The Influence of Various Carbohydrates on the Utilization of Low Protein Rations by the White Rat I. Comparison of Sucrose and Cornstarch in 9% Casein Rations

Abstract

The influence of sucrose and that of cornstarch on the utilization by the white rat of low casein rations supplemented with methionine have been determined. Cornstarch supported better growth of rats receiving 9% casein rations than did sucrose. The growth differences were eliminated by increasing either the level of casein or the levels of 5 essential amino acids in the sucrose ration but were unchanged when liver extract was included, when the quantities of the B vitamins were increased or when certain non-essential amino acids were included. The growth of rats fed low casein rations deficient in methionine was also shown to be better when cornstarch was substituted for sucrose as the source of carbohydrate. Various explanations for these observations have been discussed. The growth differences observed cannot be explained satisfactorily by differences in palatability of the rations, by the influence of protein present in cornstarch or by a deficiency of an unknown growth factor. They are apparently due to the availability of greater quantities of certain essential amino acids when sucrose is replaced by cornstarch. It seems improbable that intestinal microorganisms play a significant role in this regard and it is deemed more likely that cornstarch, by reducing the rate of passage of the ration through the gastrointestinal tract, promotes more efficient utilization of low casein rations.