Analysis of 2009⁻2012 Nutrition Health and Examination Survey (NHANES) Data to Estimate the Median Water Intake Associated with Meeting Hydration Criteria for Individuals Aged 12⁻80 in the US Population

Sufficient water intake maintains the gut microbiota and immune homeostasis and promotes pathogen elimination

Water is the most abundant substance in the human body and plays a pivotal role in various bodily functions. While underhydration is associated with the incidence of certain diseases, the specific role of water in gut function remains largely unexplored. Here, we show that water restriction disrupts gut homeostasis, which is accompanied by a bloom of gut microbes and decreased numbers of immune cells, especially Th17 cells, within the colon. These microbial and immunological changes in the gut are associated with an impaired ability to eliminate the enteric pathogen Citrobacter rodentium. Moreover, aquaporin 3, a water channel protein, is required for the maintenance of Th17 cell function and differentiation. Taken together, adequate water intake is critical for maintaining bacterial and immunological homeostasis in the gut, thereby enhancing host defenses against enteric pathogens.

Hypohydration attenuates increases in creatinine clearance to oral protein loading and the renal hemodynamic response to exercise pressor reflex

Insufficient hydration is prevalent among free living adults. This study investigated whether hypohydration alters 1) renal functional reserve, 2) the renal hemodynamic response to the exercise pressor reflex, and 3) urine-concentrating ability during oral protein loading. In a block-randomized crossover design, 22 healthy young adults (11 females and 11 males) underwent 24-h fluid deprivation (Hypohydrated) or 24-h normal fluid consumption (Euhydrated). Renal functional reserve was assessed by oral protein loading. Renal hemodynamics during the exercise pressor reflex were assessed via Doppler ultrasound. Urine-concentrating ability was assessed via free water clearance. Creatinine clearance did not differ at 150 min postprotein consumption between conditions [Hypohydrated: 246 mL/min, 95% confidence interval (CI): 212-280; Euhydrated: 231 mL/min, 95% CI: 196-265, P = 0.2691] despite an elevated baseline in Hypohydrated (261 mL/min, 95% CI: 218-303 vs. 143 mL/min, 95% CI: 118-168, P < 0.0001). Renal artery vascular resistance was not different at baseline (P = 0.9290), but increases were attenuated in Hypohydrated versus Euhydrated at the end of handgrip (0.5 mmHg/cm/s, 95% CI: 0.4-0.7 vs. 0.8 mmHg/cm/s 95% CI: 0.6-1.1, P = 0.0203) and end occlusion (0.2 mmHg/cm/s, 95% CI: 0.1-0.3 vs. 0.4 mmHg/cm/s 95% CI: 0.3-0.6, P = 0.0127). There were no differences between conditions in free water clearance at 150 min postprotein (P = 0.3489). These data indicate that hypohydration 1) engages renal functional reserve and attenuates the ability to further increase creatinine clearance, 2) attenuates increases in renal artery vascular resistance to the exercise pressor reflex, and 3) does not further enhance nor impair urine-concentrating ability during oral protein loading.NEW & NOTEWORTHY Insufficient hydration is prevalent among free living adults. This study found that hypohydration induced by 24-h fluid deprivation engaged renal functional reserve and that oral protein loading did not further increase creatinine clearance. Hypohydration also attenuated the ability to increase renal vascular resistance during the exercise pressor reflex. In addition, hypohydration neither enhanced nor impaired urine-concentrating ability during oral protein loading. These data support the importance of mitigating hypohydration in free living adults.

Self-perception of voice, hearing, and general health in screening for voice changes in older women

PURPOSE

To verify the association between sociodemographic factors, vocal behavior, morbidities, and self-perception of voice, hearing, and general health in older women with voice disorders.

METHODS

The sample had 95 older women aged 60 to 84 years (mean of 69,5). They were interviewed with a structured questionnaire on sociodemographic aspects, health, and vocal behavior. The Screening Protocol for Voice Disorders in Older Adults (RAVI) was used to identify the presence of voice disorders.

RESULTS

Participants who had finished high school and were retired predominated. The number of older women with voice disorders according to RAVI was 46.3%. Physical sensations such as dry throat, throat clearing, and itchy throat were the most common complaints. The group of older women with voice disorders had worse self-perception of voice quality, hearing, and general health and a higher frequency of upper airway infections than those without voice disorders (p ≤ 0.05).

CONCLUSION

The vocal self-assessment measured with RAVI was statistically associated with self-perception of voice quality, hearing, general health, sore throat, sinusitis, and respiratory allergies.

