Search

Purpose: Recent studies suggest that 24-h urine osmolality (UOsm) for optimal water intake should be maintained < 500 mmol·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 < 500 mmol·kg -1 ., Methods: 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 ± 5.2 kg·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 < 500 mmol·kg -1 was evaluated using receiver operating characteristic (ROC) analysis in men and women separately., Results: Twenty-four-hour UOsm was 482 ± 229 and 346 ± 182 mmol·kg -1 and TWI was 3.57 ± 1.10 L·d -1 and 3.20 ± 1.27 L·d -1 in men and women, respectively. ROC analysis for TWI detecting 24-h UOsm < 500 mmol·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 3.39 L·d -1 , respectively. The AUC was 82.4% in women with sensitivity, specificity, and threshold values of 85.7%, 72.1%, and 2.61 L·d -1 ., Conclusion: Considering threshold values in men and women of 3.4 L·d -1 and 2.6 L·d -1 , respectively, maintaining TWI in line with National Academy of Medicine guidelines of 3.7 L·d -1 in men and 2.7 L·d -1 in women should be sufficient for most individuals in the United States to maintain 24-h UOsm < 500 mmol·kg -1 ., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany.)

Background: Emerging evidence links underhydration and habitual low water intake to higher cardiometabolic risk, but evidence is limited in community-dwelling older adults., Objectives: The objective is to examine if higher water intake and better hydration are associated with better cardiometabolic health., Methods: This cross-sectional analysis using general linear models included 2238 participants from the Framingham Heart Study Second Generation and First Generation Omni cohorts with an estimated glomerular filtration rate >30 mL·min-1·1.73 m-2 and a valid FFQ for assessment of water intake. Of these participants, 2219 had fasting spot urinary creatinine data and 950 had 24-h urine creatinine data to assess hydration. Cardiometabolic risk factors included fasting glucose, triglycerides (TGs), total cholesterol (TC), HDL cholesterol, and calculated LDL cholesterol; glycated hemoglobin (HbA1c); C-reactive protein (CRP); and systolic (SBP) and diastolic (DBP) blood pressure., Results: The combined cohorts were on average aged 70 y; 55% were women. Mean (95% CI) daily total water intakes were 2098 (2048, 2150) mL for men and 2109 (2063, 2156) mL for women. Total daily water, beverage (including plain water), and plain water intakes demonstrated significant positive trends with HDL cholesterol (P < 0.01). TG concentrations were significantly lower among the highest plain water consumers (P < 0.05). The 24-h urine concentration, as measured by creatinine, was positively associated with LDL cholesterol and TG concentrations ( P < 0.01) and inversely associated with HDL cholesterol concentrations (P < 0.002). Neither water intake nor urine concentration was associated with glucose or HbA1c (P > 0.05)., Conclusions: Our findings of a consistent pattern between circulating lipid concentrations and different water sources and hydration markers support an association between hydration and lipid metabolism in older adults and add to the growing evidence that inadequate water intake and underhydration may lead to higher cardiometabolic risk., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society for Nutrition.)

The idea that water intake or hydration may play an intrinsic, independent role in modulating metabolic disease risk is relatively recent. Here, we outline the journey from early experimental works to more recent evidence linking water and hydration to metabolic health. It has been known for decades that individuals with existing metabolic dysfunction experience challenges to body water balance and have elevated arginine vasopressin (AVP), a key hormone regulating body fluid homeostasis. Later, intervention studies demonstrated that altering fluid balance in these individuals could worsen their condition, suggesting that hydration played a role in modulating glycemic control. More recently, observational and interventional studies in healthy individuals have implicated the hydration-vasopressin axis in the pathophysiology of metabolic diseases. Individuals with higher AVP (or its surrogate, copeptin) are at higher risk for developing type 2 diabetes and components of the metabolic syndrome, an association that remains even when controlling for known risk factors. Supporting preclinical work also suggests a causal role for AVP in metabolic dysfunction. It is known that individuals who habitually drink less fluids tend to have higher circulating AVP, which may be lowered by increasing water intake. In the short term, water supplementation in habitual low drinkers with high copeptin may reduce fasting glucose or glucagon, generating a proof of concept for the role of water supplementation in reducing incident metabolic disease. A large randomized trial is ongoing to determine whether water supplementation for 1 year in subjects with low water intake can meaningfully reduce fasting glucose, risk of new-onset diabetes, and other cardiometabolic risk factors., (© 2021 The Author(s) Published by S. Karger AG, Basel.)

