Supplementation of Cereal Proteins with Amino Acids

Abstract

As a further test of amino acid supplementation of a protein, using the amino acid levels of the FAO reference protein as a guide, children were fed diets in which rolled oats, supplemented with potentially limiting amino acids, were the sole protein source. The series began and ended with isonitrogenous, isocaloric periods in which milk served as the protein source and basal periods of the unsupplemented oat diet were interspersed between each test period. Each diet was fed for 3 successive 3-day periods. At intakes of 2 g of protein/kg, no significant effect on nitrogen retention was observed with additions to 308 mg/g N of lysine, to 296 of methionine or both together. At a level of 222 mg/g N of threonine alone or in combination, the increase was significant and the nitrogen retention only slightly below that with milk. At 1.5 g of protein/kg, some increase in retention was observed with either lysine alone or methionine alone to these levels. Threonine alone was not tested. The combination of either lysine and methionine or all 3 amino acids gave a further increase in retention. A tendency for a higher retention in a basal period following an experimental one in which methionine had been one of the supplementary amino acids was noted. This was interpreted as due to an adverse effect of methionine supplementation at the level of this amino acid in the FAO reference protein, as previously observed with the methionine supplementation of corn diets.