Water Intake and Handgrip Strength in US Adults: A Cross-Sectional Study Based on NHANES 2011-2014 Data

This study aimed to examine the relationship between daily total intake of water (DTIW) and handgrip strength (HGS) among US adults and to explore the impact of water intake on muscle function and health, providing a reference for public health policies and health education. Using the data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014, a cross-sectional survey design was adopted to analyze 5427 adults (48.37% female and 51.63% male) aged 20 years and above. DTIW was assessed using two non-consecutive 24 h dietary recall interviews, and the HGS level was measured using a Takei Dynamometer. Weighted generalized linear regression models and restricted cubic spline plots were used to analyze the linear and nonlinear associations between DTIW and HGS level and to conduct a gender subgroup analysis and an interaction effect test. The results showed that there were significant differences in HGS and other characteristics among different quartile groups of DTIW (p < 0.05). There was a significant nonlinear trend (exhibiting an inverted U-curve) between DTIW and HGS (p for nonlinear = 0.0044), with a cut-off point of 2663 g/day. Gender subgroup analysis showed that the nonlinear trend (exhibiting an inverted U-curve) was significant only in males (p for nonlinear = 0.0016), with a cut-off point of 2595 g/day. None of the stratified variables had an interaction effect on the association between DTIW and HGS (p for interaction > 0.05). In conclusion, this study found a nonlinear association between DTIW and HGS levels, as well as a gender difference. This finding provides new clues and directions for exploring the mechanism of the impact of DTIW on muscle function and health and also provides new evidence and suggestions for adults to adjust their water intake reasonably.

Does Self-Perceived Diet Quality Align with Nutrient Intake? A Cross-Sectional Study Using the Food Nutrient Index and Diet Quality Score

A reliable diet quality (DQ) assessment is critical to empower individuals to improve their dietary choices. Controversies persist as to whether self-perceived DQ is accurate and correlated with actual DQ as assessed by validated nutrient intake indexes. We used National Health and Nutrition Examination Surveys data to examine whether a higher self-perceived DQ was positively associated with a more optimal nutrient intake as reflected by the Food Nutrient Index (FNI) and Diet Quality Score (DQS). Comparative analyses were performed for three self-perceived DQ groups: (I) "excellent or very good" DQ, (II) "good or fair" DQ, and (III) "poor" DQ. The FNI and DQS differed substantially across groups and sexes. FNI scores ranged from 65 to 69 in participants with a self-reported excellent or very good DQ, whereas participants with a self-perceived poor DQ scored significantly lower (53-59). We also observed age- and sex-specific patterns, with the lowest overall FNI scores found in males aged 18-30 years and females aged 31-50 years. DQ intergroup differences were more pronounced in females than in males. Our findings suggest that higher self-perceived DQ is associated with a more optimal nutrient intake and indicate potential helpfulness of self-perceived DQ as a quick and still underexplored indicator with intrinsic limitations.

Ex vivo LPS-stimulated cytokine production is associated with hydration status in community-dwelling middle-to-older-aged adults

PURPOSE

Suboptimal hydration has been linked to a variety of adverse health outcomes. Few studies have examined the impact of hydration status on immune function, a plausible physiological mechanism underlying these associations. Therefore, we tested how variation in hydration status was associated with circulating pro-inflammatory cytokine levels and ex vivo lipopolysaccharide (LPS)-stimulated pro-inflammatory cytokine production.

METHODS

Blood samples were obtained from a community sample of healthy middle-to-older-aged adults (N = 72). These samples were used to assess serum osmolality, a biomarker of hydration status, and markers of immune function including circulating pro-inflammatory cytokines and stimulated pro-inflammatory cytokine production after 4 and 24 h of incubation with LPS. Multiple linear regressions were used to test the association between serum osmolality (as a continuous variable) and markers of immune function at baseline and after 4 and 24 h adjusting for age, sex, and BMI. These models were re-estimated with serum osmolality dichotomized at the cut-off for dehydration (> 300 mOsm/kg).

RESULTS

While not significantly associated with circulating cytokines (B = - 0.03, p = 0.09), serum osmolality was negatively associated with both 4 h (B = - 0.05, p = 0.048) and 24 h (B = - 0.05, p = 0.03) stimulated cytokine production when controlling for age, sex, and BMI. Similarly, dehydration was associated with significantly lower cytokine production at both 4 h (B = - 0.54, p = 0.02) and 24 h (B = - 0.51, p = 0.02) compared to adequate hydration.

CONCLUSION

These findings suggest that dehydration may be associated with suppressed immune function in generally healthy middle-to-older aged community-dwelling adults. Further longitudinal research is needed to more clearly define the role of hydration in immune function.