Up to 50% of the adult population fail to meet the recommended total water intake despite the adverse health outcomes associated with chronic low fluid intake. Total fluid intake plays an important role in the energy and nutrient intake of individuals. Dietitians' role is to advise and guide the population toward a healthier diet. However, based on existing evidence, dietitians' current knowledge and practices regarding healthy hydration is an area for improvement. The European Healthy Hydration Awareness Campaign (EuHHAC) is an initiative between the European Federation of the Associations of Dietitians (EFAD) and the Hydration and Health Department of Danone Research, which aims to increase knowledge and awareness of healthy hydration and provide dietitians with evidence-based resources to use in practice. Since 2016, a series of tasks were undertaken by the EuHHAC group targeting dietitians across Europe. These tasks included an online survey addressing gaps in hydration knowledge, a webinar providing information on the terminology and impact of hydration on health, an interactive session addressing facilitators and barriers to healthy hydration, and a tutorial summarizing key hydration information and take-home messages. Dietitians were actively engaged in each aspect. Based on the feedback received, awareness of hydration was increased among dietitians. To further enhance understanding, an online Hydration Resource Center, including the resources of EuHHAC, will be created and uploaded on the EFAD website. Once completed an evaluation study will be undertaken to assess the usefulness of the resources in practice. The deliverables will be cascaded across Europe and worldwide via social media, conferences, and publications., (© 2019 The Author(s) Published by S. Karger AG, Basel.)

In children, maintaining adequate fluid intake and hydration is important for physiological reasons and for the adoption of healthy, sustainable drinking habits. In the Liq.In7 cross-sectional surveys involving 6,469 children (4-17 years) from 13 countries, 60% of children did not meet the European Food Safety Authority (EFSA) adequate intake for water from fluids. Beyond fluid quantity, the quality of what children drink is important for health. In these surveys, the contribution of sugar-sweetened beverages and fruit juices to total fluid intake (TFI) in children exceeded that of water in 6 out of 13 countries. To assess the adequacy of children's fluid intake, urinary biomarkers of hydration such as urine osmolality, urine specific gravity, and urine color may be used. To date, while there are no widely accepted specific threshold values for urine concentration to define adequate hydration in children, the available literature suggests that many children have highly concentrated urine, indicating insufficient fluid intake. This is worrisome since studies have demonstrated a relationship between low fluid intake or insufficient hydration and cognitive performance in children. Furthermore, results of the Liq.In7 surveys showed that at school - where children spend a significant amount of time and require optimal cognitive performance - children drink only 14% of their TFI. Consequently, it is pertinent to better understand the barriers to drinking water at school and encourage the promotion of water intake through multicomponent interventions that combine educational, environmental, and behavioral aspects to support adequate hydration as well as optimal cognition in children., (© 2019 The Author(s) Published by S. Karger AG, Basel.)

Purpose: To describe total fluid intake (TFI) and types of fluid consumed in urban China by age, gender, regions and city socioeconomic status relative to the adequate intakes (AI) set by the Chinese Nutrition Society., Methods: In 2016, participants aged 4-9, 10-17 and 18-55 years were recruited via a door-to-door approach in 27 cities in China. In total, 2233 participants were included. The volumes and sources of TFI were collected using the Liq.In 7 record, assisted by a photographic booklet of standard fluid containers., Results: The mean daily TFI among children, adolescents and adults were 966, 1177 and 1387 mL, respectively. In each age group, TFI was significantly higher in male vs female (981 vs 949, 1240 vs 1113, 1442 vs 1332; mL). Approximately 45, 36 and 28% of children, adolescents and adults reached the AI. Although plain water was the highest contributor to TFI, the contribution of sugar sweetened beverages (SSB) was ranked in the top three together with water and milk and derivatives. Approximately 27, 48 and 47% of children, adolescents and adults consumed more than one serving of SSB per day, respectively., Conclusions: A relatively large proportion of participants did not drink enough to meet the AI in urban China. Many children, adolescents and adults consumed more than one serving of SSB per day. A majority of children, adolescents and adults in the study population do not meet both quantitative and qualitative fluid intake requirements, and signal socioeconomic disparities.

