Nutritional Improvement of white Polished Rice by the Addition of Lysine and Threonine

Abstract

Highly significant improvement of natural rice protein as it existed in polished rice was accomplished by the addition of two essential amino acids, lysine and threonine. This combination produced a growth response in white rats three times that obtained with an unsupplemented rice diet. Neither lysine nor threonine, nor any other essential amino acid, added to rice individually produced better growth than rice alone. Rice plus lysine and threonine supplemented with all the other essential amino acids individually and with all the possible combinations of pairs was not further improved. Supplementation with many of the possible combinations of three and 4 of the remaining essential amino acids was without favorable effect. When rice was supplemented with all the deficient essential amino acids simultaneously, growth was improved considerably more than by supplements of only lysine and threonine but was still not optimum. These results indicate that lysine and threonine are the most deficient essential amino acids in rice and that they are about equally limiting for rat growth. A threefold excess of arginine or methionine when added to rice completely supplemented with all other essential amino acids produced a significant growth depression. An excess of the other essential amino acids individually was without effect.