24-h Urine Osmolality Research Articles

Habitual water intake impacted the body composition of young male athletes in free-living conditions: a cross-sectional study.

The study aimed to explore the associations between water intake and body composition and differences of body composition in different water itake and hydration statuses among young male athletes. A cross-sectional study was conducted among 111 young male athletes in Beijing, China. Total drinking fluids (TDF) and water from food were assessed using a 7-day, 24-h fluid intake record questionnaire and the duplicate portion method, respectively. The osmolality of 24-hour urine and blood samples was tested. Body composition was measured using a bioelectrical impedance analyzer twice at 5-min intervals. Participants were divided into two groups based on the recommendations of total water intake (TWI) and TDF in China, as well as into three groups based on 24-h urine osmolality. Pearson's correlation coefficients were calculated to determine the relationship between water intake and body composition. Chi-square tests and Student's t-tests were used to compare differences. A total of 109 participants completed the study. TDF (r = 0.230, p = 0.016; r = 0.234, p = 0.014; r = 0.242, p = 0.011) and TWI (r = 0.275, p = 0.004; r = 0.243, p = 0.011; r = 0.243, p = 0.011) were positively correlated with total body water (TBW), intracellular water (ICW), and extracellular water (ECW). TBW/body weight (BW) was positively associated with TDF percentage of BW (TDF/BW) (r = 0.267, p = 0.005), water from food percentage of BW (r = 0.217, p = 0.024), and TWI percentage of BW (TWI/BW) (r = 0.316, p = 0.001). Participants who met the TDF recommendation of China had 1.3 kg higher skeletal muscle mass (SMM), 0.9 kg higher ICW, and 0.5% higher TBW/BW than those who did not (all p < 0.05), with fat-free mass (FFM) and TBW being higher (p = 0.051; p = 0.050). Those who met the TWI recommendation of China had 1.3 kg higher SMM, 2.4 kg higher FFM, 1.1 kg higher ICW, 0.6 kg higher ECW, and 1.7 kg higher TBW than their counterparts (all p < 0.05). Moderate associations were found between water intake and body composition. No significant differences were observed among participants in three hydration statuses (all p > 0.05). Participants who met the TWI or TDF recommendations had better body composition distribution than their counterparts. Thus, habitual water intake, not hydration status, affects body composition among athletes in free-living conditions.

The association between hydration state and the metabolism of phospholipids and amino acids among young adults: a metabolomic analysis

BackgroundWater is vital for humans' survival and general health, which is involved in various metabolic activities. ObjectivesThe aim of this study was to investigate the variation in urine metabolome and associated metabolic pathways among people with different hydration states. MethodsA metabolomic analysis was conducted using 24-h urine samples collected during a cross-sectional study on fluid intake behavior from December 9 to 11, 2021, in Hebei, China. Subjects were divided into the optimal hydration (OH, ≤500 mOsm/kg, n = 21), middle hydration (500–800 mOsm/kg, n = 33), and hypohydration groups (HH, >800 mOsm/kg, n = 13) based on the 3-d average 24-h urine osmolality. Collected 24-h urine samples from 67 subjects (43 males and 34 females) were analyzed for urine metabolome using liquid chromatography-MS. ResultsThe untargeted metabolomic analysis yielded 1055 metabolites by peak intensities. Integrating the results of the orthogonal projections to latent structures discriminant analysis and fold change test, 115 differential metabolites between the OH and HH groups, including phospholipids (PLs) and lysophospholipids, were identified. Among the 115 metabolites identified as differential metabolites, 85 were recorded by the Human Metabolome Database and uploaded to the Kyoto Encyclopedia of Genes and Genomes databases for pathway analysis. Twenty-one metabolic pathways were recognized. Phenylalanine metabolism (0.50, P = 0.007), phenylalanine, tyrosine, and tryptophan biosynthesis (0.50, P = 0.051), glycerophospholipid metabolism (0.31, P < 0.001), sphingolipid metabolism (0.27, P = 0.029), and cysteine and methionine metabolism (0.10, P = 0.066) had the leading pathway impacts. ConclusionsWe found variations in the urinary PLs and amino acids among subjects with different hydration states. Pathways associated with these differential metabolites could further impact various physiologic and pathologic functions. A more comprehensive and in-depth investigation of the physiologic and pathologic impact of the hydration state and the underlying mechanisms to elucidate and advocate optimal fluid intake habits is needed.This trial was registered at Chinese Clinical Trial Registry as ChiCTR2100045268.

