Administering labelled water to exclusively breast-fed infants in studies involving stable isotope techniques

Stable isotope techniques using deuterium or 18O are reference methods for assessing total body water (TBW) for body composition. In combination, they provide total energy expenditure and human milk intake in exclusively breast-fed (EBF) infants. These techniques require an oral administration of an accurately quantified dose of labelled water to infants, who often have no prior experience of consuming water. In the present study, 18O labelled water was administered to 47 EBF infants at two time points. Route of administration, duration of dosing and spills were quantified and recorded. Eighty-seven out of 94 (92.6%) dose administrations were successful. In two-thirds of dose administrations,>90% of the prepared dose was consumed. Spills ranged from 0.2% to 57%. Approaches to correct for spills can introduce bias in the calculation of TBW. Minimising and recording all dose spills is an important issue for the accuracy and precision of stable isotope techniques, when applied to EBF infants.