Supplementation of Cereal Proteins with Amino Acids

Abstract

In the first of two experiments using the nitrogen balance technique in children, it was shown that the addition of lysine to a basal wheat diet brings about a marked increase in nitrogen retention. Nitrogen retention values as high as or higher than those obtained with isonitrogenous feeding of milk were obtained by feeding a wheat basal diet supplemented with a mixture containing the FAO levels of lysine, tryptophan, methionine, isoleucine, valine, and threonine. About 90% of the response, however, was found to be due to the combined lysine and tryptophan supplement. In the second experiment, the effect of protein level of intake on the minimal lysine supplement to be added to wheat flour was studied in 6 children. Maximal retention of nitrogen was obtained with the addition of 162 to 194 mg lysine/gm of nitrogen to a basal diet fed at a rate of 2 and 3 gm of protein/kg of body weight per day, respectively. Within the range of the protein fed, the amount of lysine per gram of nitrogen that must be added did not vary significantly with protein intake. The results demonstrate once again that it is necessary in amino acid supplementation studies to consider not only the adequacy of the amount of each amino acid, when others are present in optimal quantities, but also the effect of excesses of some amino acids. Maximal responses is obtained only when a correction is made in the amount of the most limiting amino acid in such a way as to improve the balance or proportion among the other essential amino acids. This is a fundamental characteristic of the FAO or any other amino acid reference pattern.