#4377 IMPACT OF TOLVAPTAN ON 24H-URINE VOLUME AND OSMOLALITY DURING THE UP-DOSING PHASE IN ADPKD PATIENTS: A SINGLE-CENTER STUDY

Abstract Background and Aims ADPKD is the most prevalent genetic kidney disease. Tolvaptan is the first proven disease-modifying therapy, but is associated with aquaretic side effects, frequently leading to treatment discontinuation. Therefore, identifying factors, which can ameliorate the aquaretic side effects and facilitate therapy is crucial. Previous data reported 24h-osmolar excretion in urine or GFR as the main determinants of urine volume on tolvaptan but included only few patients. This study's objective was to prospectively examine the 24-hour urine volume and urine osmolality during the up-dosing phase of tolvaptan in a cohort with a moderate sample size and different subgroups in order to identify modifiable and non-modifiable factors for urine volume increase. Finally, quality of life (QoL) during tolvaptan treatment was investigated in relation to urine volume since these data are scarce thus far and provide crucial insights into the therapy burden. Method Analysis of 24-h urine collection at baseline and at least once on tolvaptan was carried out for 75 patients (complete cohort). For 35 patients (longitudinal cohort) urine collections were available for baseline and all three tolvaptan doses (45/15 mg, 60/30 mg and 90/30 mg). All patients are participants of the German AD(H)PKD registry. Sodium, protein and potassium intake were calculated from excretion in 24h-urine and QoL was assessed by the Short Form-12 (SF-12) questionnaire. Statistical analyses were computed using R statistical software. A p-value of &amp;lt; 0.05 was regarded as significant. Results The mean age of the patients in the complete cohort was 41.3 ± 10.7 (range 18-64 years) with a mean eGFR of 67.3 ± 27.2 ml/min/1.73m2 and was similar to the longitudinal cohort with a mean age of 41.8 ± 10.1 (23-64 years) and eGFR of 69.4 ± 27.5ml/min/1.73m2. A significant increase (p&amp;lt; 0.0001) in 24-h urine volume (138%) occurred only immediately after therapy initiation with no further significant increase during updosing in the complete and longitudinal cohort. In line with this 24h-urine osmolality decreased (57%) significantly (p&amp;lt; 0.0001) only after beginning of treatment and remained almost unchanged after updosing. Total solutes, protein and sodium intake showed non-significant changes across all doses. There were no significant differences in urine volume between gender, age classes (&amp;lt;45 vs. ≥45 years), or Mayo class when examining the various subgroups. Considering modifiable factors, 24h-urine volume was positively correlated with eGFR on tolvaptan reaching significance on 45/15 mg (p = 0.013) and 90/30 mg (p = 0.027). Patients &amp;lt;45 years and patients with an eGFR ≥ 60 ml/min/1.73m2 experienced a significantly higher relative urine volume increase at the beginning (p = 0.0332 vs. ≥45 years and p = 0.0097 vs eGFR &amp;lt; 60 ml/min/1.73m2) in the complete cohort. In multivariable linear regression analyses containing modifiable and non-modifiable covariates only sodium intake had a significant impact in tolvaptan-naive patients (p = 0.0064), while on tolvaptan age (p = 0.0008) and weight (p = 0.0190) became significant together with sodium intake (p = 0.0008) and potassium intake (p = 0.0040). Across the three tolvaptan doses no significant differences between the number of patients reaching pre-defined osmolality goals (&amp;lt; 250 mosmol/kg for spontaneous urine and &amp;lt; 150 mosmol/kg for 24h-urine) could be detected. Before and after tolvaptan treatment, neither the mental nor physical QoL changed significantly. Conclusion Our study showed that the significant rise in urine volume occurs immediately after therapy initiation with only minor and non-significant increases upon further updosing. Urine osmolality decreases significantly directly after start of tolvaptan and remains constant with most patients achieving adequate suppression of urine osmolality. Patient counseling should consider that younger patients and patients with better eGFR might experience stronger urine volume increase at the beginning and advising to reduce salt and potassium intake can ameliorate aquaretic side effects. Tolvaptan treatment showed no negative impact on QoL but further investigations in larger cohorts are needed.

Online Arabic Beverage Frequency Questionnaire (ABFQ): evaluation of validity and reliability

BackgroundObesity and chronic diseases are significant public health issues in the Middle East and North Africa region. A robust body of evidence demonstrated the association between beverage consumption, obesity, and chronic diseases. Therefore, the assessment of beverage consumption is gaining more interest in health policy development, food industry partnerships, research expansion and community involvement. Although beverage-consumption assessment tools have been developed for various populations, none were developed for the Arabic population. In this study, we developed and validated an online Arabic Beverage Frequency Questionnaire (ABFQ) to assess the total beverage intake among Arabic speaking population.MethodsA cross-sectional validation study was conducted among healthy adults aged between 18 and 55 years. Participants (n = 49) completed a 24-item ABFQ on two occasions and provided one 24-h urine sample. For validity, total beverage consumption (ABFQ1) was assessed against a 24-h urine sample using an osmolality test and correlation analysis. Reliability was assessed by comparing the participants’ consumption in total and for every 24 individual items from ABFQ1 with the total and individual items in ABFQ2 using correlation and paired sample t-test.ResultsThe average daily consumption of beverages was 1504 ml/day, while the average urine osmolality/kg was 614. The validity assessment between ABFQ and urine osmolality indicates a negative correlation. However, the correlation was week and not statistically significant (rs = -0.2, p = 0.12). In reliability test, correlation analysis was positive and acceptable in all beverage categories (rs = 0.4 − 0.9; all p < 0.05) except flavored milk (rs = 0.2; p < 0.181) and sweetened coffee (rs = 0.3; p < 0.022). Furthermore, no significant differences were found between the means of total consumption in both ABFQ1 and ABFQ2.ConclusionsThe finding of this study suggest that the ABFQ is a reliable reproducible tool for assessing beverage consumption among Arabic-speaking consumers. However, the survey could not be validated using 24-h urine osmolality only and other methods such as multi dietary records may use in future re-assessment.

