Effects of Three Oral Nutritional Supplements on Human Hydration Indices.

Urine color (U_col) as a hydration assessment tool provides practicality, ease of use, and correlates moderately to strongly with urine specific gravity (U_sg) and urine osmolality (U_osm). Indicative of daily fluid turnover, along with solute and urochrome excretion in 24-hr samples, U_col may also reflect dietary composition. Thus, the purpose of this investigation was to determine the efficacy of U_col as a hydration status biomarker after nutritional supplementation with beetroot (880 mg), vitamin C (1000 mg), and riboflavin (200 mg). Twenty males (Mean ± SD\ age, 21 ± 2 y; body mass, 82.12 ± 15.58 kg; height, 1.77 ± 0.06 m) consumed a standardized breakfast and collected all urine voids on one control day (CON) and 1 day after consuming a standardized breakfast and a randomized and double-blinded supplement (SUP) over 3 weeks. Participants replicated exercise and diet for one day before CON, and throughout CON and SUP. U^col, U_sg, U_osm, and urine volume were measured in all 24-hr samples, and U_col and U_sg were measured in all single samples. U_col was a significant predictor of single sample U_sg after all supplements (p < .05). Interestingly, 24-hr U_col was not a significant predictor of 24-h U_sg and U_osm after riboflavin supplementation (p = .20, p = .21). Further, there was a significant difference between CON and SUP 24-h U_col only after riboflavin supplementation (p < .05). In conclusion, this investigation suggests that users of the UCC (urine color chart) should consider riboflavin supplementation when classifying hydration status and use a combination of urinary biomarkers (e.g., U_sg and U_col), both acutely and over 24 hr. [ABSTRACT FROM AUTHOR]