Hydration, Fluid Intake, and Related Urine Biomarkers among Male College Students in Cangzhou, China: A Cross-Sectional Study—Applications for Assessing Fluid Intake and Adequate Water Intake

Abstract

The objectives of this study were to assess the associations between fluid intake and urine biomarkers and to determine daily total fluid intake for assessing hydration status for male college students. A total of 68 male college students aged 18–25 years recruited from Cangzhou, China completed a 7-day cross-sectional study. From day 1 to day 7; all subjects were asked to complete a self-administered 7-day 24-h fluid intake record. The foods eaten by subjects were weighed and 24-h urine was collected for three consecutive days on the last three consecutive days. On the sixth day, urine osmolality, specific gravity (USG), pH, and concentrations of potassium, sodium, and chloride was determined. Subjects were divided into optimal hydration, middle hydration, and hypohydration groups according to their 24-h urine osmolality. Strong relationships were found between daily total fluid intake and 24-h urine biomarkers, especially for 24-h urine volume (r = 0.76; p < 0.0001) and osmolality (r = 0.76; p < 0.0001). The percentage of the variances in daily total fluid intake (R2) explained by PLS (partial least squares) model with seven urinary biomarkers was 68.9%; two urine biomarkers—24-h urine volume and osmolality—were identified as possible key predictors. The daily total fluid intake for assessing optimal hydration was 2582 mL, while the daily total fluid intake for assessing hypohydration was 2502 mL. Differences in fluid intake and urine biomarkers were found among male college students with different hydration status. A strong relationship existed between urine biomarkers and fluid intake. A PLS model identified that key variables for assessing daily total fluid intake were 24-h urine volume and osmolality. It was feasibility to use total fluid intake to judge hydration status.

Fluid intake in urban China: results of the 2016 Liq.In 7 national cross-sectional surveys

“…For adults, the TFI in current survey differed by only approximately 100 mL/day compared with the fluid intake survey of adults in four Chinese cities (1584 vs 1488, mL/day) in 2010 [20]. In a survey with the Liq.In 7 record specifically conducted in young adults (aged 18–25 years) in China in 2015, TFI was 1342 mL/day and less than the adults in this survey [37]. In a systematic review including 273 studies in different countries (only one Asia survey in China was included; the majority being USA and European surveys), it was concluded that TFI varied between 0.6 and 3.5 mL/day in the general population and 0.6–1.8 mL/day amongst children, 0.8–2.0 mL/day amongst adolescents, and 0.8–3.4 mL/day amongst adults [38].…”

“…In a systematic review including 273 studies in different countries (only one Asia survey in China was included; the majority being USA and European surveys), it was concluded that TFI varied between 0.6 and 3.5 mL/day in the general population and 0.6–1.8 mL/day amongst children, 0.8–2.0 mL/day amongst adolescents, and 0.8–3.4 mL/day amongst adults [38]. Another survey using the Liq.In 7 record in 2015 also indicated that only approximately a quarter of the Chinese young adults met the recommendation [37]. Harmonized cross-sectional fluid specific surveys performed in 15 countries showed that a relatively high proportion of subjects (38%) failed to meet the recommendation on fluid intake and this proportion significantly varied among countries [39].…”

Drinking patterns and hydration biomarkers among young adults with different levels of habitual total drinking fluids intake in Baoding, Hebei Province, China: a cross-sectional study

“…While among elderly aged ≥60 years from NHANES 2011-2014, 29.6% and 33.3% of women and men had Sosm (osmolality of serum) levels indicative of impending dehydration, with 10.2% and 12.6% of women and men had Sosm levels indicative of dehydration [20]. In China, there was merely one study exploring hydration status among male young adults, which showed that only 35.3% of them were in optimal hydration status [21]. Research showed that the participants with low total drinking fluids excreted significantly less volume of urine than those with high total drinking fluids over each 24 h period [22].…”

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

“…Because the GRHI took place over a single 24 h period, it is possible that a second day of increased water intake within many of the intervention groups may have allowed those participants to return to U col < 4. Although from a different geographical population, the finding that free-living individuals with habitual TWI > 2500 mL day −1 were associated with optimal hydration [39] supports the theory that a longer duration of G +1.50 or G +2.25 GRHI would have been successful in returning a greater proportion to more desirable urine concentrations.…”