Purpose: This study aimed to identify and characterize patterns of fluid intake in children and adolescents from six countries: Argentina, Brazil, China, Indonesia, Mexico and Uruguay., Methods: Data on fluid intake volume and type amongst children (4-9 years; N = 1400) and adolescents (10-17 years; N = 1781) were collected using the validated 7-day fluid-specific record (Liq.In 7 record). To identify relatively distinct clusters of subjects based on eight fluid types (water, milk and its derivatives, hot beverages, sugar-sweetened beverages (SSB), 100% fruit juices, artificial/non-nutritive sweetened beverages, alcoholic beverages, other beverages), a cluster analysis (partitioning around k-medoids algorithm) was used. Clusters were then characterized according to their socio-demographics and lifestyle indicators., Results: The six interpretable clusters identified were: low drinkers-SSB (n 523), low drinkers-water and milk (n 615), medium mixed drinkers (n 914), high drinkers-SSB (n 513), high drinkers-water (n 352) and very high drinkers-water (n 264). Country of residence was the dominant characteristic, followed by socioeconomic level, in all six patterns., Conclusions: This analysis showed that consumption of water and SSB were the primary drivers of the clusters. In addition to country, socio-demographic and lifestyle factors played a role in determining the characteristics of each cluster. This information highlights the need to target interventions in particular populations aimed at changing fluid intake behavior and improving health in children and adolescents.

Background: Mean daily water intake from fluids (WATER-FL) has proven to be difficult to measure because of a range of nonvalidated data collection techniques. Few questionnaires have been validated to estimate WATER-FL against self-reported diaries or urinary hydration markers, which may limit their objectivity. Objectives: The goals of this investigation were 1 ) to assess the validity of a 7-d fluid record (7dFLR) to measure WATER-FL (WATER-FL-7dFLR) through comparison with WATER-FL as calculated by measuring deuterium oxide (D 2 O) disappearance (WATER-FL-D 2 O), and 2 ) to evaluate the reliability of the 7dFLR in measuring WATER-FL. Methods: Participants [ n = 96; 51% female; mean ± SD age: 41 ± 14 y; mean ± SD body mass index (in kg/m 2 ): 26.2 ± 5.1] completed body water turnover analysis over 3 consecutive weeks. They completed the 7dFLR and food diaries during weeks 2 and 4 of the observation. The records were entered into nutritional software to determine the water content of all foods and fluids consumed. WATER-FL-D 2 O was calculated from water turnover (via the D 2 O dilution method), minus water from food and metabolic water. The agreement between the 2 methods of determining WATER-FL were compared according to a Bland-Altman plot at week 2. The test-retest reliability of 7dFLR between weeks 2 and 4 was assessed via intraclass correlation (ICC). Results: The mean ± SD difference between WATER-FL-7dFLR and WATER-FL-D 2 O was -131 ± 845 mL/d. In addition, no bias was observed ( F [1,94] = 0.484; R 2 = 0.006; P = 0.488). When comparing WATER-FL-7dFLR from weeks 2 and 4, no significant difference (mean ± SD difference: 71 ± 75 mL/d; t [79] = 0.954; P = 0.343) and an ICC of 0.85 (95% CI: 0.77, 0.90) was observed. Conclusions: The main findings of this study were that the use of the 7dFLR is an effective and reliable method to estimate WATER-FL in adults. This style of questionnaire may be extremely helpful for collecting water intake data for large-scale epidemiologic studies., Competing Interests: Author disclosures: LTJ, CC-J, AM, and JDA, no conflicts of interest. ECJ has an active grant with Danone Research. FP is a scientific consultant for Danone Research. IG and LJ are employees of Danone Research. SAK is a scientific consultant for Quest Diagnostics and has active grants with Danone Research., (© 2017 American Society for Nutrition.)

