Racial and Sex Differences in 24 Hour Urinary Hydration Markers among Male and Female Emerging Adults: A Pilot Study.

The purpose of this study was to examine 24 h urinary hydration markers in non-Hispanic White (WH) and non-Hispanic Black (BL) males and females. Thirteen males (BL, = 6; WH, = 7) and nineteen females (BL, = 16, WH, = 3) (mean ± SD; age, 20 ± 4 y; height, 169.2 ± 12.2 cm; body mass, 71.3 ± 12.2 kg; body fat, 20.8 ± 9.7%) provided a 24 h urine sample across 7 ( = 13) or 3 ( = 19) consecutive days (148 d total) for assessment of urine volume (U), urine osmolality (U), urine specific gravity (U), and urine color (U). U was significantly lower in BL (0.85 ± 0.43 L) compared to WH college students (2.03 ± 0.70 L) ( < 0.001). Measures of U, U, and U, were significantly greater in BL (716 ± 263 mOsm∙kg, 1.020 ± 0.007, and 4.2 ± 1.4, respectively) compared to WH college students (473 ± 194 mOsm∙kg, 1.013 ± 0.006, 3.0 ± 1.2, and respectively) ( < 0.05). Differences in 24 h urinary hydration measures were not significantly different between males and females ( > 0.05) or between the interaction of sex and race/ethnicity ( > 0.05). Non-Hispanic Black men and women were inadequately hydrated compared to their non-Hispanic White counterparts. Our findings suggest that development of targeted strategies to improve habitual fluid intake and potentially overall health are needed.