Carbohydrate Intake and Its Association With Dietary Acid Load in U.S. Adults: Results From a Cross-Sectional Study

Background: The safety profile of low-carbohydrate diets is controversial and poorly understood. We investigated the effects of low-moderate carbohydrate intake on dietary acid load (DAL), an emerging health risk factor and novel clinical marker associated with numerous adverse clinical outcomes. Methods: We used data from the National Health and Nutrition Examination Surveys to investigate how low-moderate carbohydrate intake quantitatively affects DAL (as assessed by PRAL and NEAP scores) and to contrast the results to DAL scores in individuals that meet carbohydrate intake recommendations. Results: We analyzed data from 23 825 individuals, of which 4891 consumed a low-moderate carbohydrate diet. Said individuals derived 37.84% of energy from carbohydrates, tended to be male, had a mean BMI of 28.47 kg/m2, and consumed significantly more energy from fat and protein ( P≤.01 for both) than individuals that met carbohydrate recommendations Low-moderate carbohydrate intake was associated with a significantly higher DAL. Mean PRALR, NEAPR, and NEAPF values were 26.12, 71.02, and 68.98 mEq/d, respectively. Multivariate regression revealed the highest DAL scores in individuals on a low-carbohydrate diet, obtaining <26% of energy from carbohydrates. Conclusions: Low-moderate carbohydrate intake is associated with increased DAL scores, which has been repeatedly associated with various health repercussions.

Children's water intake and hydration: a public health issue

Optimal hydration is required for all physiologic functions and cognition. Children, especially younger ones, are particularly susceptible to dehydration, given their physiological specificities, in particular, their renal immaturity and relatively large skin surface in early life, but also their dependence on adults and their greater propensity to develop digestive diseases leading to fluid losses. Mild dehydration consequences are dominated by their impact on cognitive functions, whereas more severe dehydration may endanger the health outcome. Studies on this subject in children are scarce; in particular, the long-term consequence on renal function remains questionable. This review considers how children's water intake including fluid intake and water content of food, are worrying. The findings show that, worldwide, most children do not meet adequate water intake recommendations. The main problems likely to explain insufficient water intake are access to safe water, availability of drinking water at school, and healthy-hydration education, which are all points that need to be improved within health policy.

Dietary Acid Load in Gluten-Free Diets: Results from a Cross-Sectional Study

The gluten-free diet (GFD) ensures improvement of clinical symptoms in the vast majority of celiac disease (CD) patients. Despite stable CD rates in many countries, an increasing number of healthy individuals are adopting gluten-free diets, believing that this diet is an inherently healthier choice. The health effects of gluten-free diets are controversial, and a recent study added to the debate by reporting a lower acidogenic potential of this diet. The effects of the GFD on potential renal acid load (PRAL) and net endogenous acid production (NEAP)—two important markers of dietary acid load (DAL)—are poorly understood, and have never been examined in a Western population. Using cross-sectional data from the National Health and Nutrition Examination Surveys, we estimated DAL in U.S. individuals reporting a GFD and contrasted the results to the general U.S. population consuming gluten and denying special diets. The GFD was associated with significantly lower crude DAL scores, and after adjustments for confounders in multivariate regression, the results remain significant. Yet, our study could not confirm the reported alkalizing properties of the GFD. Although overall DAL scores were significantly lower in the GFD group, they were comparable to Western diets producing 50–75 mEq of acid per day.

Reduced dietary acid load in U.S. vegetarian adults: Results from the National Health and Nutrition Examination Survey

Dietary acid load (DAL) is an important determinant of systemic pH and acid–base homeostasis. Diets abundant in acidogenic foods, such as meat and meat products, induce a low‐grade metabolic acidosis state that has been associated with cardiovascular disease, type‐2‐diabetes, and an increased cancer risk. Fruits and vegetables have alkalizing properties and beneficially affect DAL. It has thus been suggested that a plant‐based diet (restricting or excluding animal products) may be a powerful tool in reducing DAL; yet studies in that particular field are scarce. To explore these associations in greater detail, we examined DAL in self‐identified vegetarians from the United States National Health and Nutrition Examination Survey (2007–2010). We compared dietary intake and two widely used markers of DAL (PRAL (potential renal acid load) and NEAP (net endogenous acid production; NEAP_F and NEAP_R)) among 8,398 nonvegetarians and 191 lacto‐ovo‐vegetarians with reliable dietary intake aged 18 years or older. Vegetarians had a more favorable body mass index and consumed fewer calories (1862.31 kcal/d) than nonvegetarians (2041.12 kcal/d). Vegetarians consumed fewer protein (34.17 g/1000 kcal) and phosphorus compared to nonvegetarians (39.50 g of protein/1000 kcal) but had a higher intake of magnesium and potassium. Nonvegetarians exhibited higher median DAL scores (PRAL: 11.90 mEq/d, NEAP_F: 53.59 mEq/d, NEAP_R: 55.67 mEq/d) than vegetarians (PRAL: −0.44 mEq/d, NEAP_F: 39.60 mEq/d, NEAP_R: 41.30 mEq/d). Vegetarians had more favorable DAL scores compared to nonvegetarians in this descriptive epidemiologic study. Future (interventional) trials are warranted to examine the varying acid load in different plant‐based dietary patterns.

