For healthy children up to 15 years of age, no data exist regarding water turnover as directly measured using stable isotope techniques. Water turnover was measured in 171 healthy children (88 girls, 83 boys, age: 6 weeks-15 years) whilst living in their normal environment. Water turnover was calculated from the equilibrium of 2H2O concentration reached in the urine 2-3 h after an oral test load of 2 ml 2H2O/kg and the subsequent elimination rate of 2H2O. Daily water turnover decreased from 160 ml/kg (3 months), 100 ml/kg (12 months), 65 ml/kg (3 years) to 40 ml/kg at 15 years of age. Fluid intake was then calculated by subtracting the estimated metabolic water production from water turnover and this data was compared with recommended values. Our calculation of spontaneous daily fluid intake for these healthy children is within the recommended range during the 1st year of life, whereas for older children the recommendations exceed the spontaneous intake by a factor of 1.2-2.
Body composition of 165 healthy children was measured using the well-established method of deuterium oxide (2HzO) dilution. After distribution of an oral load of 2.0 ml 'H,O/kg body weight body water was estimated from the 2H,0 concentration in urine. Lean body mass was then calculated from body water using previously published age dependent ratios of the water content of the lean body mass. Fat mass was calculated as the difference of body weight and lean body mass. A good correlation was found between body water and body weight. Linear regression revealed TBW = 0,589 BW + 0.728 (r = 0.99). Body water, lean body mass and fat mass were found to change with age. The fat content of the body increases during the first six months of life. It then decreases until four to five years then rising again until 15 years of age.
65 MoellerS (spn. by N. Henchkowilz*), Universily Childrens I4ospitals of CH-3010 Bern' and D-7400 Tibingenf. Recommendations of fluid requirenlents of he;~l~hy children aiven bv oedialric textbooks have been tlieoreticallv derived. but not
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