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Body composition, energy expenditure and physical activity

Evaluation of Uosm:Posm ratio as a hydration biomarker in free-living, healthy young women

European Journal of Clinical Nutrition volume 67, pages 934–938 (2013)Cite this article

Subjects

Abstract

Background/objectives:

Urinary and plasma indices are utilized to assess whole-body water balance in healthy adults, whereas the urine-to-plasma osmolality ratio (Uosm:Posm) rarely is. To explore the efficacy of Uosm:Posm as a hydration biomarker, diet records of 120 college women were analyzed (beverage water+food water=total fluid intake (TFI); 5 days) to identify habitual high-volume (HIGH) and low-volume (LOW) drinkers.

Subjects/methods:

The experimental protocol first involved two ad libitum baseline days for HIGH (TFI, 3.21 l per 24 h; n=14) and LOW (TFI, 1.64 l per 24 h; n=14). During a controlled intervention (days 3–6), mineral water was the only beverage; HIGH consumed less than baseline (TFI, 2.00 l per 24 h), and LOW consumed more than baseline (TFI, 3.50 l per 24 h). During ad libitum recovery (day 7), TFI were 3.17 and 1.71 l per 24 h for HIGH and LOW, respectively. Duplicate Uosm (24 h collection) and Posm (morning) samples were analyzed on all days via freezing point depression osmometry.

Results:

In the evaluation of relative water excess (Uosm:Posm<1.0), 11/13 values occurred for HIGH on days 1, 2 and 7; for LOW, 28/29 occurred on intervention days 3–6. Chi-squared analysis indicated that the treatment and Uosm:Posm were significantly associated (χ21:0.001=23.5, P<0.001). Statistical regression analyses detected a strong, significant relationship between renal free-water clearance (FWC) and Uosm:Posm (r2=0.86, P<0.00001); this was not true for FWC and Posm (r2=0.00, P=0.40) because Posm values were stable across 7 days.

Conclusions:

These findings support the use of Uosm:Posm as a hydration biomarker.

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Acknowledgements

This work was funded by Danone Research, France.

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Authors and Affiliations

  1. Department of Kinesiology, Human Performance Laboratory, University of Connecticut, Storrs, CT, USA

    L E Armstrong, E C Johnson, C X Munoz, A L McKenzie, D J Casa & C M Maresh

  2. Danone Research, Palaiseau, France

    L Le Bellego & A Klein

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  1. L E Armstrong
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  2. E C Johnson
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  3. C X Munoz
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  4. L Le Bellego
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  6. A L McKenzie
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  7. D J Casa
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Correspondence to L E Armstrong.

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Competing interests

Professor Armstrong has received compensation as a consultant to ILSI NA and to Danone Research, Palaiseau France; he serves as a Scientific Advisory Board and Expert Working Group member for the Hydration for Health Initiative of Danone Research. Laurent Le Bellego, PhD and Alexis Klein, PhD are employed as researchers, by the grant sponsor Danone Research. Evan C Johnson, Amy L McKenzie, Colleen X Muñoz, Douglas Casa and Carl Maresh declare no conflict of interest.

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Armstrong, L., Johnson, E., Munoz, C. et al. Evaluation of Uosm:Posm ratio as a hydration biomarker in free-living, healthy young women. Eur J Clin Nutr 67, 934–938 (2013). https://doi.org/10.1038/ejcn.2013.79

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