Urine color as an indicator of urine concentration in pregnant and lactating women

The applicability of the urine color scale in pediatric urology

AIMS

To determine the level of agreement between healthcare professionals, patients and their parents/guardians in the interpretation of the urine color scale (UCS) in cases of urinary dysfunction, analyzing the applicability of the scale as a diagnostic tool determining the hydration status.

METHODS

This was a cross-sectional study involving 5-17-year-old patients with lower urinary tract symptoms (LUTS) and enuresis. The study was conducted in a public healthcare referral center for pediatric urology in the Brazilian state of Bahia between October 2019 and March 2020. The Kolmogorov-Smirnov test was used to assess the distribution of the variables. Agreement was assessed using the kappa coefficient and weighted kappa. The z-test was used to determine significant differences between the kappa and weighted kappa. The statistical analysis was conducted using SPSS, version 14, and significance was established at p < 0.05.

RESULTS

Forty-four patients were included. The kappa value was 32.4% (p = 0.000) for the agreement between healthcare professionals and patients, 41.9% (p = 0.000) for agreement between healthcare professionals and parents/guardians, and 25.0% (p = 0.001) for agreement between patients and parents/guardians. The weighted kappa was 70.6% (p = 0.000) for agreement between healthcare professionals and patients, 82.4% (p = 0.000) for agreement between healthcare professionals and parents/guardians, and 51.5% (p = 0.001) for agreement between patients and parents/guardians. There was a statistically significant difference in kappa values when the healthcare professionals were compared with the other groups.

CONCLUSIONS

Although there were some inconsistencies in interpretation, the UCS proved to be a useful tool with which to evaluate patients' hydration status.

Assessment of urine colour using a wallet card: a randomised study of a novel patient self-care tool during chemoradiation for oesophageal cancer

BACKGROUND

Patients undergoing neoadjuvant chemoradiation for oesophageal cancer often experience dehydration from decreased fluid intake and increased losses. Despite frequent clinical visits during treatment, patients can still present with dehydration, suggesting the need for increased patient awareness and engagement around adverse event management at home. Evidence for benefits of self-monitoring may help motivate patients to engage proactively in their own care to improve their treatment experience.

METHODS

We performed a randomised single-centre study of a urine colour self-monitoring card (UCC) during chemoradiation therapy for oesophageal cancer, compared with standard dietitian counselling. Primary outcome was self-efficacy as determined by the Self-Management Resource Centre Self-Efficacy for Managing Chronic Disease Scale (SMCD). Secondary outcomes included Burge thirst scores, Edmonton Symptom Assessment System scores (ESAS), patient-initiated hydrations, creatinine rise and satisfaction with the UCC.

RESULTS

Thirty-five patients were randomised. UCC use was not associated with improved SMCD or ESAS scores compared with standard counselling. The card was highly rated by patients as a welcome tool for self-monitoring.

CONCLUSIONS

No beneficial effect on self-efficacy or dehydration markers with UCC use was demonstrated. The study nonetheless drew attention to several factors potentially hindering its use for effective self-care: the unexpected severity of other symptoms consuming patients' attention, reduced sensitivity of urine colour due to chemotherapy, absence of active inquiry by the healthcare team and the inconvenient location of the UCC in wallet/purse. Urine colour monitoring in patients with oesophageal cancer to improve the patient experience during treatment warrants further study but supported by active healthcare provider inquiry, more accessible format of the card, and possibly home vital checks to increase its sensitivity in the clinical context.

Analysis on fluid intake and urination behaviors among the elderly in five cities in China: a cross-sectional study

Background

Fluid intake in the elderly may influence urination behaviors and further influence their health status. This study investigated the behaviors of fluid intake, urination and their relationships among the elderly in China.

Methods

Stratified random sampling was used to recruit the elderly participants who met the inclusion criteria from five cities in China. Participants' total fluid intake (TFI) level was investigated using a validated 7-day 24 h fluid intake questionnaire. Their urination behaviors in real time were also recorded using a validated 7-day 24 h urination behavior record.

