Twenty-four-hour urine osmolality as a physiological index of adequate water intake.

Erica T Perrier,Alexis Klein,Mariacristina Vecchio,Inmaculada Buendia-Jimenez,Ivan Tack,Lawrence E Armstrong

doi:10.1155/2015/231063

Erica T Perrier, Alexis Klein + Show 4 more

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https://doi.org/10.1155/2015/231063

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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 (UOsm) 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 UOsm 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.

Highlights

Hydration is a dynamic balance between water intake and loss, and body water balance is maintained through both behavioral and physiological responses
The first and second approaches suggest that a 24 hour urine osmolality (UOsm) of less than or equal to 500 mOsm⋅kg−1 represents an intake that is adequate to compensate for daily losses and ensure a urinary output sufficient to reduce the risk of urolithiasis and decline in renal function
U500 was supported by the third approach, which revealed that 24 h urine osmolality of >500 mOsm⋅kg−1 was associated with elevated plasma arginine vasopressin (AVP) concentrations suggestive of antidiuretic effort

Summary

Introduction

Hydration is a dynamic balance between water intake and loss, and body water balance is maintained through both behavioral and physiological responses. Adequate intakes representing population median consumption have been reported [1, 2]; the intake necessary to maintain optimal hydration from a physiological and health standpoint is still unknown. This is in part because water is essential to sustain life and normal physiological functions, research quantifying the dose-response effect of water on health is very limited. Accurately measuring water intake is difficult, especially over long periods of time, and relatively little research has focused on average adults with mostly sedentary lifestyles and occupations [3]

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