Objective: We investigated the effect of three interventions to increase the plain water consumption of children with unhealthy drinking habits, with an innovative approach combining the three layers of Installation Theory: embodied competences, affordances and social regulation., Methods: 334 preschool children and their carers were allocated to three interventions: Control (control): no intervention, Information (info): online coaching sessions on water health benefits aiming at modifying embodied competences (knowledge), Information + Water Affordance (info + w): the same plus home delivery of small bottles of water. After three months, half of the info and info + w subjects were allocated to Social Regulation (+social) (on-line discussion forum) or no further intervention (-social). Intake of plain water and all other fluid types of the children were recorded by the carers 6 times over a year using an online 7-day fluid-specific dietary record., Results: Over 1 year, all groups significantly increased daily water consumption by 3.0-7.8 times (+118 to +222 mL). Info + w + social and Info-social generated the highest increase in plain water intake after one year compared to baseline, by 7.8 times (+216 mL) and 6.7 times (+222 mL) respectively; both significantly exceeded the control (3.0 times, +118 mL), whilst the effect of info + w-social (5.0 times, +158 mL) and info + social (5.3 times, +198 mL) did not differ from that of control. All groups saw a decrease of sweetened beverages intake, again with info + w + social generating the largest decrease (-27%; -172 mL). No changes in other fluids or total fluid intake were observed., Conclusions: Sustainable increased water consumption can be achieved in children with unhealthy drinking habits by influencing representations, changing material affordances, and providing social regulation. Combining the three provided the strongest effect as predicted by Installation Theory., (Copyright © 2017. Published by Elsevier Ltd.)

Background: Pregnant and breastfeeding women experience great changes in their total body water content and water dynamics. To support the accretion of total body water during pregnancy and compensate for the water lost through breast milk during breastfeeding, increased adequate intakes (AI) for total water have been established by various health authorities. Despite this widespread advice, several studies suggest that pregnant and breastfeeding women do not meet the AI for total water, suggesting the need to raise women's awareness on the importance of adequate water intake, particularly during pregnancy and breastfeeding, as well as to provide them with a simple means of monitoring their hydration on a day-to-day basis. A urine color (UC) scale recently has been validated for hydration monitoring in pregnant and breastfeeding women., Summary: We sought to develop a version of a tool based on the UC scale, using only images or illustrations, which could be understood by users of various nationalities and spoken languages. Pregnant and breastfeeding women (n = 1,275) from Brazil, Mexico, and Poland were shown 3 versions of the tool. Understanding, appreciation, simplicity and intent to use were evaluated using a questionnaire consisting of 26 items. Key Messages: Among the 3 versions tested, one tool emerged as the most highly understood (88% spontaneous understanding) and was highly appreciated by users (mean [SD]: 8.40 [2.20] out of 10). There were no differences between countries. Furthermore, 83% reported being very likely to use the tool daily. These results suggest that a simple tool based on the UC scale will help pregnant and breastfeeding women meet the AI for total water., (© 2017 The Author(s) Published by S. Karger AG, Basel.)

Background: Ingestion of water has been associated with general wellbeing. When water intake is insufficient, symptoms such as thirst, fatigue and impaired memory result. Currently there are no instruments to assess water consumption associated with wellbeing. The objective of our study was to develop and validate such an instrument in urban, low socioeconomic, adult Mexican population., Methods: To construct the Water Ingestion-Related Wellbeing Instrument (WIRWI), a qualitative study in which wellbeing related to everyday practices and experiences in water consumption were investigated. To validate the WIRWI a formal, five-process procedure was used. Face and content validation were addressed, consistency was assessed by exploratory and confirmatory psychometric factor analyses, repeatability, reproducibility and concurrent validity were assessed by conducting correlation tests with other measures of wellbeing such as a quality of life instrument, the SF-36, and objective parameters such as urine osmolality, 24-hour urine total volume and others., Results: The final WIRWI is composed of 17 items assessing physical and mental dimensions. Items were selected based on their content and face validity. Exploratory and confirmatory factor analyses yielded Cronbach's alpha of 0.87 and 0.86, respectively. The final confirmatory factor analysis demonstrated that the model estimates were satisfactory for the constructs. Statistically significant correlations with the SF-36, total liquid consumption and simple water consumption were observed., Conclusion: The resulting WIRWI is a reliable tool for assessing wellbeing associated with consumption of plain water in Mexican adults and could be useful for similar groups.