Results

A total of 524 participants completed the study, including 233 males and 291 females. The average age was 69.7 years. The median daily TFI was 1,241 mL, with a frequency of 8.1 times per day. Approximately 73.3% of the participants did not reach the amount of adequate fluid intake (1.7 L for males and 1.5 L for females) recommended in China. Fluid intake in the morning, afternoon, and evening among participants was 594 mL, 305 mL and 342 mL, with a frequency of 3.0 times, 1.7 times, and 2.0 times, respectively. The median urination frequency was 7.4 times per day. The percentage of participants who urinated >7 times during the day was 44.3%. The percentage of participants who urinated ≥1 time at night was 77.5%. Age and BMI were not the main influence factors for fluid intake and urination behaviors. The preliminary analysis showed that higher TFI, plain water intake, dairy products intake, and fluid intake frequency were significantly associated with higher urination frequency (t = 6.553, p < 0.05; t = 5.291, p < 0.05; t = 4.667, p < 0.05; t = 13.413, p < 0.05). Higher fluid intake per time was significantly associated with lower urination frequency (t = -3.562, p < 0.05). Correlations between TFI, fluid intake frequency, fluid intake in night, fluid intake frequency in night and urination at night were also found (r = 0.114, p < 0.05; r = 0.091, p < 0.05; r = 0.146, p < 0.05; r = 0.331, p < 0.05).

Conclusion

Fluid intake was inadequate in terms of the elderly participants. Participants with higher fluid intake and frequency in night had a greater incidence of nocturia. Thus, correcting fluid intake behaviors can improve urination behavior and promote health.

Clinical trial registration

https://www.chictr.org.cn/searchprojEN.html, identifier CTR1900023355.

Household Water Is the Main Source of Iodine Consumption among Women in Hargeisa, Somaliland: A Cross-Sectional Study

BACKGROUND

Iodine status surveys of women in Somaliland present widely conflicting results. Previous research indicates elevated concentrations of iodine (IQR 18-72 μg/L) in groundwater used for drinking and cooking, but the relation with iodine intake is not well characterized.

OBJECTIVES

We aimed to investigate the contributions of household water iodine concentration (WIC), breastfeeding, total fluid intake, hydration levels, and urine volume on urinary iodine concentration (UIC) and excretion (UIE) over a 24-h period and to define iodine status from iodine intake estimates and median UIC, normalized to a mean urine volume of 1.38 L/d (hydration adjusted).

METHODS

The study sample comprised 118 nonpregnant, healthy women aged 15-69 y. All participants resided in Hargeisa, and 27 were breastfeeding. Data collection consisted of a 24-h urine collection, a 24-h fluid intake diary, a beverage frequency questionnaire, and a structured recall interview. We measured UIC and WIC in all urine and in 49 household water samples using the Sandell-Kolthoff reaction.

RESULTS

WIC ranged between 3 and 188 μg/L, with significant median differences across the water sources and city districts (P < 0.003). Nonbreastfeeding women were borderline iodine sufficient [hydration-adjusted median urinary iodine concentration (mUIC) 109 μg/L; 95% CI: 97, 121 μg/L], whereas breastfeeding women showed a mild iodine deficiency (73 μg/L; 95% CI: 54, 90 μg/L). There were strong correlations (ρ: 0.50-0.69, P = 0.001) between WIC and UIC, with iodine from household water contributing more than one-half of the total iodine intake. Multivariate regression showed hydration and breastfeeding status to be the main predictors of UIC.

CONCLUSIONS

Iodine from household water is the main contributor to total iodine intake among women in Hargeisa, Somaliland. Variation in female hydration and spatial and temporal WIC may explain diverging mUIC between studies. Water sources at the extremes of low and high iodine concentrations increase the risk of subpopulations with insufficient or more than adequate iodine intake.

Variation in urine osmolality throughout pregnancy: a longitudinal, randomized-control trial among women with overweight and obesity

PURPOSE

Water needs increase during pregnancy, and proper hydration is critical for maternal and fetal health. This study characterized weekly hydration status changes throughout pregnancy and examined change in response to a randomized, behavioral intervention. An exploratory analysis tested how underhydration during pregnancy was associated with birth outcomes.

METHODS

The Healthy Mom Zone Study is a longitudinal, randomized-control trial intervention aiming to regulate gestational weight gain (GWG) in pregnant women with overweight/obesity (n = 27). Fourteen women received standard of care; 13 women additionally received weekly guidance on nutrition, physical activity, water intake, and health-promoting behaviors. Hydration status was measured weekly via overnight urine osmolality (Uosm) from ~ 8-36 weeks gestation; underhydration was dichotomized (Uosm ≥ 500 mOsm/kg). Gestational age- and sex-standardized birth weight and length z scores and percentiles were calculated. We used mixed-effect and linear regression models to test covariate-adjusted relationships.

