Department of Kinesiology, Human Performance Laboratory, University of Connecticut, Storrs, CT 06269-1110, USA.
Eur J Clin Nutr. 2013 Mar;67(3):249-53. doi: 10.1038/ejcn.2012.214. Epub 2013 Feb 6.
BACKGROUND/OBJECTIVES: This investigation evaluated 12 hydration biomarkers, to determine which represent 24-h whole-body water balance (that is, measured as water retention or clearance (WR-C) by the kidneys).
SUBJECTS/METHODS: Healthy males (n=59; body mass, 75.1±7.9 kg; height, 178±6 cm; age, 22±3 years; body mass index, 23.9±2.4 kg/m(2)) met with a registered dietitian each morning (days 1-11) to optimize completeness and accuracy of food and fluid records, then went about ordinary daily activities. These men visited the laboratory for blood samples and collected all urine produced on days 1, 3, 6, 9 and 12. The reference standard (WR-C) was calculated using 24-h urine volume, 24-h urine osmolality, and serum osmolality (single morning venous sample).
Statistical regression analyses indicated that, among the 12 hydration biomarkers, only 24-h urine osmolality (r(2)=0.60, P<0.0001) and 24-h urine specific gravity (r(2)=0.52, P<0.0001) strongly predicted WR-C. The 24-h fluid intake, 24-h body mass change, 24-h urine color and 24-h urine volume were weak (P>0.05) predictors of WR-C, similar to serum osmolality and other single measurements (range of r(2) values, 0.19-0.0001).
These observations of healthy, active young men demonstrate that WR-C is strongly related to the 24-h concentration of urine, which in turn reflects the excretion of total solids in the diet. Although morning urine assessments provided information about a single time point, 24-h urine osmolality and 24-h urine specific gravity were the best predictors of 24-h body water balance.
背景/目的：本研究评估了 12 种水合生物标志物，以确定哪些标志物代表 24 小时全身水平衡（即通过肾脏测量的水保留或清除（WR-C））。
受试者/方法：健康男性（n=59；体重 75.1±7.9kg；身高 178±6cm；年龄 22±3 岁；体重指数 23.9±2.4kg/m2）每天早上与注册营养师会面（第 1-11 天），以优化食物和液体记录的完整性和准确性，然后进行日常活动。这些男性每天到实验室采集血液样本，并在第 1、3、6、9 和 12 天采集所有尿液。参考标准（WR-C）通过 24 小时尿液量、24 小时尿液渗透压和血清渗透压（单次清晨静脉样本）计算得出。
统计回归分析表明，在 12 种水合生物标志物中，只有 24 小时尿液渗透压（r2=0.60，P<0.0001）和 24 小时尿液比重（r2=0.52，P<0.0001）强烈预测 WR-C。24 小时液体摄入量、24 小时体重变化、24 小时尿液颜色和 24 小时尿液量是 WR-C 的弱（P>0.05）预测因子，与血清渗透压和其他单次测量相似（r2 值范围，0.19-0.0001）。
这些对健康、活跃的年轻男性的观察结果表明，WR-C 与尿液 24 小时浓度密切相关，而尿液 24 小时浓度又反映了饮食中总固体的排泄。尽管晨尿评估提供了单一时间点的信息，但 24 小时尿液渗透压和 24 小时尿液比重是 24 小时身体水平衡的最佳预测因子。
