The biological values of proteins

Abstract

Thomas introduced the term biological value of protein to express the relative value of different proteins for compensating the daily nitrogenous loss, and defined this as the number of parts of body nitrogen replaceable by 100 parts of the nitrogen of the foodstuff [1909]. He suggested three formulae, differing as regards the treatment of the nitrogen excreted in the faeces, by which to calculate this value from the data of experiments on the nitrogenous exchange. Since that time determinations of the biological values of many proteins have been made by various observers (McCollum [1911, 1914] on the pig; Martin and Robison [1922] on man; Mitchell and his co-workers [1924, 1926, 1927] on the rat; Wagner [1923] on children; and others). The results of these workers show a wide range of variation. For instance, the biological value of the proteins of cow's milk has been variously assessed as 51, 74, 85, 93 and 100 and that of oat protein as 47, 65 and 79.