Relationships Between WUT (Body Weight, Urine Color, and Thirst Level) Criteria and Urine Indices of Hydration Status

Abstract

Background: A Venn diagram consisting of percentage body mass loss, urine color, and thirst perception (weight, urine, thirst [WUT]) has been suggested as a practical method to assess hydration status. However, no study to date has examined relationships between WUT and urine hydration indices. Thus, the purpose of this study was to investigate relationships between urine specific gravity, urine osmolality, and the WUT criteria. Hypothesis: Urine specific gravity and urine osmolality indicate hypohydration when the WUT criteria demonstrate hypohydration (≥2 markers). Study Design: Laboratory cohort study. Level of Evidence: Level 3. Methods: A total of 22 women (mean ± SD; age, 20 ± 1 years; mass, 65.4 ± 12.6 kg) and 21 men (age, 21 ± 1 years; body mass, 78.7 ± 14.6 kg) participated in this study. First morning body mass, urine color, urine specific gravity, urine osmolality, and thirst level were collected for 10 consecutive days in a free-living situation. Body mass loss >1%, urine color >5, and thirst level ≥5 were used as the dehydration thresholds. The number of markers that indicated dehydration levels were counted and categorized into either 3, 2, 1, or 0 WUT markers that indicated dehydration. One-way analysis of variance with Tukey pairwise comparisons was used to assess the differences in urine specific gravity and urine osmolality between the different number of WUT markers. Results: Urine specific gravity in 3 WUT markers (mean ± SD [effect size], 1.021 ± 0.007 [0.57]; P = 0.025) and 2 WUT markers (1.019 ± 0.010 [0.31]; P = 0.026) was significantly higher than 1 WUT marker (1.016 ± 0.009). Urine mosmolality in 2 WUT markers (705 ± 253 mOsmol [0.43]; P = 0.018) was significantly higher than 1 WUT (597 ± 253 mOsmol). Meeting at least 2 WUT markers resulted in sensitivities of 0.652 (2 WUT criteria met) and 0.933 (3 WUT criteria met) to detect urine osmolality >700 mOsmol. Conclusion: These results suggest that when 3 WUT markers are met, urine specific gravity and urine osmolality were greater than euhydration cutoff points. The WUT criterion is a useful tool to use in field settings to assess hydration status when first morning urine sample was used. Clinical Relevance: Athletes, coaches, sports scientists, and medical professionals can use WUT criteria to monitor dehydration with reduced cost and time.

Origins of thirstiness sensation and current food solutions

“…(2021) and Sekiguchi et al. (2022). But when researchers want to study thirst evolution, thirstiness can be assessed over a period of time within the same session.…”

“…This allows different types of thirst results to be obtained, depending on what is being targeted. For example, overall thirst has been assessed over 8 and 10 days, but always in the morning, by Anderson et al (2021) and Sekiguchi et al (2022). But when researchers want to study thirst evolution, thirstiness can be assessed over a period of time within the same session.…”

“…” (Allida et al., 2021; Anderson et al., 2021). The questions asked reflect the difficulty in self‐assessing thirstiness perception, and that the thirstiness sensation is not usually asked about as a single parameter but is associated with other parameters such as refreshing, saliva stimulating (van Belzen et al., 2017), dry mouth (Armstrong et al., 2020; Oztas & Oztas, 2022; Zhang et al., 2022), or urine osmolality (Sekiguchi et al., 2022). It has also been shown that the VAS is equally valid whether it is on paper or in electronic format (Delgado et al., 2018).…”

“…The quantification of urine osmolality assessed in duplicate by a freezing point depression osmometer has been found to be a valid parameter for assessing hydration status (Armstrong et al., 2014). Also, the osmolality and color of urine seem to be robust methods related to thirst and hydration status (Anderson et al., 2021; Sekiguchi et al., 2022). Recently, it has also been proposed that urine color is the parameter that most rapidly detects changes in hydration status (Edwards & Buono, 2022).…”

The weight, urine colour and thirst Venn diagram is an accurate tool compared with urinary and blood markers for hydration assessment at morning and afternoon timepoints in euhydrated and free-living individuals

“…When all three markers are met, then an individual is 'very likely dehydrated' (1,3,8) . Sekiguchi et al (2022) validated the WUT Venn diagram in relationship to urinary hydration indices (urine specific gravity (USG) and U OSM ); however, this tool has not been validated with haematologic indices, which may provide greater utility for clinical hydration assessment in athletes compared with urinary markers (2,9) . In addition, the relationship between the WUT Venn diagram and other hydration markers has only been assessed using first-morning measurements.…”