The relationship between water intake, hydration biomarkers and physical activity of young male athletes in Beijing, China: A cross-sectional study.

To explore the relationship between water intake, hydration biomarkers and physical activity of young male athletes. A 7-day cross-sectional study was conducted among 45 male athletes aged 18-25 years in Beijing, China. Total drinking fluids (TDF) was obtained using 7-day 24-h fluid intake questionnaire. Water from food (WFF) was assessed using the methods of food weighing, duplicate portion method and laboratory analysis. Physical activity was evaluated using physical activity energy expenditure (PAEE) and metabolic equivalent of task (MET). Totally, 42 participants completed the study. The medians of total water intake (TWI), TDF and WFF of participants were 2771 mL, 1653 mL and 1088 mL respectively. Jonckheere-Terpstra test showed a significant increase trend toward higher TWI and TDF with higher PAEE level (Z=2.414, p=0.016; Z=2.425, p=0.015). Spearman's rank correlation showed that TWI was positively correlated with PAEE (rs=0.397, p=0.009). TDF showed a positive correlation with PAEE and MET (rs=0.392, p=0.010; rs=0.315, p=0.042). The median urine volume was 840 mL, urine specific gravity was 1.020, and 24-h urine osmolality was 809 mOsm/kg. Significant differences were found in plasma cortisol among the four MET groups (χ2=8.180; p=0.042). Young male athletes with higher physical activity level had higher amounts of TWI and TDF than their counterparts but had similar hydration biomarkers. There was a high incidence of dehydration in athletes, and attentions need to be paid on the intake of TDF among them to maintain the optimal hydration status.

Total water intake guidelines are sufficient for optimal hydration in United States adults.

Recent studies suggest that 24-h urine osmolality (UOsm) for optimal water intake should be maintained < 500mmol·kg-1. The purpose of this study was to determine the total water intake (TWI) requirement for healthy adults to maintain optimal hydration as indicated by 24-h urine osmolality < 500mmol·kg-1. Twenty-four-hour UOsm was assessed in 49 men and 50 women residing in the United States (age: 41 ± 14 y, body mass index: 26.3 ± 5.2kg·m-2). TWI was assessed from 7-day water turnover, using a dilution of deuterium oxide, corrected for metabolic water production. The diagnostic accuracy of TWI to identify UOsm < 500mmol·kg-1 was evaluated using receiver operating characteristic (ROC) analysis in men and women separately. Twenty-four-hour UOsm was 482 ± 229 and 346 ± 182mmol·kg-1 and TWI was 3.57 ± 1.10L·d-1 and 3.20 ± 1.27L·d-1 in men and women, respectively. ROC analysis for TWI detecting 24-h UOsm < 500mmol·kg-1 in men yielded an area under the curve (AUC) of 77.4% with sensitivity, specificity, and threshold values of 83.3%, 64.5%, and 3.39L·d-1, respectively. The AUC was 82.4% in women with sensitivity, specificity, and threshold values of 85.7%, 72.1%, and 2.61L·d-1. Considering threshold values in men and women of 3.4L·d-1 and 2.6L·d-1, respectively, maintaining TWI in line with National Academy of Medicine guidelines of 3.7L·d-1 in men and 2.7L·d-1 in women should be sufficient for most individuals in the United States to maintain 24-h UOsm < 500mmol·kg-1.

Urine osmolality predicts calcium-oxalate crystallization risk in patients with recurrent urolithiasis.

