PURPOSE: The prevalence of hypohydrated children has been reported as 54.5%, with males more hypohydrated. Hydration status and fluid drinking habits of college-aged students are unclear. Also, it is uncertain if sex differences continue into young adulthood. Therefore, the purpose of this project is to analyze hydration status in college-aged students and to identify sex differences. METHODS: First morning body mass, urine and thirst levels were collected in 21 males (age = 21 ± 1 y, body mass = 78.7 ± 14.6 kg) and 22 females (age = 20 ± 1 y, body mass = 65.4 ± 12.6 kg) over 10 days. Subjects were euhydrated (urine specific gravity [USG]: <1.020) for the first 3 days, followed by free-living fluid consumption the remaining 7. First morning percent body mass Loss (%BML), thirst, USG, urine osmolality (Uosmo) and urine color (Ucolor) were analyzed between the 3 day baseline average and 7 day free-living average. 2 x 2 (sex x time) repeated measures ANOVA with post-hoc paired t-tests were used, with alpha set at 0.05. A Venn diagram introduced by Cheuvront et al determined daily hydration status during free-living condition. Dehydration parameters were defined as %BML >1%, Ucolor > 5 and thirst >4. Two markers present indicated fluid intake was considered “likely inadequate,” and three markers indicated “very likely inadequate.” RESULTS: Time difference (Baseline to Free-Living Mean ± SD, p-value) between the euhydrated baseline and free-living days for USG (1.013 ± 0.005 to 1.018 ± 0.004, 0.001), Uosmo (405 ± 114 to 660 ± 179, 0.001) and Ucolor (3 ± 1 to 5 ± 1, 0.001) was found, but not for %BML (-0.07 ± 0.18 to -0.33 ± 0.81, 0.108) or thirst (5 ± 1 to 5.5 ± 1-0.2, 0.55). No sex differences for any hydration measure were found. Based on the Venn criteria, regardless of sex, fluid intake was likely inadequate 38.9%, and very likely inadequate 6.1% of the time. CONCLUSIONS: For this sample, regardless of sex, there were differences for all hydration markers except %BML and thirst when comparing the euhydrated baseline to 7 days of free-living. However, there were no differences in hydration markers based on sex. Finally, fluid needs were considered likely inadequate 38.9%, and very likely inadequate 6.1% of the time. This is important to consider as inadequate hydration state may negatively impact overall health and mental acuity, regardless of sex.
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