title: Twenty-four-hour urine osmolality as a physiological index of adequate water intake.
abstract: While associations exist between water, hydration, and disease risk, research quantifying the dose-response effect of water on health is limited. Thus, the water intake necessary to maintain optimal hydration from a physiological and health standpoint remains unclear. The aim of this analysis was to derive a 24 h urine osmolality (U(Osm)) threshold that would provide an index of "optimal hydration," sufficient to compensate water losses and also be biologically significant relative to the risk of disease. Ninety-five adults (31.5 ± 4.3 years, 23.2 ± 2.7 kg·m(-2)) collected 24 h urine, provided morning blood samples, and completed food and fluid intake diaries over 3 consecutive weekdays. A U(Osm) threshold was derived using 3 approaches, taking into account European dietary reference values for water; total fluid intake, and urine volumes associated with reduced risk for lithiasis and chronic kidney disease and plasma vasopressin concentration. The aggregate of these approaches suggest that a 24 h urine osmolality ≤500 mOsm·kg(-1) may be a simple indicator of optimal hydration, representing a total daily fluid intake adequate to compensate for daily losses, ensure urinary output sufficient to reduce the risk of urolithiasis and renal function decline, and avoid elevated plasma vasopressin concentrations mediating the increased antidiuretic effort.
authors: Danone Research, 91767 Palaiseau, France.
authors: Erica T
authors: ET
authors: Perrier
authors: Danone Research, 91767 Palaiseau, France.
authors: Inmaculada
authors: I
authors: Buendia-Jimenez
authors: Danone Research, 91767 Palaiseau, France.
authors: Mariacristina
authors: M
authors: Vecchio
authors: Department of Kinesiology, Human Performance Laboratory, University of Connecticut, Storrs, CT 06269, USA.
authors: Lawrence E
authors: LE
authors: Armstrong
authors: Service des Explorations Fonctionnelles Physiologiques et INSERM 1048, Equipe 12, CHU de Rangueil, 31432 Toulouse, France.
authors: Ivan
authors: I
authors: Tack
authors: Danone Research, 91767 Palaiseau, France.
authors: Alexis
authors: A
authors: Klein
mesh_terms: D000328:Adult; D004326:Drinking; D005260:Female; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D064167:Recommended Dietary Allowances; D016482:Urinalysis / Q000379:methods; D014556:Urine / Q000737:chemistry*; D014882:Water-Electrolyte Balance