Urine Hydration Research Articles

NMR Precision Metabolomics: Dynamic Peak Sum Thresholding and Navigators for Highly Standardized and Reproducible Metabolite Profiling of Clinical Urine Samples.

Metabolomics, especially urine-based studies, offers incredible promise for the discovery and development of clinically impactful biomarkers. However, due to the unique challenges of urine, a highly precise and reproducible workflow for NMR-based urine metabolomics is lacking. Using 1D and 2D non-uniform sampled (NUS) 1H-13C NMR spectroscopy, we systematically explored how changes in hydration or specific gravity (SG) and pH can impact biomarker discovery. Further, we examined additional sources of error in metabolomics studies and identified Navigator molecules that could monitor for those biases. Adjustment of SG to 1.002-1.02 coupled with a dynamic sum-based peak thresholding eliminates false positives associated with urine hydration and reduces variation in chemical shift. We identified Navigator molecules that can effectively monitor for inconsistencies in sample processing, SG, protein contamination, and pH. The workflow described provides quality assurance and quality control tools to generate high-quality urine metabolomics data, which is the first step in biomarker discovery.

Differences in urine creatinine and osmolality between black and white Americans after accounting for age, moisture intake, urine volume, and socioeconomic status.

Urine osmolality is used throughout research to determine hydration levels. Prior studies have found black individuals to have elevated urine creatinine and osmolality, but it remains unclear which factors explain these findings. This cross-sectional, observational study sought to understand the relationship of self-reported race to urine creatinine and urine osmolality after accounting for age, socioeconomic status, and fluid intake. Data from 1,386 participants of the 2009-2012 National Health and Nutrition Examination Survey were utilized. Age, poverty-to-income ratio (PIR), urine flow rate (UFR), fluid intake, estimated lean body mass (LBM), urine creatinine, and urine osmolality were measured. In a sex-specific manner, black and white participants were matched on age, dietary moisture, UFR, and PIR. Urine creatinine was greater in black men (171 mg/dL) than white men (150 mg/dL) and greater in black women (147 mg/dL) than white women (108 mg/dL) (p < .001). Similarly, urine osmolality was greater in black women than white women (723 vs. 656 mOsm/kg, p = .001), but no difference was observed between white and black men (737 vs. 731 mOsm/kg, p = .417). Estimated LBM was greater in black men (61.8 kg) and women (45.5 kg) than in white men (58.9 kg) and women (42.2 kg) (p≤.001). The strongest correlate of urine osmolality in all race-sex groups was urine creatinine (Spearman ρ = .68-.75). These results affirm that individuals identifying as black produce higher urine creatinine concentrations and, in women, higher urine osmolality after matching for age, fluid intake, and socioeconomic status. The findings suggest caution when comparing urine hydration markers between racial groups.

Storing urine samples with moisture preserves urine hydration marker stability up to 21 days

To assess hydration status, hydration markers [urine color, osmolality, and urine-specific gravity (USG)] are used. Urine color, osmolality, and USG have shown to be stable for 7, 7, and 3days, respectively, at 4°C. However, refrigeration could produce a dry environment which enhances evaporation and potentially affects urine hydration markers. To examine the effect of duration and moisture on urine markers with refrigeration. 24 participants provided urine samples between 9 and 10 AM. Urine color, osmolality, and USG were analyzed within 2h (baseline). Then, each urine sample was divided into two urine cups and placed in a storage container with (moisture condition) and without (no moisture condition) water bath at 3°C. Hydration markers were analyzed at day 1(D1), D2, D7, D10, D14, and D21. A two-way ANOVA (time x condition) and repeated-measures ANOVA on time were performed to examine differences. No significant (p > 0.05) condition x time effect was observed for urine color (p = 0.363), urine osmolality (p = 0.358), and USG (p = 0.248). When urine samples were stored in moisture condition, urine color (p = 0.126) and osmolality (p = 0.053) were stable until D21, while USG was stable until D2 (p = 0.394). When assessing hydration status, it appears that the urine color and osmolality were stable for 21days, while USG was stable for 2days when stored with moisture at 3°C. Our results provide guidelines for practitioners regarding urine storage duration and conditions when urine cannot be analyzed immediately.

