Urine color for assessment of dehydration among college men students in Hebei, China - a cross-sectional study

Background and Objectives: To examine the association between quantified urine color and urine osmolality, and its validity in distinguishing hydration status among college men in Hebei, China. Methods and Study Design: Sixty-eight college men aged 18 similar to 25 years completed a cross-sectional study. All participants were asked to complete a 24-h fluid intake record to estimate fluid intake from beverages after anthropometric measurements. The foods eaten by participants were weighed to assess fluid intake from foods. All urine samples for the day were collected by participants to determine urine osmolality and urine color by chromatogram spectrophotometry (in accord with the Commission Internationale de l'Eclarige (CIE) notation L*a*b*). Results: A total 413 urine samples from 68 participants were collected and 151 (36.6%) samples indicated dehydration according to urine osmolality. The dehydrated group versus hydrated group had a smaller urine color L* (94.88 vs 98.06) and a* (-2.39 vs -1.91), bigger b* (30.41 vs 15.15), and higher osmolality (958 mOsm/kg vs 486 mOsm/kg). Urine color and osmolality were closely correlated, especially for b* (0.86, p<0.0001). The percentage variance in urine osmolality (R-2) explained by a partial least squares (PLS) model was 79%. Urine color b* contributed most substantially to the PLS model, with variable importance for projection of 1.35. The cutoff for b* for adequate hydration was 17.78 (area under the curve=0.899). Conclusions: Differences in urine color between dehydrated and hydrated status related to urine osmolality. Urine color quantification is a reliable method to assess hydration status among young Chinese men.