In the last decade, cross-sectional and multiple cohort studies have associated total fluid intake or water intake with the risk for chronic kidney disease (CKD) and even the risk of developing hyperglycemia. Urine biomarkers have also been linked to the risk of CKD and lithiasis, and these biomarkers respond quickly to variations in fluid intake. High circulating copeptin levels, a surrogate marker of arginine vasopressin, have been associated with metabolic syndrome, renal dysfunction and increased risk for diabetes mellitus, cardiovascular disease and death. The aim of this paper was to explore how the various findings on water intake, hydration and health are interconnected, to highlight current gaps in our understanding and to propose a model that links water intake, homeostatic mechanisms to maintain water balance and health outcomes. Since plasma copeptin and vasopressin have been demonstrated to be sensitive to changes in water intake, inversely associated with 24-hour urine volume, and associated with urine biomarkers and fluid intake, vasopressin is proposed as the central player in this theoretical physiological model., (© 2016 The Author(s) Published by S. Karger AG, Basel.)

Purpose: To describe the intake of water and all other beverages in children and adolescents in 13 countries of three continents., Methods: Data of 3611 children (4-9 years) and 8109 adolescents (10-17 years) were retrieved from 13 cross-sectional surveys (47 % males). In three countries, stratified cluster sampling design was applied to randomly recruit schools classes. A quota method was applied in the other countries to randomly recruit participants. Details on the intake of all fluid types were obtained with a fluid-specific record over 7 consecutive days., Results: In the total sample, the highest mean intakes were observed for water (738 ± 567 mL/day), followed by milk (212 ± 209 mL/day), regular soft beverages (RSB) (168 ± 290 mL/day) and juices (128 ± 228 mL/day). Patterns characterized by a high contribution of water, RSB or hot beverages to total fluid intake were identified among the countries with close geographical location. Adolescents had a significantly lower milk intake and higher intake of RSB and hot beverages than children in most countries. The most consistent gender difference observed was that in both age groups males reported a significantly higher RSB consumption than females., Conclusion: On average, water was the fluid consumed in the largest volume by children and adolescents, but the intake of the different fluid types varied substantially between countries. Since the RSB intake was as large, or even larger, than water intake in some countries, undertaking actions to improve fluid intake habits of children and adolescents are warranted.

Purpose: To describe the intake of water and all other fluids and to evaluate the proportion of adults exceeding the World Health Organisation (WHO) recommendations on energy intake from free sugar, solely from fluids., Methods: A total of 16,276 adults (46 % men, mean age 39.8 years) were recruited in 13 countries from 3 continents. A 24-h fluid-specific record over 7 days was used for fluid assessment., Results: In Spain, France, Turkey, Iran, Indonesia and China, fluid intake was characterised by a high contribution of water (47-78 %) to total fluid intake (TFI), with a mean water intake between 0.76 and 1.78 L/day, and a mean energy intake from fluids from 182 to 428 kcal/day. Between 11 and 49 % of adults exceeded the free sugar WHO recommendations, considering solely fluids. In Germany, UK, Poland and Japan, the largest contributors to TFI were hot beverages (28-50 %) and water (18-32 %). Mean energy intake from fluids ranged from 415 to 817 kcal/day, and 48-62 % of adults exceeded free sugar WHO recommendations. In Mexico, Brazil and Argentina, the contribution of juices and regular sugar beverages (28-41 %) was as important as the water contribution to TFI (17-39 %). Mean energy intake from fluids ranged 565-694 kcal/day, and 60-66 % of the adults exceeded the free sugar WHO recommendation., Conclusions: The highest volumes recorded in most of the countries were for water, mean energy intake from fluids was up to 694 kcal/day, and 66 % of adults exceeded the free sugar WHO recommendation solely by fluids. Actions to create an environment in favour of water consumption and reduce sugar intake from fluids therefore are warranted.