Our aim was to investigate the validity of osmolality from 24-h urine collection in examining the risk for calcium-oxalate (CaOx) kidney stone formation in patients with recurrent urolithiasis. Three hundred and twelve subjects (males/females: 184/128) from France with a history of recurrent kidney stones from confirmed or putative CaOx origin were retrospectively included in the study (46 ± 14 years, BMI: 25.3 ± 5.0kg·m-2). Tiselius' crystallization risk index (CRI) was calculated based on urinary calcium, oxalate, citrate, magnesium, and volume from 24-h samples. The diagnostic ability of 24-h urine osmolality to classify patients as high risk for kidney stone crystallization was examined through the receivers operating characteristics analysis. High risk for CaOx crystallization was defined as CRI > 1.61 and > 1.18, for males and females, respectively. The accuracy of urine osmolality to diagnose risk of CaOx stone formation (AUC, area under the curve) for females was 84.6%, with cut-off point of 501mmol·kg-1 (sensitivity: 83.3%, specificity: 76.0%). Males had AUC of 85.8% with threshold of 577mmo·kg-1 (sensitivity: 85.5%, specificity: 77.6%). A negative association was found between 24-h urine volume and osmolality (r = -0.63, P < 0.001). Also, a positive association was found between 24-h urine osmolality and CRI (r = 0.65, P < 0.001), as well as urea excretion with CRI (r = 0.37, P < 0.001). In conclusion, urine osmolality > 501 and > 577mmol·kg-1, infemale and in male, respectively, was associated with a risk for CaOx kidney stone formation in patients with a history of recurrent urolithiasis. Thus, when CaOx origin is confirmed or suspected, 24-h urine osmolality provides a simple way to define individualized target of urine dilution to prevent urine crystallization and stone formation.

Acute Increases in Water Consumption Supress Copeptin in Low Drinkers

Abstract Objectives To assess the acute effect of adequate water consumption on copeptin, a marker of arginine vasopressin, in low drinkers. Methods Six healthy (5 males, 1 female) low drinkers (age 43 ± 7 y, BMI 30.5 ± 3) were recruited based on self-reported daily water consumption ≤1.5 L·day−1 in males or 1.0 L·day−1 in females (854 ± 432 mL·d−1) and 24-h urine osmolality ≥800 mmol·kg−1 (968 ± 114 mmol·kg−1). Participants completed two counterbalanced crossover 11-h protocols. They were provided either the Institute of Medicine's recommended amount of water excluding food (males: 3 L, females: 2 L, HWI) or an amount representing the bottom quartile of water consumption observed in the National Health and Nutrition Examination Survey (males: 0.5 L, females: 0.4 L, LWI). Food was provided to participants and standardized to body weight (100 kJ·Kg−1) using a consistent ratio of macronutrients. Blood samples were collected at hours 700, 800, 900, 1200, 1300, 1400, 1600, 1700, and 1800. Results There was a significant main effect of water intake on plasma osmolality (F = 11.838, P = 0.018) with greater values in LWI at 1200 (HWI: 287 ± 3, LWI: 291 ± 3; P = 0.013), 1400 (HWI: 287 ± 4, LWI: 291 ± 5; P = 0.049), and 1700 (HWI: 287 ± 2, LWI: 292 ± 4; P = 0.004). There was also a significant main effect of water intake on copeptin (F = 9.848, P = 0.026) with higher values in LWI at 0800 (HWI: 6.1 ± 2.3, LWI: 8.7 ± 3.7; P = 0.016), 0900 (HWI: 5.3 ± 2.4, LWI: 9.2 ± 4.5; P = 0.013), 1200 (HWI: 4.2 ± 1.9, LWI: 7.8 ± 4.6; P = 0.021), 1400 (HWI: 4.3 ± 1.8, LWI: 8.3 ± 4.7; P = 0.033), 1600 (HWI: 4.7 ± 2.5, LWI: 7.6 ± 4.5; P = 0.049), and 1800 (HWI: 4.4 ± 2.5, LWI: 7.8 ± 5.2; P = 0.048). Water intake did not influence change in plasma volume (P = 0.214). Conclusions Copeptin was suppressed in response to acute increases in water consumption via suppression of plasma osmolality. Copeptin may serve as a sensitive marker for changes in total water intake. Funding Sources This study was supported by Arizona State University College of Health Solutions.

Twenty-four-hour urine osmolality as a representative index of adequate hydration and a predictor of recurrence in patients with urolithiasis.

To determine the value of 24-h urine osmolality (UOsm) as a representative index of adequate hydration and predictor of stone recurrence in patients with urolithiasis. Medical records of consecutive patients presenting with renal or ureteric stones between 1994 and 2017 were retrospectively reviewed. Patients were grouped according to the results of 24-h UOsm (low ≤ 564mOsm/kg H2O, high > 564mOsm/kg H2O). Metabolic parameters and risk of stone recurrence were compared between the two groups. The low urine concentration group were more likely to be older, to be female, and to have a lower body mass index and higher glomerular filtration rate than the high concentration group (each P < 0.005). A positive correlation was seen between 24-h UOsm and urinary calcium, sodium, uric acid, and magnesium excretion and 24-h specific gravity; a negative correlation was seen with 24-h urine volume. Stone-forming constituents, such as calcium and uric acid, were significantly higher in the high urine concentration group. Kaplan-Meier estimates showed that the low urine concentration group had a significantly longer stone recurrence-free period than the high urine concentration group (log-rank test, P < 0.001). In multivariate Cox regression analyses, 24-h UOsm was seen to be an independent risk factor for stone recurrence. UOsm is a promising approach to assessing hydration and predicting stone recurrence in patients with urolithiasis. Maintaining UOsm < 564mOsm/kg H2O may reduce the risk of stone recurrence.

