The Comparative Nutritive Values of Glucose, Fructose, Sucrose and Lactose When Incorporated in a Complete Diet

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Abstract
When sucrose, fructose and lactose constitute 60 to 70% of the diets of growing rats, these diets being otherwise complete, the digestibility of the organic nutrients of the diets, as compared with that of diets containing equal concentrations of glucose, is distinctly impaired, the impairment being least for sucrose, intermediate for fructose, but by far the greatest for lactose. The slight impairment in the digestibility of the organic nutrients in the sucrose ration did not affect the rate of gain of the rats nor the composition of the gains in such nutrients. On the fructose ration, the rate of growth was definitely slower as was the rate of deposition of protein. But on the lactose ration, the greatly impaired digestibility induced markedly slower rates of growth and rates of deposition of all organic nutrients. The fecal wastage of calcium was not increased by fructose and lactose as compared with glucose, and the metabolic utilization of calcium was definitely increased by sucrose, fructose and lactose as compared in each case with glucose. Lactose, in addition, definitely promoted the utilization of phosphorus in metabolism as compared with glucose. It may be concluded, therefore, that the differences in the metabolic disposal of the various sugars studied and their different physiological effects, observed when the sugars are administered alone, largely disappear when they are fed as components of a complete diet. Administered in a complete diet, the nutritive values of the sugars appear to be very much the same except for differential effects on the digestibility of the organic nutrients of the rations. Sucrose, fructose and lactose do seem to favor the utilization of calcium more than does glucose, while lactose promotes also the utilization of phosphorus. But these effects too may be the result of intestinal conditions more favorable to the absorption of calcium and of phosphorus prevailing on diets containing 60 to 70% of sucrose, fructose and lactose, as compared with those conditions prevailing on a predominantly glucose diet.