The effect of supplementing a rice diet providing about 1.3-1.4 g protein per kg body weight with lysine, methionine, and threonine individually or together on true digestibility coefficient (DC), biological value (BV), and net protein utilization (NPU) of the proteins has been studied in girls aged 8–9 years. The retention of nitrogen on the rice diet was very low (9.5% of intake in the first series and 8.5% in the second series). The BV and NPU of the proteins of rice diet were 64.1 and 52.9 in the first series and 66.6 and 54.9 in the second series. Supplementation of the rice diet with lysine or methionine or lysine + methionine brought about a significant improvement in N retention (12.6, 12.0, 13.5% of intake) and in the BV (68.3, 66.3, 69.3) and NPU (54.8, 55.7, 55.8). When the rice diet was supplemented with lysine and threonine, a highly significant improvement in the N retention (18.9% of intake) and in the BV (77.4) and NPU (63.4) was observed. Addition of methionine to rice diet containing lysine and threonine resulted in a further improvement in N retention, BV, and NPU of the diets. The net available protein (g/kg body weight) from the different diets were as follows: rice diet, 0.71; rice diet + lysine, 0.76; rice diet + methionine, 0.74; rice diet + lysine + methionine, 0.77; rice diet + lysine + threonine, 0.85; rice diet + lysine + threonine + methionine, 0.91; and skim milk powder diet, 0.96-0.98.