Increasing Water Intake Reduces High Copeptin in Healthy Adults

Plasma copeptin, a surrogate marker for vasopressin (AVP), is an independent risk factor for diabetes mellitus. Higher AVP and copeptin have also been observed in individuals with low water intake. In this study, we tested the effect of six weeks water supplementation (1.5 L·day−1) on fasting plasma copeptin (PCop) concentration and urinary hydration parameters in habitual low‐drinkers identified by screening for high copeptin (PCop ≥ 10.7 pmol·L−1 in men and ≥ 6.1 pmol·L−1 in women) in stored plasma samples originally collected in 2013–2015 as part of the population‐based Malmö Offspring Study (MOS).From the 24% of the MOS population who had high copeptin, we enrolled thirty‐one healthy adults who in addition had a 24h urine osmolality (UOsm) &gt; 600 mOsm·kg−1 at the baseline of the current study (i.e. 2.8±0.8 years after MOS). At baseline (Pre) and at the end of the six‐week water supplementation (Post), 24h urine collections for UOsm and urine volume (UVol), and fasting plasma samples for measurement of PCop and electrolytes (sodium, PNa) were obtained. In addition, a four‐day web‐based food and fluid record was completed Pre and Post intervention. Depending on distribution, Pre vs. Post differences were assessed with paired t‐test or Wilcoxon's paired rank test. Unless stated otherwise, data are presented as median [25th; 75th percentiles].The water intervention was effective in increasing mean (min; max) plain water intake from 427 (272; 582) to 1352 (997; 1707) g·day−1 (P &lt; 0.0001), with no other observed changes in diet. This was supported by a reduction in UOsm (Pre: 879 [705; 996]; Post: 384 [319; 502] mOsm·kg−1; P &lt; 0.001) and an increase in UVol (Pre: 1.06 [0.90; 1.20]; Post: 2.27 [1.52; 2.67] L·d−1; P &lt; 0.001). The intervention slightly reduced mean (min; max) PNa from 141 (137–145) to 140 (137–144) mmol·L−1 without inducing any cases of hyponatremia. At baseline, PCop was 12.9 [7.4; 21.9] pmol·L−1 and did not differ from the population screening in MOS nearly three years earlier (PCop 11.8 [10.1; 13.8] pmol·L−1; P = 0.367). Six weeks of increased water intake resulted in a significant reduction of PCop (Post: 7.8 [4.6; 11.3] pmol·L−1; P &lt; 0.001). Moreover, participants in the top tertile of baseline PCop (35.2 [21.0; 66.5] pmol·L−1) had a significantly greater reduction compared to the bottom two tertiles (−28.2 [−8.1; −58.6] vs. −1.6 [−0.3; −4.5] pmol·L−1; P &lt; 0.001) but were otherwise similar in clinical characteristics.In conclusion, water supplementation in subjects with high copeptin is effective in lowering copeptin and appears as a safe and promising intervention with potential of lowering risk of diabetes mellitus.Support or Funding InformationThis study was supported by grants from the Swedish National Research Council, The Wallenberg Foundation Clinical Scholar, The Swedish Heart and Lung Foundation, The Göran Gustafsson Foundation and funding from Danone Research.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Upper metastable limit osmolality of urine as a predictor of kidney stone formation in children

High fluid intake has been universally recommended for kidney stone prophylaxis. We evaluated 24-h urine osmolality regarded as the best biomarker of optimal hydration and upper metastable limit osmolality after water evaporation from urine sample to the onset of spontaneous crystallization and its usefulness as a new risk index that would describe an individual lithogenic potential. We collected 24-h urine from 257 pediatric patients with kidney stones and 270 controls. After volume and osmolality assessment, the urine samples were subjected to volume reduction in vacuum rotavapor continued to the onset of an induced urinary crystallization. The upper metastable limit osmolality of urine sample was calculated based on its initial osmolality value and the amount of water reduction. Pediatric stone formers presented with higher urine volume and lower urine osmolality than healthy controls. Despite that, their urine samples required much lower volume reduction to induce the spontaneous crystallization than those of controls. The ROC analysis revealed an AUC for the upper metastable limit osmolality of 0.9300 (95% CI 0.9104–0.9496) for distinguishing between stone formers and healthy subjects. At the cutoff of 2696 mOsm/kg, the test provided sensitivity and specificity of 0.8638 and 0.8189, respectively. 24-h urine osmolality provided the information about current hydration status, whereas evaporation test estimated the urinary potential to crystalize dependent on urine composition. Upper metastable limit osmolality may estimate the individual lithogenic capability and identify people at risk to stone formation when exposed to dehydration.

Fluid consumption pattern and hydration among 8-14 years-old children.