RESULTS

No differences existed in Uosm or other characteristics between control and intervention women at baseline. Significant interactions (p = 0.01) between intervention and week of pregnancy on Uosm indicated intervention women maintained lower Uosm, whereas control women had a significant quadratic (inverse-U) relationship and greater Uosm in the second and early third trimesters. Results were consistent across robustness and sensitivity checks. Exploratory analyses suggest underhydration was associated with birth weight, but not length, in opposite ways in the second vs. third trimester.

CONCLUSION

A multi-component behavioral intervention helped women with overweight/obesity maintain better hydration throughout pregnancy. Future studies should confirm birth outcome results as they have important implications for early life nutrition.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03945266; registered May 10, 2019 retrospectively.

The Relationships between Water Intake and Hydration Biomarkers and the Applications for Assessing Adequate Total Water Intake among Young Adults in Hebei, China

Water is an essential nutrient for humans. A cross-sectional study was conducted among 159 young adults aged 18–23 years in Hebei, China. The total drinking fluids and water from food were obtained by 7-day 24 h fluid intake questionnaires and the duplicate portion method, respectively. Pearson’s correlation coefficients were performed to determine the relationship between fluid intake and 24 h urinary biomarkers and plasma biomarkers. A multivariable partial least squares (PLS) model was used to identify the key predictors in modeling the total water intake (TWI) with 24 h urine biomarkers. Logistic regressions of the TWI against binary variables were performed, and the receiver operating characteristic curve (ROC) was analyzed to determine the cutoff value of the TWI for the optimal hydration status and dehydration without adjustments to favor either the sensitivity or specificity. In total, 156 participants (80 males and 76 females) completed the study. Strong relationships were found between the total drinking fluids, TWI, and 24 h urine biomarkers among young adults, especially for the 24 h urine volume (r = 0.784, p < 0.001; r = 0.747, p < 0.001) and osmolality (r = −0.589, p < 0.001; r = −0.477, p < 0.001), respectively. As for the FMU and plasma biomarkers, no strong relationships were found. The percentages of the variance in TWI explained by the PLS model with 13 urinary biomarkers were 66.9%. The optimal TWI values for assessing the optimal hydration and dehydration were 2892 mL and 2482 mL for young males, respectively, and 2139 mL and 1507 mL for young females, respectively. Strong relationships were found between the TWI, total drinking fluids, and 24 h urine biomarkers, but not with the FMU and plasma biomarkers, among young adults, including males and females. The 24 h urine biomarkers were more sensitive than the first morning urinary biomarkers in reflecting the fluid intake. The TWI was a reliable index for assessing the hydration statuses for young adults in free-living conditions.

Estimates of fluid intake, urine output and hydration-levels in women from Somaliland: a cross-sectional study

The study objective was to measure fluid intake and associations with background characteristics and hydration biomarkers in healthy, free-living, non-pregnant women aged 15–69 years from Hargeisa city. We also wanted to estimate the proportion of euhydrated participants and corresponding biomarker cut-off values. Data from 136 women, collected through diaries and questionnaires, 24h urine samples and anthropometric measurements, were obtained with a cross-sectional, purposeful sampling from fifty-two school and health clusters, representing approximately 2250 women. The mean (95 % CI) 24 h total fluid intake (TFI) for all women was 2⋅04 (1⋅88, 2⋅20) litres. In multivariate regression with weight, age, parity and a chronic health problem, only weight remained a predictor (P 0.034, B 0.0156 (l/kg)). Pure water, Somali tea and juice from powder and syrup represented 49⋅3, 24⋅6 and 11⋅7 % of TFI throughout the year, respectively. Mean (95 % CI) 24 h urine volume (Uvol) was 1⋅28 (1⋅17, 1⋅39) litres. TFI correlated strongly with 24 h urine units (r 0.67) and Uvol (r 0.59). Approximately 40 % of the women showed inadequate hydration, using a threshold of urine specific gravity (Usg) of 1⋅013 and urine colour (Ucol) of 4. Five percent had Usg > 1⋅020 and concomitant Ucol > 6, indicating dehydration. TFI lower cut-offs for euhydrated, non-breast-feeding women were 1⋅77 litres and for breast-feeding, 2⋅13 litres. Euhydration cut-off for Uvol was 0⋅95 litre, equalling 9⋅2 urine units. With the knowledge of adverse health effects of habitual hypohydration, Somaliland women should be encouraged to a higher fluid intake.

