Factors in the Metabolism of Lactose

The interest pertaining to lactose, because it is the carbohydrate in the diet of the nursling, is magnified by virtue of a number of other more or less related considerations. Half of its molecule is composed of galactose, to which is attributed the importance of serving as a source of certain essential tissue constituents, particularly those of the nervous system. Is it to be concluded that this explains the reason for the presence of this unique carbohydrate in the diet of the developing infant, or are there inherent in the lactose molecule other properties of value ? Once this latter question might have been answered in the affirmative because of the inclusion of glucose in the molecule, but there now seems little doubt that the accompanying glucose facilitates the metabolism of the galactose (Folin and Berglund, 1922; Bodansky, 1923). As one factor involved in this effect, there is to be considered the report of Cori (192%26), that when glucose and galactose were absorbed together, the total amount absorbed was not greater than if either alone was present. In commenting on the results of Folin and Berglund, Benedict and Osterberg (1923) were inclined to feel, “that ‘dilution’ of the galactose with the glucose may be regarded as an adequate explanation of the facts unless experimental evidence is offered which disproves this view.” Bodansky (1923), while admitting that such a factor could not be omitted from consideration, believed t.hat the absorption rate could not be the important factor, because levulose in contradistinction to glucose had such a slight if any effect on galactose hyperglycemia. In this regard, however, it is well to remember that the effect of levulose on galactose absorption has not been quantitatively determined, that levulose has been said to be more slowly absorbed than glucose or galactose (Cori, 1925), and that it is rather hazardous to draw conclusions based on the reducing power of a medley of reducing