Urinary markers of hydration during 3-day water restriction and graded rehydration

• Published in: European journal of nutrition 2020-08, Vol.59 (5), p.2171-2181
• Main Authors: Johnson, Evan C., Huffman, Ainsley E., Yoder, Hillary, Dolci, Alberto, Perrier, Erica T., Larson-Meyer, D. Enette, Armstrong, Lawrence E.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Color; Fluid intake; Hydration; Nutrition; Original Contribution; Rehydration; Urine; Water intake
• ISSN: 1436-6207; 1436-6215
• DOI: 10.1007/s00394-019-02065-7

Purpose This investigation had three purposes: (a) to evaluate changes in hydration biomarkers in response to a graded rehydration intervention (GRHI) following 3 days of water restriction (WR), (b) assess within-day variation in urine concentrations, and (c) quantify the volume of fluid needed to return to euhydration as demonstrated by change in U col . Methods 115 adult males and females were observed during 1 week of habitual fluid intake, 3 days of fluid restriction (1000 mL day −1 ), and a fourth day in which the sample was randomized into five different GRHI groups: no additional water, CON; additional 500 mL, G +0.50 ; additional 1000 mL, G +1.00 ; additional 1500 mL, G +1.50 ; additional 2250 mL, G +2.25 . All urine was collected on 1 day of the baseline week, during the final 2 days of the WR, and during the day of GRHI, and evaluated for urine osmolality, color, and specific gravity. Results Following the GRHI, only G +1.50 and G +2.25 resulted in all urinary values being significantly different from CON. The mean volume of water increase was significantly greater for those whose U col changed from > 4 to