Effect of dehydration during pregnancy on birth weight and length in West Jakarta

Nutrition and maternal behavior are critical factors in fetal development. Maternal water intake is necessary to regulate metabolism and may influence fetal growth. This study aims to determine the effect of dehydration during pregnancy on birth weight and length. This cohort-prospective study took place in the area of Kebon Jeruk District Health Centre. A total of 38 subjects of pregnant women in their second trimester were examined. Subject characteristics were collected through direct measurements and interviews. Urine and blood samples were collected at the sixth trimester (32-34 and 35-37 weeks) to determine hydration status. Nutritional status was collected through food recall, while birth weight and length were obtained from the anthropometric measurements 30 min after birth. From a total of 38 subjects, 20 were dehydrated, and 18 were well hydrated. There was a significant relationship between hydration status and water intake, birth weight and length, head circumference, and chest circumference. After being corrected to the level of water intake, the difference in birth weight and length between the two groups were 500⋅6 g and 0⋅4 cm, and 0⋅8 cm and 1⋅4 cm for the head circumference and chest circumference (P < 0⋅05). It is recommended for mothers to monitor their weight and ensure fluid intake of 3⋅0 l per day. Further research requires more subjects to observe the effects of chronic maternal dehydration on pregnancy output and a cohort study that monitors infant development in the first six months of life.

Combining urine color and void number to assess hydration in adults and children

BACKGROUND/OBJECTIVES

To test the diagnostic ability of two combined practical markers for elevated urine osmolality (underhydration) in free-living adults and children.

SUBJECTS/METHODS

One hundred and one healthy adults (females n = 52, 40 ± 14 y, 1.70 ± 0.95 m, 76.7 ± 17.4 kg, 26.5 ± 5.5 kg/m²) and 210 children (females = 105, 1.49 ± 0.13 m, 43.4 ± 12.6 kg, 19.2 ± 3.2 kg m^-2) collected urine for 24-h. Urine was analyzed for urine osmolality (UOsm), color (UC), while the number of voids (void) was also recorded. Receiver Operating Characteristic (ROC) analysis was performed for UC, void, and combination of UC and void, to determine markers' diagnostic ability for detecting underhydration based on elevated UOsm (UOsm ≥ 800 mmol kg^-1).

RESULTS

Linear regression analysis revealed that UC was significantly associated with UOsm in both adults (R² = 0.38; P < 0.001) and children (R² = 0.45; P < 0.001). Void was significantly associated with UOsm in both adults (R² = 0.13; P < 0.001) and children (R² = 0.15; P < 0.001). In adults, when UC > 3 and void <7 were combined, the overall diagnostic ability for underhydration was 97% with sensitivity and specificity of 100% and 88%, respectively. In children, UC > 3 and void <5 had an overall diagnostic ability for underhydration of 89% with sensitivity and specificity of 100% and 62%, respectively.

CONCLUSIONS

Urine color alone and the combination of urine color with void number can a valid and simple field-measure to detect underhydration based on elevated urine osmolality.

A lavatory urine color (LUC) chart method can identify hypohydration in a physically active population

PURPOSE

To provide a new and efficient at-the-toilet-bowl method of self-assessing urine concentration via urine color (Uc) to identify hypohydration.

METHODS

A large athletic population (n = 189) delivered a urine sample, then chose a color panel that was displayed on the back wall of the lavatory stall. Selection was based on duration of urine voiding time, so that for a short-duration, the lighter panel was selected; for a mid-duration, the mid color panel; and for a longer-void-duration, the darker panel was selected. Then, subjects noted if their urine was lighter than, similar to, or darker than the selected color panel. Trained investigators also rated subjects' urine samples. To assess validity of Uc classification, the outcome was compared with a urine concentration (urine specific gravity, USG, and urine osmolality) threshold indicating hypohydration.

RESULTS

Urine color was scored similarly by subjects and investigators (P = 0.99). Based on receiver operating curves (ROC), the method scored fair, i.e., the area under the curve ranging 0.73-0.82, with an accuracy of participants and investigators correctly classifying 72% and 75% urine samples compared to a USG threshold of 1.020, respectively, and 62% and 70% compared to a urine osmolality threshold of 836 mmol·kg^-1, respectively.

