Abstract
Background: Although water is the most abundant and most vital of all human nutrients, hydration is among the most ignored aspects of human nutrition. Many different solutes are eliminated by the kidneys in the urine flow, potentially contributing to the osmotic charge of this body fluid and acting as determinants of the urinary osmolality [Uosm]. Objectives: To measure urine osmolality concurrently with urea, uric acid, calcium, magnesium, potassium, sodium and inorganic phosphorus in a 24 h sample and to determine the patterns of their mutual interactions towards assessing the primary determinants of Uosm. Methods: Seventy-eight children from 2 to 7 years old, 40 girls and 38 boys, with median age of 57 mo underwent 24 h urine collections, with an aliquot separated for measuring urine osmolality by freezing-point-depression osmometry and solute concentrations by various analytical chemistry techniques. Spearman correlations and multiple regression models were run to assess interactions. Results: Backward-elimination multiple-regression models found that the urinary concentrations of inorganic phosphorus, urea, sodium, potassium and magnesium explained 95.1% of the variance in Uosm among the seven analytes quantified; calcium and uric acid made negligible contribution. Conclusion: The analyses allowed us to confirm the determinant roles of urea and the principal electrolytes, sodium and potassium, for urine osmolality and to appreciate coordination in the collateral collinear associations with other excreted solutes.
Highlights
The analyses allowed us to confirm the determinant roles of urea and the principal electrolytes, sodium and potassium, for urine osmolality and to appreciate coordination in the collateral collinear associations with other excreted solutes
[Uosm] was among the lowest of those reported across the pediatric literature [3], signifying a relatively superior hydration status
The study was conducted in the Western Highlands of Guatemala in the province of Quetzaltenango, located 220 km from Guatemala City and 2357 m above the sea level, with a land area of 1,943 km2 and 24 municipalities [6]; the Secretariat for Beneficial Works of the First Lady [SOSEP] named three different daycare centers to our study, one located in La Esperanza, a semi-urban location (Center A); another located really close to the city, La Puerta del Llano, but classified as marginal-urban, (Center B); and the last one, and in the most rural setting, San Martín Sacatepéquez, (Center C)
Summary
Water is the most abundant and most vital of all human nutrients [1,2], hydration is among the most ignored aspects of human nutrition This is especially true for juvenile populations, for which there are limited data based on quantitative urine collections [3]. Water is the most abundant and most vital of all human nutrients, hydration is among the most ignored aspects of human nutrition. Many different solutes are eliminated by the kidneys in the urine flow, potentially contributing to the osmotic charge of this body fluid and acting as determinants of the urinary osmolality [Uosm]
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