Quantitative nutritional studies with water-soluble, chemically defined diets. IV. Influence of various carbohydrates on growth, with special reference to d-glucosamine

Abstract

Various chemically defined diets, wherein the sole variable was the source of carbohydrate employed, were offered ad libitum to weanling male rats as 50% solutions in water. Growth responses were best where the sucrose-containing diets were employed, with the d-glucose-, invert sugar-, and d-fructose-containing diets exhibiting both a decreasing order of efficacy and a decreased diet intake. Calculation of the ratio of weight gained to diet intake revealed values of 0.39 – 0.41 for the different diets after some 22 days. Such data indicated that the growth-promoting propensities of the various diets were very nearly the same, with the actual degree of growth attained being dependent upon the diet intake. In addition, a number of diets were prepared which were of identical composition with the exception that various amounts of d-glucosamine were added at the expense of an equal amount of the glucose component. Weanling male rats exhibited a progressively decreasing rate of both growth and diet intake when offered diets of increasing d-glucosamine concentration. The total d-glucosamine intake, at any given time, appeared to reach a limiting value. A plot of weight gain versus diet intake, for the different diets, revealed a remarkably linear relationship and permitted the calculation of base-line diet intake maintenance values, in the absence of growth. The difference between such base-line values, B, and the diet intake, I, then permitted the calculation of the amount of diet, I — B, utilized by the growing animal for increased maintenance needs and growth beyond the initial weight. The ratio of weight gain, G, to I — B, was found to be essentially a constant for the animals on the different diets at any given period after diet administration. It can therefore be assumed that the presence of increasing quantities of d-glucosamine in the diet was not associated with growth inhibition by this carbohydrate, per se, but rather with a decreased diet intake by the animals.