Low-cost measurement of body composition with 18O-enriched water.

Total body water (TBW) and body composition are crucial for the estimation of nutritional status in many clinical circumstances. While the measurement of TBW with 18O-enriched water is technically easier than with 2H2O, the cost of 10% 18O-enriched water can be regarded as prohibitive. The aim of this study was to prove that less enriched (i.e. 2%) and cheaper (about 25 ECU per dose per subject, i.e. $30) 18O water can be used to measure TBW. In the 41 subjects studied, isotopic equilibrium was achieved 4 hours after the isotope was administered. Plateau enrichments in urine, saliva, and plasma samples did not differ significantly between 5 and 8 hours after the dose. TBW measurements in 8 of these subjects showed no significant differences, regardless of whether 2% or 10% water was used. We conclude that accurate estimates of TBW and body composition can be obtained with low-cost, 2% 18O-enriched water.