Children consume various fluids to meet dietary water intake needs. However, the contribution of different fluid types on hydration is unclear. The purpose of this study was to develop fluid intake patterns and examine their association with hydration, as indicated by 24-h urine osmolality. Two hundred ten (105 girls) healthy children (height: 1.49 ± 0.13 m, weight: 43.4 ± 12.6 kg, body fat: 25.2 ± 7.8%) recorded their fluid intake for two consecutive days, and collected their urine for 24-h during the 2nd day, while conducting their normal daily activities. Urine samples were analyzed for specific gravity and osmolality. Factor analysis with principal components method was applied to extract dietary patterns from six fluid groups. Linear regression analysis evaluated the associations between the extracted dietary patterns and hydration based on 24-h urine osmolality. The analysis revealed the following six components: 1, characterized by consumption of milk and fresh juice, but not packaged juice; 2, by regular soda and other drinks, but not water; 3, by fresh juice and other drinks; 4, by packaged juice, but not regular soda; 5, by water and milk; and 6, by fresh juice. Component 5 was negatively correlated with urine osmolality (P = 0.001) indicating better hydration, whereas component 2 was positively correlated with urine osmolality (P = 0.001). A drinking pattern based on water and milk was associated with better hydration, as indicated by lower urine osmolality, whereas drinking regular soda and other drinks but not water was associated with inferior hydration.

A Cross-Sectional Study on the Association between 24-h Urine Osmolality and Weight Status in Older Adults.

Data on the association between hydration and body weight in the elderly are scarce. The objective of this work was to quantify the association between 24-h urine osmolality and weight status in the elderly. A cross-sectional study was conducted within the Nutrition UP 65 study. A quota sampling was implemented to achieve a nationally representative sample of Portuguese older adults (≥65 years) according to age, sex, education and region. From a sample size of 1500 participants, 1315 were eligible for the present analysis, 57.3% were women and 23.5% were aged ≥80 years. Participants were grouped using tertiles of 24-h urine osmolality by sex. World Health Organization cutoffs were used to classify participants according to weight status. Multinomial multivariable logistic regression models were conducted to evaluate the association of tertiles of osmolality with weight status, adjusting for confounders. Odds Ratios (OR) and respective 95% Confidence Intervals (95% CI) were calculated. Being in the 3rd urine osmolality tertile (highest) was associated with a higher risk of being obese in men, OR = 1.97, 95% CI = 1.06, 3.66. No such association was found in women. These results highlight the need for implementing studies in order to clarify the association between hydration and weight status in the elderly.

Effect of increased water intake on plasma copeptin in healthy adults

PurposeInter-individual variation in median plasma copeptin is associated with incident type 2 diabetes mellitus, progression of chronic kidney disease, and cardiovascular events. In this study, we examined whether 24-h urine osmolality was associated with plasma copeptin and whether increasing daily water intake could impact circulating plasma copeptin.MethodsThis trial was a prospective study conducted at a single investigating center. Eighty-two healthy adults (age 23.6 ± 2.9 years, BMI 22.2 ± 1.5 kg/m2, 50% female) were stratified based upon habitual daily fluid intake volumes: arm A (50–80% of EFSA dietary reference values), arm B (81–120%), and arm C (121–200%). Following a baseline visit, arms A and B increased their water intake to match arm C for a period of 6 consecutive weeks.ResultsAt baseline, plasma copeptin was positively and significantly associated with 24-h urine osmolality (p = 0.002) and 24-h urine specific gravity (p = 0.003) but not with plasma osmolality (p = 0.18), 24-h urine creatinine (p = 0.09), and total fluid intake (p = 0.52). Over the 6-week follow-up, copeptin decreased significantly from 5.18 (3.3;7.4) to 3.90 (2.7;5.7) pmol/L (p = 0.012), while urine osmolality and urine specific gravity decreased from 591 ± 206 to 364 ± 117 mOsm/kg (p < 0.001) and from 1.016 ± 0.005 to 1.010 ± 0.004 (p < 0.001), respectively.ConclusionsAt baseline, circulating levels of copeptin were positively associated with 24-h urine concentration in healthy young subjects with various fluid intakes. Moreover, this study shows, for the first time, that increased water intake over 6 weeks results in an attenuation of circulating copeptin.Clinical Trial Registration Number NCT02044679.

Hydration, Fluid Intake, and Related Urine Biomarkers among Male College Students in Cangzhou, China: A Cross-Sectional Study-Applications for Assessing Fluid Intake and Adequate Water Intake.