Hydration monitoring and rehydration guidance system for athletes based on urine color’s L*a*b* parameters

Maintaining proper hydration is essential for athletes to sustain optimal performance and preserve their physical health. Existing studies have confirmed that urine color is one of the effective indicators for the subjective evaluation of athletes' hydration through the urine color chart. However, the use of urine color charts to evaluate hydration is easily affected by the test environment, urine container and subjective feeling. At present, there are few hydration monitoring instruments based on quantitative analysis of urine color. In recent years, the L*a*b* color model has been widely used in the objective quantitative analysis of color. The L* value represents the luminance change from black to white, the a* value represents the chromaticity change from green to red, and the b* value represents the chromaticity change from blue to yellow. Our previous research has confirmed that the urine color b ∗ value is an effective new indicator to evaluate the hydration of athletes. The research team developed a urine hydration monitoring and rehydration guidance system based on the urine color's L*a*b* parameters via wireless network technology and digital image technology. The hardware structure of the system is composed of a cuvette, a standard light source, a camera, an image collector, a host system, and a touch screen system. The system software is composed of functional modules, such as user information, image acquisition, image processing, and image recognition. The system operation process includes starting the system, filling in basic information, putting the sample, testing the sample, local data review, local data upload, and cloud data review. The system exhibits stable performance, a friendly operation interface, and simple and fast testing. It can objectively and accurately evaluate the hydration of athletes and provide personalized rehydration guidance. The system offers a new method for solving practical problems in sports training, and it has broad application prospects.

Relationships Between WUT (Body Weight, Urine Color, and Thirst Level) Criteria and Urine Indices of Hydration Status.

A Venn diagram consisting of percentage body mass loss, urine color, and thirst perception (weight, urine, thirst [WUT]) has been suggested as a practical method to assess hydration status. However, no study to date has examined relationships between WUT and urine hydration indices. Thus, the purpose of this study was to investigate relationships between urine specific gravity, urine osmolality, and the WUT criteria. Urine specific gravity and urine osmolality indicate hypohydration when the WUT criteria demonstrate hypohydration (≥2 markers). Laboratory cohort study. Level 3. A total of 22 women (mean ± SD; age, 20 ± 1 years; mass, 65.4 ± 12.6 kg) and 21 men (age, 21 ± 1 years; body mass, 78.7 ± 14.6 kg) participated in this study. First morning body mass, urine color, urine specific gravity, urine osmolality, and thirst level were collected for 10 consecutive days in a free-living situation. Body mass loss >1%, urine color >5, and thirst level ≥5 were used as the dehydration thresholds. The number of markers that indicated dehydration levels were counted and categorized into either 3, 2, 1, or 0 WUT markers that indicated dehydration. One-way analysis of variance with Tukey pairwise comparisons was used to assess the differences in urine specific gravity and urine osmolality between the different number of WUT markers. Urine specific gravity in 3 WUT markers (mean ± SD [effect size], 1.021 ± 0.007 [0.57]; P = 0.025) and 2 WUT markers (1.019 ± 0.010 [0.31]; P = 0.026) was significantly higher than 1 WUT marker (1.016 ± 0.009). Urine mosmolality in 2 WUT markers (705 ± 253 mOsmol [0.43]; P = 0.018) was significantly higher than 1 WUT (597 ± 253 mOsmol). Meeting at 3 WUT resulted in specificity of 0.956 and at 0 WUT resulted in sensitivity of 0.937 for urine osmolality>700mOsm. These results suggest that when 3 WUT markers are met, urine specific gravity and urine osmolality indicated hypohydration and 0 WUT represents a high likelihood of euhydration. 1 and 2 WUT values are indeterminate of hydration status. The WUT criterion is a useful tool to use in field settings to assess hydration status when first morning urine sample was used. Athletes, coaches, sports scientists, and medical professionals can use WUT criteria to monitor dehydration with reduced cost and time.

