COMPARISON OF METHODS FOR ESTIMATING FECAL CARBOHYDRATE EXCRETION IN PREMATURE-INFANTS

Our previous studies have suggested that there is minimal fecal excret ion of carbohydrate-derived energy in premature infants fed lactose or glucose-polymer as the source of carbohydrate. In these studies, carb ohydrate energy excretion was equated with the non-nitrogenous, nonfat energy. Although these studies provided consistent results, this meth odological approach cannot distinguish actual excretion of dietary car bohydrate from carbohydrate in the form of large molecular compounds d erived from infant or bacterial cells (which in fact comprise approxim ately 90% of the measured value). Therefore, in this study we compared the absorption of carbohydrate energy to the fractional absorption of C-13 derived from [D-1-C-13]-lactose in 10 premature infants 30-32 we eks gestational age fed either a commercial premature infant formula c ontaining a mixture of carbohydrates (50% lactose: 50% glucose polymer ) or the same formula in which lactose was the sole carbohydrate. The two methods provided comparable estimates of carbohydrate absorption ( 96 and 94%, respectively), although there were significant discrepanci es in two infants. These studies provide evidence of external validity for the two methods.