The objectives of this study were to assess the associations between fluid intake and urine biomarkers and to determine daily total fluid intake for assessing hydration status for male college students. A total of 68 male college students aged 18–25 years recruited from Cangzhou, China completed a 7-day cross-sectional study. From day 1 to day 7; all subjects were asked to complete a self-administered 7-day 24-h fluid intake record. The foods eaten by subjects were weighed and 24-h urine was collected for three consecutive days on the last three consecutive days. On the sixth day, urine osmolality, specific gravity (USG), pH, and concentrations of potassium, sodium, and chloride was determined. Subjects were divided into optimal hydration, middle hydration, and hypohydration groups according to their 24-h urine osmolality. Strong relationships were found between daily total fluid intake and 24-h urine biomarkers, especially for 24-h urine volume (r = 0.76; p < 0.0001) and osmolality (r = 0.76; p < 0.0001). The percentage of the variances in daily total fluid intake (R2) explained by PLS (partial least squares) model with seven urinary biomarkers was 68.9%; two urine biomarkers—24-h urine volume and osmolality—were identified as possible key predictors. The daily total fluid intake for assessing optimal hydration was 2582 mL, while the daily total fluid intake for assessing hypohydration was 2502 mL. Differences in fluid intake and urine biomarkers were found among male college students with different hydration status. A strong relationship existed between urine biomarkers and fluid intake. A PLS model identified that key variables for assessing daily total fluid intake were 24-h urine volume and osmolality. It was feasibility to use total fluid intake to judge hydration status.

Criterion values for urine-specific gravity and urine color representing adequate water intake in healthy adults

Growing evidence suggests a distinction between water intake necessary for maintaining a euhydrated state, and water intake considered to be adequate from a perspective of long-term health. Previously, we have proposed that maintaining a 24-h urine osmolality (UOsm) of ⩽500 mOsm/kg is a desirable target for urine concentration to ensure sufficient urinary output to reduce renal health risk and circulating vasopressin. In clinical practice and field monitoring, the measurement of UOsm is not practical. In this analysis, we calculate criterion values for urine-specific gravity (USG) and urine color (UCol), two measures which have broad applicability in clinical and field settings. A receiver operating characteristic curve analysis performed on 817 urine samples demonstrates that a USG ⩾1.013 detects UOsm>500 mOsm/kg with very high accuracy (AUC 0.984), whereas a subject-assessed UCol⩾4 offers high sensitivity and moderate specificity (AUC 0.831) for detecting UOsm >500 m Osm/kg.

Urine osmolality in treatment-naïve HIV-positive subjects in Southeast Nigeria.

Urine osmolality varies over a wide range of values in a healthy state. Dilute urine or concentrated urine may be observed in many environmental, physiologic, and disease conditions. Urine osmolality is not commonly evaluated in routine clinical practice and in human immunodeficiency virus (HIV) subjects. The factors that influence urine osmolality have not been completely identified. The aim of this study was to evaluate urine osmolality in treatment-naïve HIV subjects and to identify the factors that may influence dilute and concentrated urine in this group of patients. This was a cross-sectional study of treatment-naive HIV subjects conducted in Federal Medical Centre (FMC), Owerri, Nigeria. Demographic and anthropometric data were obtained. Urine osmolality and other relevant investigations were conducted. Normal urine osmolality was defined as 24-h urine osmolality (24 HUOsm) 300-750 mOsm/kgH2O, dilute urine as 24 HUOsm 2O and concentrated urine as 24 HUOsm> 750 mOsm/kgH2O. The association between the variables and urine osmolality and the strength of variables to predict dilute urine and concentrated urine were determined. The mean 24HUOsm was 564 ± 501 mOsm/kgH2O and the mean spot urine osmolality (SUOsm) 464 ± 271 mOsm/kgH2O. Normal urine osmolality was observed in 29.6%, dilute urine in 64.5%, and concentrated urine in 5.9% of the HIV subjects. There was a significant association between urine osmolality and body mass index (BMI), creatinine clearance, as well as serum cholesterol level. Only high-density lipoprotein cholesterol (HDL) predicted dilute urine, whereas BMI, spot urine protein, 24-h urine protein, spot urine creatinine, serum HDL, and CD4 cell count predicted concentrated urine. The prevalence of dilute urine was high among the treatment-naïve HIV subjects. Abnormalities of serum lipids, renal function, and weight were common in treatment-naïve HIV subjects who had dilute urine. There is a need for clinicians to routinely assess urine osmolality and further diagnose for dyslipidemia, renal function impairment, and abnormal weight in HIV subjects at the early stage of the infection.