Comparison Of Different METHODS For Urine Hydration Assessment

Several instruments and techniques to assess hydration via urine exist; but which is used for evaluation depends on diagnostic accuracy, reliability, cost, and convenience. Urine specific gravity assessed via refractometry is a common field technique for urine assessment; however, previous comparisons of different refractometers have provided contradicting reports of bias. PURPOSE: To identify agreement between different refractometers (manual and digital) to measure urine specific gravity, as well as assess the diagnostic accuracy of urine specific gravity compared to osmolality. METHODS: Free-living participants (n = 39, 27 males, 12 females, age 25 ± 5 y, ht 1.76 ± 0.09 m, wt 81.1 ± 15.2 kg, BMI 26.2 ± 4.1) volunteered to provide a spot urine sample. Each sample was evaluated in duplicate with an osmometer (Osmo1 Single-Sample Micro-Osmometer), manual refractometer (Atago MASTER-SUR/Nα), and digital refractometer (Atago PAL-10S). Bland-Altman analysis was performed to assess agreement between manual and digital refractometers. Diagnostic accuracy of refractometers to identify concentrated samples (≥1.025) was conducted using receiver operating characteristic curves with osmolality (≥850 mOsm/kg) as the standard. RESULTS: Samples evaluated with the digital (1.018 ± 0.008) and manual (1.018 ± 0.007) refractometers were highly correlated (r = 0.998, P < 0.001). Bland-Altman analysis demonstrated high agreement between manual and digital refractometers (mean difference: 0.0002 ± 0.0004). Compared with osmolality, the digital refractometer identified concentrated samples with an area-under-the curve (AUC) of 0.86, sensitivity of 0.71, and specificity of 1.00. The manual refractometer identified concentrated samples with an AUC of 0.89, sensitivity of 0.79, and specificity of 1.00. CONLUSION: This study demonstrated a high agreement between manual and digital refractometers, suggesting either instrument would be acceptable for use. When compared to osmolality, both instruments provided excellent specificity for identifying diluted samples, but moderate sensitivity for identifying concentrated samples.

Characterizing Dietary and Physical Activity Patterns in Relation to Hydration Among Pre-Adolescent Children

Abstract Objectives The aim of this study was to characterize food and fluid consumption as well as and physical activity patterns in children in relation to ad libitum hydration. Methods Child participants aged 9–11 years (N = 55, 28 females) reported beverage consumption with a 7-day fluid diary. Overall diet was reported using a 7-day diet record and analyses were run using the Nutritional Data System for Research (NDSR). Physical activity was assessed with hip worn accelerometers (Actigraph wGT3x+, Pensacola, FL) over 7 days and aerobic fitness was measured with a VO2 max test. Body composition was assessed with dual energy x-ray absorptiometry (DXA). Urine was collected over a 24hr period and was analyzed separately with a refractometer and freezing point depression for specific gravity (USG) and osmolality (UOsm), respectively. Results Children reported ad libitum consumption of 1645 ± 856 mL of total fluid per day, which was comprised of 37% plain water and 12% milk. The remaining 51% was composed of juice, carbonated, sports, fruit, and caffeinated beverages. Mean 24 h UOsm was 780 ± 250 mOsm/kg and USG was 1.019 ± 0.007. Activity data showed participants spent 52 minutes of MVPA/day. Partial correlations, adjusting for VO2 max, % body fat, sex, energy intake, and accelerometer wear time per day, revealed relationships between plain water consumption and USG (r = −0.32, P = 0.05). USG was related to sedentary activity/day (r = −0.37, P = 0.03); however, there were no other relationships between physical activity and urine hydration markers or plain water intake (all p's &amp;gt; 0.05). Total healthy eating index score (HEI) was not related to plain water intake (r = 0.16, P = 0.34) but trended with UOsm (r = −0.30, P = 0.07). Further, UOsm was inversely correlated with the specific HEI subcomponents of higher vegetable (Rho = −0.32, P = 0.02) and lower saturated fat (Rho = −0.28, P = 0.04) consumption. Conclusions Water consumption in children was below recommendations, and fruit drinks, carbonated drinks, and juice comprised a significant proportion of beverages consumed. Higher water consumption was correlated with lower urine concentration, providing additional support for the importance of water for hydration in children. Finally, hydration was not related to weight status, % body fat, or habitual physical activity. Funding Sources Danone Research, Palaiseau, France.