CONCLUSION

This new lavatory urine color (LUC) method of scoring Uc levels to assess potential hypohydration gives results similar to those of traditional urine color charts, but it has the advantage of an immediate assessment of hydration status based on scoring urine color directly from the toilet bowl.

The comparison of water intake patterns and hydration biomarkers among young adults with different hydration statuses in Hebei, China

Background

Water is essential for maintaining the functions of human body properly. Studies have shown that the amounts and contributions of fluids were associated with health and hydration status. The objectives of the study was that to explore the differences of water intake pattern and hydration biomarkers among young males and females in different hydration statuses.

Methods

A cross-sectional study was implemented among 159 young adults aged 18–23 years in Hebei, China. The total drinking fluids and water from food were obtained by 7-day 24-h fluid intake questionnaire and duplicate portion method, respectively. The osmolality and electrolyte concentrations of the 24 h urine and plasma were tested. Differences in optimal hydration (OH), middle hydration (MH) and hypohydration (HH) groups, divided by the osmolality of 24 h urine, were compared.

Results

Totally, 156 participants (80 males and 76 females) completed the study. OH group had highest proportions of participants met the recommendations of total water intake (TWI) and total drinking fluids of China (34.5%, 36.2%), while HH group had lowest (7.7%, 0.0%). OH group had higher amounts of TWI, total drinking fluids, water and lower amounts of sugar-sweetened-beverages (SSBs) (P < 0.05). The percentage of total drinking fluids in TWI decreased from 54.1% in OH group to 42.6% in HH group (P < 0.05). OH group had higher and lower contributions of water and SSBs to total drinking fluids (P < 0.05); produced 551–950 mL more, excreted significantly less quantity of solutes of urine (P < 0.05). No significant differences were found in plasma osmolality among the three groups (P > 0.05). Among both males and females, the amounts of TWI and water were higher in OH group than others (P < 0.05). Males had 4.3% lower, 5.4% and 1.1% higher contributions of milk and milk products, SSBs and alcohol to total drinking fluids than females (P < 0.05); males had higher volume of urine than females only in MH group (P < 0.05). There were no significant differences of plasma osmolality between males and females in the same group (P > 0.05).

Conclusions

Young adults with optimal hydration status had better water intake pattern and less concentrated urine. Females maybe have better water intake pattern than males.

Trial registration Chinese clinical trial registry. Name of the registry: Relationship of drinking water and urination. Trial registration number: ChiCTR-ROC-17010320. Date of registration: 01/04/2017. URL of trial registry record: http://www.chictr.org.cn/edit.aspx?pid=17601&htm=4.

Insulin-regulated aminopeptidase deficiency impairs cardiovascular adaptations and placental development during pregnancy

Insulin-regulated aminopeptidase (IRAP), an enzyme that cleaves vasoactive peptides including oxytocin and vasopressin, is suggested to play a role in pregnancy and the onset of preeclampsia. Our aim was to examine the contribution of IRAP to arterial pressure regulation and placental development during pregnancy in mice. Mean arterial pressure and heart rate were measured via radiotelemetry in 12-week-old female wild-type and IRAP knockout mice. Females were time-mated with males of the same genotype. Placentae were collected at embryonic day 18.5 for histological analysis. Basal heart rate was ∼40 bpm lower in IRAP knockout females compared with wild-type females. The increase in heart rate across gestation was greater in IRAP knockout females than wild-type females. Neither basal nor gestational mean arterial pressure was different between wildtype and IRAP knockout females. Urine output and water intake of IRAP knockout mice were ∼45% less than wild-type mice at late gestation. IRAP deficiency had no effect on fetal weight. Morphological assessment of placentae revealed that IRAP deficiency was associated with reduced labyrinth surface area and accumulation of glycogen in the junctional zone. Our data demonstrate that IRAP deficiency alters maternal fluid handling and impairs placental labyrinth expansion at late gestation, indicating that IRAP contributes to the normal adaptions to pregnancy.

Hydration for health hypothesis: a narrative review of supporting evidence

PURPOSE

An increasing body of evidence suggests that excreting a generous volume of diluted urine is associated with short- and long-term beneficial health effects, especially for kidney and metabolic function. However, water intake and hydration remain under-investigated and optimal hydration is poorly and inconsistently defined. This review tests the hypothesis that optimal chronic water intake positively impacts various aspects of health and proposes an evidence-based definition of optimal hydration.