Water Turnover, Urinary Markers Of Hydration, And Mood In Men And Women

PURPOSE: Past research has identified relationships between daily total water intake (TWI) measured by diet diary with dimensions of mood in free living, and laboratory confined men and women. However, diet records have been associated with subjective errors and thus these findings should be confirmed in objective of body water turnover (WTO). METHODS: 49 women (42±14y, 164±6cm, 71±16kg) and 46 men (40±14y, 177±7cm, 81±16kg) volunteered for WTO measurement via deuterium oxide dilution technique over two consecutive weeks. Total water intake (TWI) was calculated as WTO (L·d-1) - metabolic water production. The Profile of Mood State questionnaire (POMS) was administered in the morning on the 4th day of each week. Physical activity was assessed with the International Physical Activity Questionnaire. The influence of the prior days, and acute hydration status (via urine osmolality) on mood was considered with; a) 24h urine collections comprised of the full day leading up to, and, b) single urine samples collected immediately prior to completion of the POMS. Measurements were averaged between weeks. Multivariate linear regression was completed to assess if WTO or either of the hydration markers predicted any of the 6 POMS sub-scales or the composite mood measurement of total mood disturbance, over and above the influence of age, body mass index, and MET minutes of physical activity completed during the week. RESULTS: The vigor sub-scale of was significantly associated with WTO, (Fchange[1,94]=5.00, R2change=0.05, Beta=0.23, P=0.03). This finding was not apparent in relationships with 24h urine osmolality (Fchange[1,94]=2.58, R2change=0.03, Beta=0.16, P=0.11) or single sample urine osmolality (Fchange[1,94]=2.65, R2change=0.03, Beta=-0.17, P=0.10). No other sub-scales or TMD were significantly related to WTO, or hydration indices, after accounting for the covariates. CONCLUSIONS: This study confirms a positive relationship between mood and fluid intake using direct measurement of WTO. The lack of significance to urinary hydration markers is indicative of the multi-faceted composition of urine concentration (i.e., kcal, protein intake, etc.). However, daily WTO is modestly associated with mood and should be further explored in controlled laboratory conditions to further elucidate this relationship.

Evaluation of 24h Urine Volume as an Indicator of Uosm:Posm Ratio and Free Water Clearance in Pregnant Women

Free water clearance (FWC), calculated from urine and blood measures, is often used to describe body water balance via the kidney's regulation of diuresis. The purpose of this investigation was to evaluate if 24h urine volume was a significant predictor of the urine-to-serum osmolality ratio (USR) and FWC in pregnant (PREG) and non-pregnant (CON) women. Methods: 24h urine volume (Uvol), 24h urine osmolality, and serum osmolality were measured in 18 PREG (age: 31±3y, height: 1.66±0.07m; pre-pregnancy weight: 68.08±18.92kg) women at the end of the first, second, and third trimesters, and in 18 CON (age: 29±4y; height: 1.64±0.08m; weight: 64.83±13.84kg) at similar time intervals for calculation of USR and FWC. Relationships between 24h Uvol and USR, as well as 24h Uvol and FWC, were evaluated with linear regression. Results: 24h Uvol was a significant predictor of USR (PREG: r2=0.61, p<0.0001; CON: r2=.50, p<0.0001) and FWC (PREG: r2=0.70, p<0.0001; CON: r2=.45, p<0.0001); relationships were similar between PREG and CON for 24h Uvol and USR (p=0.24) and for 24h Uvol and FWC (p=0.90). Conclusion The relationships between 24h Uvol and both USR and FWC are maintained throughout pregnancy. This suggests that 24h Uvol may provide adequate diagnostic accuracy for the evaluation of body water balance during pregnancy. Supported by Danone Research.

Afternoon Spot Urine Osmolality as a Biomarker of Hydration in Free‐living Healthy Adults

ObjectivePrevious research has highlighted links between fluid intake (FI), hydration parameters, and disease risk. Specifically, hydration markers in 24h urine samples respond quickly to a change in FI and have been linked to risk of CKD and lithiasis. However, 24h urine collection is burdensome, inconvenient, and time consuming. Spot urine collections would simplify daily hydration monitoring for researchers, clinicians, and individuals. Therefore, we assessed the equivalence of 24h and spot urine osmolality (24h Uosm; Spot Uosm) to determine whether a single spot may replace 24h collection.Methods82 healthy adults with low to high habitual FI (50%M; age 23.6±2.9 y; BMI 22.2±1.5 kg/m2) recorded all fluid consumed and collected individual voids over 24h. Uosm was measured on each void and on the pooled 24h sample. Equivalence between Spot and 24h Uosm was evaluated using the Two One‐Sided Test method (α=0.025).ResultsSpot Uosm from afternoon samples (14:00‐16:00; 16:00‐18:00; 18:00‐20:00) was equivalent to 24h Uosm whereas morning (08:00‐10:00; 10:00‐12:00) and midday (12:00‐14:00) spots tended to overestimate 24h Uosm. The mean [95% CI] difference between 24h and Spot Uosm was 287 [209;365] between 08:00‐10:00; 83 [12;154] between 10:00‐12:00; and 107 [58;157] between 12:00‐14:00. From 14:00‐16:00; 16:00‐18:00; and 18:00‐20:00, the mean difference was ‐25 [‐72;22]; 29 [‐35;92] and 12 [‐41;66].ConclusionAfternoon Spot Uosm is equivalent to 24h Uosm. Thus, short, well‐timed urine collections may represent a convenient alternative to 24h samples, providing an easy way to monitor daily hydration in real‐life conditions. Afternoon Spot could also serve as an early warning signal to increase FI for maintaining 24h euhydration.