Objective: To evaluate the effects of a change in water intake on mood and sensation in 22 habitual high-volume (HIGH; 2-4 L/d) and 30 low-volume (LOW; <1.2 L/d) drinkers who were asked to respectively decrease and increase their daily water intake., Method: During baseline HIGH consumed 2.5 L and LOW 1 L of water/day. During 3 controlled intervention days HIGH's water intake was restricted to 1 L/day whereas LOW's was increased to 2.5 L water/day. Several mood scales (Bond & Lader Visual Analog Scale (VAS), Profile of Mood States, Karolinska Sleepiness Scale, Thirst & Emotional VAS) were administered at different time points during the study. ANOVA including intervention, time point and intervention by time point as fixed effects on mean values (i.e.; baseline data vs. mean of 3 intervention days) for each mood scale was performed., Results: At baseline HIGH and LOW were comparable in mood state, except for thirst scores (estimate = 17.16, p<0.001) and POMS depression-dejection scores (estimate = 0.55, p<0.05) which were both higher in the HIGH vs. LOW. In HIGH the restricted water intake resulted in a significant increase in thirst (p<0.001) and a decrease in contentedness (p<0.05), calmness (p<0.01), positive emotions (p<0.05) and vigor/activity (p<0.001). In LOW, increased water consumption resulted in a significant decrease in fatigue/inertia (p<0.001), confusion/bewilderment (p = 0.05) and thirst (p<0.001) and a trend to lower sleepiness (p = 0.07) compared to baseline., Conclusion: Increasing water intake has beneficial effects in LOW, especially sleep/wake feelings, whereas decreasing water intake has detrimental effects on HIGH's mood. These deleterious effects in HIGH were observed in some sleep/wake moods as well as calmness, satisfaction and positive emotions.

Background/objectives: In sedentary adults, hydration is mostly influenced by total fluid intake and not by sweat losses; moreover, low daily fluid intake is associated with adverse health outcomes. This study aimed to model the relation between total fluid intake and urinary hydration biomarkers., Subjects/methods: During 4 consecutive weekdays, 82 adults (age, 31.6±4.3 years; body mass index, 23.2±2.7 kg/m(2); 52% female) recorded food and fluid consumed, collected one first morning urine (FMU) void and three 24-h (24hU) samples. The strength of linear association between urinary hydration biomarkers and fluid intake volume was evaluated using simple linear regression and Pearson's correlation. Multivariate partial least squares (PLS) modeled the association between fluid intake and 24hU hydration biomarkers., Results: Strong associations (|r| &#8805; 0.6; P<0.001) were found between total fluid intake volume and 24hU osmolality, color, specific gravity (USG), volume and solute concentrations. Many 24hU biomarkers were collinear (osmolality versus color: r=0.49-0.76; USG versus color: r=0.46-0.78; osmolality versus USG: 0.86-0.97; P<0.001). Measures in FMU were not strongly correlated to intake. Multivariate PLS and simple linear regression using urine volume explained >50% of the variance in fluid intake volume (r(2)=0.59 and 0.52, respectively); however the error in both models was high and the limits of agreement very large., Conclusions: Hydration biomarkers in 24hU are strongly correlated with daily total fluid intake volume in sedentary adults in free-living conditions; however, the margin of error in the present models limits the applicability of estimating fluid intake from urinary biomarkers.

Objective: The objective of the present study was to evaluate the effects of drinking 2 additional litres of water/day on several urinary risk factors for lithiasis in healthy subjects, through measurement of crystallization risk indices (Tiselius CRI)., Materials and Methods: 48 healthy subjects, aged 25 to 50 were studied for urinary parameters including CRI in the laboratory ward, for 24 hours. After this first period, they were randomized either to a 2L/d additional water intake (treated group) or usual fluid consumption (control group) for a 6 days period, which ended by a second measurement period in the laboratory ward for 24 hours., Results: Total additional water intake was actually 1.3L/d on average in treated subjects, because subjects decreased other usual sources of fluid intake. In 24 hour urine, Tiselius CRI varied differently among treated subjects and controls between the 2 periods; male controls subjects experienced much higher values (above 2 in average in first morning urine sample) in the second period (p = 0.05). Of interest, in a transversal analysis, we observed a positive relation between BMI or waist circumference on the one hand, and with 24 hour urea excretion or osmotic load on the other hand., Conclusion: These results show a beneficial effect of a final 1.3L additional water intake on Tiselius CRI in healthy subjects.