A 4-d Water Intake Intervention Increases Hydration and Cognitive Flexibility among Preadolescent Children

Hydration effects on cognition remain understudied in children. This is concerning since a large proportion of US children exhibit insufficient hydration. This study investigated the effects of water intake on urinary markers of hydration and cognition among preadolescents. A 3-intervention crossover design was used among 9- to 11-y-olds [n=75 (43 males, 32 females); 58.2±28.5 BMI percentile]. Participants maintained their water intake [ad libitum (AL)] or consumed high (2.5 L/d) or low (0.5 L/d) water for 4 d. The primary outcomes were performance on cognitive tasks requiring inhibition, working memory, and cognitive flexibility assessed using a modified flanker, go/no-go, and color-shape switch tasks, respectively. Secondary outcomes included urine hydration indices [i.e., color, urine specific gravity (USG), osmolality] assessed using 24-h urine collected during day 4 of each intervention. Repeated-measures ANOVAs were used to assess intervention effects. There was a significant difference in hydration across all 3 interventions. Urine color during the low intervention [median (IQR): 6 (2)] was greater than during AL [5 (2)], and both were greater than during the high intervention [18 (0)] (all P≤0.01). Similarly, osmolality [low (mean ± SD): 912±199 mOsmol/kg, AL: 790±257.0 mOsmol/kg, high: 260±115 mOsmol/kg] and USG [low (mean ± SD): 1.023±0.005, AL: 1.020±0.007, high: 1.005±0.004] during the low intervention were greater during AL, and both were greater than during the high intervention (all P≤0.01). USG and osmolality AL values were related to switch task measures (β: 0.21 to -0.31, P<0.05). Benefits of the high intervention were observed during the switch task, whereby participants exhibited 34% lower working memory cost relative to the low intervention. No significant changes in cognition were observed for the flanker and go/no-go tasks. The water intervention improved urinary markers of hydration and had selective benefits during task switching. Furthermore, children's cognitive flexibility selectively benefits from greater habitual hydration and water intake. This study is registered at clinicaltrials.gov as NCT02816450.

Fluctuation of Water Intake and of Hydration Indices during the Day in a Sample of Healthy Greek Adults.

Mild dehydration may occur during specific periods of the day because of poor hydration habits and/or limited access to a variety of beverages or foods, for example, in work environments. Measurement of hydration indices in spot or in 24 h urine samples may mask mild dehydration in specific periods of the day. Healthy subjects (n = 164; 74 females; age 38 ± 12 years) living in Athens, Greece were enrolled in the study. Subjects recorded their solid food and drink intakes and recorded and collected all urinations for three consecutive days. Water intake was analyzed in 24 h and 6 h periods from wake-up time and scored for variety. Urine hydration indices (osmolality, volume, color, specific gravity) were analyzed in 24 h samples, in morning urine samples and in samples collected in 6 h periods from wake-up time. Fluctuations during the day were significant for the intake of drinking water, hot beverages, milk, fruit and vegetable juices, and alcoholic drinks and for urine osmolality, volume, color, and specific gravity. The urine volume of the first 6 h period after wake-up time (557 ± 231 mL/day) reflects by 76% the 24 h urine collection (1331 ± 144 mL/day). Water intake from all beverages, with the exception of alcoholic beverages, was greater in the first 6h period (morning period) and decreased throughout the day. Hydration indices changed accordingly. The 6 h timed urine sample collected reflects indices in samples collected over 24 h better than any spot urine sample.

Development of Urine Hydration System Based on Urine Color and Support Vector Machine

Nowadays, to maintain hydration in human body has becoming an important issue in health research. The water needs depend on many factors like body size, dietary intake, gender and physical activity, consequently the indicator of hydration status is highly individual. Based on recent research that said the urine color is reliable indicator for hydration status, we would like to develop a prototype for detecting hydration status automatically. To use the color indicator precisely, we tested several color sensors to performance in detecting color and chose TCS34725 as the color sensor. The prototype of urine hydration system (UHS) is designed to record hydration status data in daily basis in cloud computing and the urine information can be accessed by Android smartphone. The prototype employs a set of microcontrollers and sensors as IoT devices and support vector machine (SVM) as a classifier. To evaluate the accuracy of hydration status, we compared the prediction with urine specific gravity (USG) as golden standard. The accuracy of our UHS prototype can reach up to 84%, which is nearly similar with the accuracy of manual prediction using only human eyes.