METHODS

Search strategy included PubMed and Google Scholar using relevant keywords for each health outcome, complemented by manual search of article reference lists and the expertise of relevant practitioners for each area studied.

RESULTS

The available literature suggest the effects of increased water intake on health may be direct, due to increased urine flow or urine dilution, or indirect, mediated by a reduction in osmotically -stimulated vasopressin (AVP). Urine flow affects the formation of kidney stones and recurrence of urinary tract infection, while increased circulating AVP is implicated in metabolic disease, chronic kidney disease, and autosomal dominant polycystic kidney disease.

CONCLUSION

In order to ensure optimal hydration, it is proposed that optimal total water intake should approach 2.5 to 3.5 L day^-1 to allow for the daily excretion of 2 to 3 L of dilute (< 500 mOsm kg^-1) urine. Simple urinary markers of hydration such as urine color or void frequency may be used to monitor and adjust intake.

Measuring Human Water Needs

Water connects the environment, culture, and biology, yet only recently has it emerged as a major focus for research in human biology. To facilitate such research, we describe methods to measure biological, environmental, and perceptual indicators of human water needs. This toolkit provides an overview of methods for assessing different dimensions of human water need, both well‐established and newly‐developed. These include: (a) markers of hydration (eg, urine specific gravity, doubly labeled water) important for measuring the impacts of water need on human biological functioning; (b) methods for measuring water quality (eg, digital colorimeter, membrane filtration) essential for understanding the health risks associated with exposure to microbiological, organic, metal, inorganic nonmental, and other contaminants; and (c) assessments of household water insecurity status that track aspects of unmet water needs (eg, inadequate water service, unaffordability, and experiences of water insecurity) that are directly relevant to human health and biology. Together, these methods can advance new research about the role of water in human biology and health, including the ways that insufficient, unsafe, or insecure water produces negative biological and health outcomes.

Association between total water intake and dietary intake of pregnant and breastfeeding women in China: a cross-sectional survey

BACKGROUND

Pregnant and lactating women are at high risk of insufficient water intake. The cross-sectional study was mainly designed to evaluate the water intake, including total water intake (TWI), plain water intake, and water intake from beverages and foods of 200 pregnant women and 150 breastfeeding women in Beijing.

METHODS

A semi-quantitative Food Frequency Questionnaire (FFQ) was employed to assess their dietary intake, TWI, plain water, and water intake from beverages and foods. Multivariate regression analysis was conducted for evaluating the association between water intake and dietary variables.

RESULTS

On average, the TWI of pregnant and breastfeeding women was 2638 mL/day and 3218 mL/day, respectively. Only 28% of pregnant women and 27% of breastfeeding women were complied with the adequate intake (AI). Water from foods was the greatest contributor to TWI both in pregnant and breastfeeding women. TWI was positively related to some dietary variables (P < 0.001). For pregnant women, with each 100 kcal/day increase in energy intake, the TWI increased by 67 mL. With each 5 g increase in daily intake of dietary protein, fat, carbohydrate and fiber, TWI increased by 72 mL, 66 mL, 22 mL, 353 mL, respectively. When the energy contribution of protein increased by 5%, TWI increased by 210 mL. The each 100 mg increase in daily sodium intake was accompanied with 52 mL increase in TWI. For breastfeeding women, with each 100 kcal/day increase in energy intake, the TWI increased by 54 mL. With each 5 g increase in daily intake of dietary protein, fat, carbohydrate and fiber, TWI increased by 53 mL, 58 mL, 16 mL, 212 mL, respectively. The each 100 mg increase in daily sodium intake was accompanied with 54 mL increase in TWI.

CONCLUSIONS

A large proportion of pregnant and breastfeeding women in Beijing were not adherent to AI for TWI set by Chinese Nutrition Society. Water intake from foods was the greatest contributor to TWI both in pregnant and breastfeeding women, and maternal dietary intake posed impacts on water intake during pregnancy and lactation. More researches are required to assess the water intake and hydration status of the populations.