Hydration and nutrition knowledge in adolescent swimmers. Does water intake affect urine hydration markers after swimming?

Little data exists regarding nutritional knowledge and hydration in adolescent swimmers. The aim of this study was to assess the level of nutrition and hydration knowledge and to describe the fluid balance in adolescent swimmers during training. A study was carried out with a cross-sectional descriptive part and a longitudinal part with repeated measurements over five swimming sessions. Eighty-six adolescent swimmers completed a questionnaire to assess their sport nutrition and hydration knowledge. Fluid balance and urine hydration markers were studied during training. Swimmers showed a limited nutrition knowledge (33.26 % ± SD 12.59) and meagre hydration knowledge (28.61 % ± SD 28.59). Females showed lower scores than male swimmers in nutrition and hydration knowledge. Based on urine specific gravity, swimmers started the training close to the euhydrated threshold (1.019 g/mL ± SD 0.008). Although urine specific gravity and urine colour were reduced after the training, there were minimal changes in body mass (-0.12 Kg ± SD 0.31). Sweat loss (2.67 g/min ± SD 3.23) and the net changes in the fluid balance (-0.22 % ± SD 0.59) were low. The poor knowledge in nutrition and hydration encountered in the swimmers can justify the development of a strategy to incorporate nutritional education programmes for this group. Body water deficit from swimming activity seems to be easily replaced with the water intake to maintain hydration. After the training, the urine of swimmers was diluted regardless of their water intake. Dilution of urine did not reflect real hydration state in swimming.

A MULTIDISCIPLINARY SPORTS MEDICINE PERFORMANCE MODEL IN ELITE WOMENS INTERNATIONAL SOCCER

BackgroundThe traditional sports medicine “backroom” team in elite women's international soccer was comprised of a doctor and physiotherapist(s).ObjectiveTo introduce a multidisciplinary sports medicine performance model into elite women's international soccer...

Cadmium and lead exposure and risk of cataract surgery in U.S. adults.

Cataract is a major cause of visual dysfunction and the leading cause of blindness. Elevated levels of cadmium and lead have been found in the lenses of cataract patients, suggesting these metals may play a role in cataract risk. This study aimed to examine the associations of blood lead, blood cadmium and urinary cadmium with cataract risk. We identified 9763 individuals aged 50 years and older with blood lead and cadmium levels, and a randomly selected subgroup of 3175 individuals with available urinary cadmium levels, from the National Health and Nutrition Examination Surveys (NHANES) from 1999 to 2008 (mean age=63years). Participants were considered to have cataract if they self-reported prior cataract surgery in NHANES's vision examination. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed using survey logistic regression models. We identified 1737 cataract surgery cases (the weighted prevalence=14.1%). With adjustment for age, race/ethnicity, gender, education, diabetes mellitus, body mass index, cigarette smoking (serum cotinine and pack-years) and urine hydration, every 2-fold increase in urinary cadmium was associated with a 23% higher risk of cataract surgery (OR=1.23, 95% CI: 1.04, 1.46, p=0.021). We found no associations of cataract surgery with blood cadmium (OR=0.97, 95% CI: 0.89, 1.07) and blood lead (OR=0.97, 95% CI: 0.88, 1.06). Mediation analysis showed that for the smoking-cadmium-cataract pathway, the ratio of smoking's indirect effect to the total effect through cadmium was more than 50%. These results suggest that cumulative cadmium exposure may be an important under-recognized risk factor for cataract. However, these findings should be interpreted with a caution because of inconsistent results between urinary cadmium and blood cadmium.

Fluid Balance of Adolescent Swimmers During Training.

Swimming, either competitively or leisurely, is a unique activity that involves prolonged exercise while immersed in stable water temperatures. This environment could have an influence on the hydration status of swimmers independently of fluid balance. Forty-six healthy adolescent swimmers (26 males and 20 females; 12.8 ± 2.3 years; 50.6 ± 13.4 kg) were studied during a typical training session in an indoor swimming pool. First morning, prepractice and postpractice urine samples were tested for osmolality and specific gravity, whereas all athletes consumed fluids ad libitum. Sixty-seven percent of the athletes were hypohydrated (urine osmolality [Uosm] ≥700 mmol·kg(-1)) based on their first morning urine sample, which increased to 78% immediately before training. During the 2-hour swimming practice, the minimal sweat loss (0.39 ± 0.27 L) combined with ad libitum fluid availability resulted in unchanged body weight (0.1 ± 0.3 kg). Additionally, thirst was similar (before practice: 46 ± 26, after practice: 55 ± 33 mm on a 100-mm visual analog scale) at pretraining and posttraining time points (p > 0.05). Interestingly, postpractice Uosm was reduced significantly compared with the prepractice value (630 vs. 828 mmol·kg(-1); p = 0.001), without any significant change in body weight (0.1 ± 0.3 kg; p > 0.05). In conclusion, the present data indicated that more than two-thirds of the young swimmers appeared in their practice suboptimally hydrated. Although no changes in body mass were observed during the swimming practice, the decrease in urine hydration markers after swimming might less accurately reflect hydration state.

Influence of Hydration on Physiological and Renal Responses to Hypoxia

Fluid balance is known to alter with hypoxia and exercise, yet the combined effects have not been investigated using a controlled acute hypoxic exposure. Seven healthy participants were hypohydrated 24hrs prior to testing, using exercise and fluid restriction, causing a ~2.5% loss in body mass. Participants then rested in either normoxia with no fluid replacement (NH) or hypoxia (FIO2:0.12) with no fluid (HH), water (HW) or isotonic fluid (HI) replacement over the first 2 hrs of exposure. After 200mins of rest, participants completed an intermittent walking protocol at 50%VO2max. TBW, ICF, ECF, serum s100b, HSP70, ADH and urine hydration markers were taken pre and post exposure. HR, SaO2, core temperature and perceptual scales were monitored throughout. Fluid compartment volumes increased with rehydration and remained at similar values in the isotonic rehydration trial. HSP70 values increased in all trials (HH=1.48, HW=1.00, HI=0.95, NH=0.46pg/L), increases were greater in hypoxia. Serum s100b increased in all hypoxic trials (HH=0.28, HW=0.25, HI=0.09, NH=−0.005μg/L). Hypoxia and hypohydration induced similar physiological strain, which was exacerbated when the two were combined. Hypoxic disruption of the blood brain barrier increased with water intake, suggesting isotonic rehydration is necessary to reduce physiological strain and symptoms of headache and nausea.

Specific gravity and creatinine as corrections for variation in urine concentration in humans, gorillas, and woolly monkeys

Hormones excreted in the urine are widely used to assess the physiological and psychological condition of unrestrained animals. In order to control for variation in the water concentration of urine samples, the hormone concentration is often indexed to the concentration of creatinine. Because there are several problems with using creatinine, we have investigated the efficacy of specific gravity as an alternative basis for adjusting the hormone concentration in humans, gorillas, and woolly monkeys. In an experimental manipulation of human urine hydration, ten volunteers drank a water load proportional to body weight, and provided complete urine collection and saliva samples for four consecutive 20 min intervals. From the urine, we measured cortisol (radioimmunoassay), creatinine (colorimetric assay), and specific gravity (refractometer). Only cortisol was assayed from saliva. During 80 min following water ingestion, cortisol, creatinine, and specific gravity declined as urine became diluted; however, total cortisol excretion remained constant. Only cortisol concentration indexed to specific gravity accurately reflected the consistent cortisol excretion. Specific gravity and creatinine-corrected cortisol values were highly correlated but were significantly different. Salivary cortisol provided evidence for the relative stability of serum cortisol. To determine the utility of these corrections in other primates, we compared specific gravity- and creatinine-corrected cortisol in urine samples from captive gorillas (N=16) and woolly monkeys (N=8). As with the human study, the two corrections were strongly correlated in each species, but the means were different. Specific gravity correction was superior in revealing the circadian variation in cortisol.