Adaptation and Validation of the Hydration Status Questionnaire in a Spanish Adolescent-Young Population: A Cross Sectional Study

The achievement of adequate hydration status is essential for mental and physical performance and for health in general, especially in children and adolescents. Nevertheless, little is known about hydration status of this population, mainly due to the limited availability of research tools; thus, the objective of the current study was to adapt and validate our hydration status questionnaire in a Spanish adolescent-young population. The questionnaire was validated against important hydration markers: urine colour, urine specific gravity, haemoglobin, haematocrit and total body water and involved 128 subjects aged between 12⁻17 years. Water intake was also estimated through a three-day dietary record and physical activity was assessed through accelerometers. Participants completed the questionnaire twice. Water balance and water intake were correlated with urine specific gravity and with total body water content. Water intake obtained by the questionnaire was correlated with results from the three-day dietary record. The intraclass correlation coefficient indicated moderate concordance between both recordings and the Cronbach's alpha revealed high consistency. The Bland and Altman method indicated that the limits of agreement were acceptable to reveal the reliability of the estimated measures. In conclusion, this is the first time that a questionnaire is valid and reliable to estimate hydration status of adolescent-young populations.

Relationships between hydration biomarkers and total fluid intake in pregnant and lactating women

INTRODUCTION

Previous research established significant relationships between total fluid intake (TFI) and urinary biomarkers of the hydration process in free-living males and females; however, the nature of this relationship is not known for pregnant (PREG) and lactating (LACT) women.

PURPOSE

To determine the relationship between urinary and hematological hydration biomarkers with TFI in PREG and LACT.

METHODS

Eighteen PREG/LACT (age: 31 ± 3 years, pre-pregnancy BMI: 24.26 ± 5.85 kg m-2) collected 24-h urine samples, recorded TFI, and provided a blood sample at 5 time points (15 ± 2, 26 ± 1, 37 ± 1 weeks gestation, 3 ± 1 and 9 ± 1 weeks postpartum during lactation); 18 pair-matched non-pregnant (NP), non-lactating (NL) women (age: 29 ± 4 years, BMI: 24.1 ± 3.7 kg m-2) provided samples at similar time intervals. Twenty-four-hour urine volume (U VOL), osmolality (U OSM), specific gravity (U SG), and color (U COL) were measured. Hematocrit, serum osmolality (S OSM), and serum total protein (S TP) were measured in blood.

RESULTS

Significant relationships were present between TFI and urinary biomarkers in all women (P < 0.004); these relationships were not different between PREG and NP, and LACT and NL, except U VOL in PREG (P = 0.0017). No significant relationships between TFI and hematological biomarkers existed (P > 0.05).

CONCLUSION

Urinary biomarkers of hydration, but not hematological biomarkers, have a strong relationship with TFI in PREG, LACT, NP, and NL women. These data suggest that urinary biomarkers of hydration reflect TFI during pregnancy and breast-feeding.

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 (U_Osm) 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 U_Osm is not practical. In this analysis, we calculate criterion values for urine-specific gravity (U_SG) and urine color (U_Col), 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 U_SG ⩾1.013 detects U_Osm>500 mOsm/kg with very high accuracy (AUC 0.984), whereas a subject-assessed U_Col⩾4 offers high sensitivity and moderate specificity (AUC 0.831) for detecting U_Osm >500 m Osm/kg.

Fluid Intake of Pregnant and Breastfeeding Women in Indonesia: A Cross-Sectional Survey with a Seven-Day Fluid Specific Record

During pregnancy and lactation, the adequate intake (AI) for total water intake is increased. This cross-sectional survey aimed to assess Total Fluid Intake (TFI; sum of drinking water and all other fluids) of 300 pregnant and 300 breastfeeding women in Indonesia. A seven-day fluid specific record was used to assess TFI. Mean TFI of pregnant and breastfeeding women were 2332 ± 746 mL/day and 2525 ± 843 mL/day, respectively. No significant difference in TFI between pregnancy trimesters was observed, while TFI of women breastfeeding for 12–24 months postpartum (2427 ± 955 mL/day) was lower than that of the two other groups (0–5 months: 2607 ± 754 mL/day; 6–11 months: 2538 ± 807 mL/day, respectively). Forty-two and 54% of the pregnant and breastfeeding subjects, respectively, did not reach the AI of water from fluids. These AI were actually known by only 14% and 23% of the pregnant and breastfeeding subjects. However, having the knowledge about the AI did not increase the odds of reaching the AI. Concluding that a high proportion of the pregnant and breastfeeding subjects did not reach the AI of water from fluid, it seems pertinent to further assess the fluid intake, as well as their hydration status, in other countries.