Current Hydration Habits: The Disregarded Factor for the Development of Renal and Cardiometabolic Diseases

Improper hydration habits are commonly disregarded as a risk factor for the development of chronic diseases. Consuming an intake of water below recommendations (underhydration) in addition to the substitution of sugar-sweetened beverages (SSB) for water are habits deeply ingrained in several countries. This behavior is due to voluntary and involuntary dehydration; and because young children are exposed to SSB, the preference for a sweet taste is profoundly implanted in the brain. Underhydration and SSB intake lead to mild hyperosmolarity, which stimulates biologic processes, such as the stimulation of vasopressin and the polyol-fructose pathway, which restore osmolarity to normal but at the expense of the continued activation of these biological systems. Unfortunately, chronic activation of the vasopressin and polyol-fructose pathways has been shown to mediate many diseases, such as obesity, diabetes, metabolic syndrome, chronic kidney disease, and cardiovascular disease. It is therefore urgent that we encourage educational and promotional campaigns that promote the evaluation of personal hydration status, a greater intake of potable water, and a reduction or complete halting of the drinking of SSB.

The Effect of EMG Features on the Classification of Swallowing Events and the Estimation of Fluid Intake Volume

Nowadays, society is experiencing an increase in the number of adults aged 65 and over, and it is projected that the older adult population will triple in the coming decades. As older adults are prone to becoming dehydrated, which can significantly impact healthcare costs and staff, it is necessary to advance healthcare technologies to cater to such needs. However, there has not been an extensive research effort to implement a device that can autonomously track fluid intake. In particular, the ability of surface electromyographic sensors (sEMG) to monitor fluid intake has not been investigated in depth. Our previous study demonstrated a reasonable classification and estimation ability of sEMG using four features. This study aimed to examine if classification and estimation could be potentiated by combining an optimal subset of features from a library of forty-six time and frequency-domain features extracted from the data recorded using eleven subjects. Results demonstrated a classification accuracy of 95.94 ± 2.76% and an f-score of 94.93 ± 3.51% in differentiating between liquid swallows from non-liquid swallowing events using five features only, and a volume estimation RMSE of 2.80 ± 1.22 mL per sip and an average estimation error of 15.43 ± 8.64% using two features only. These results are encouraging and prove that sEMG could be a potential candidate for monitoring fluid 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.

Association between Sensitivity to Thyroid Hormone Indices and Bone Mineral Density in US Males

OBJECTIVES

Thyroid hormone is acknowledged as a pivotal factor in skeletal development and adult bone maintenance. However, available data about the relationship between sensitivity to thyroid hormone and bone mineral density (BMD) remain limited and conflicting. The purpose of the study was to explore the complex relationship between sensitivity to thyroid hormone indices and BMD using cross-sectional analysis.

METHODS

An overall sample of 3,107 males from the National Health and Nutrition Examination Survey (NHANES) was studied in the study. The thyroid hormone sensitivity indices included free triiodothyronine/tree thyroxine (FT3/FT4), thyroid-stimulating hormone index (TSHI), thyrotroph thyroxine resistance index (TT4RI), and thyroid feedback quantile-based index (TFQI). Given the complex study design and sample weights, the correlation between sensitivity to thyroid hormone indices and BMD was evaluated through multivariate linear regression models, and extra subgroup analyses were performed to examine the robustness of the results.

RESULTS

Among the 3,107 participants, we demonstrated that FT3/FT4 was negatively correlated with lumbar BMD (β = -0.0.35, 95% CI: -0.084-0.013, P < 0.05). In the terms of central sensitivity to thyroid hormone, TFQI showed a significant negative relationship with the BMD of the lumbar (β = -0.018, 95% CI: -0.033 to -0.003, P < 0.05), total femur (β = -0.020, 95% CI: -0.035 to -0.006, P < 0.01), and femur neck (β = -0.018, 95% CI: -0.031 to -0.005, P < 0.01). In the subgroup analyses stratified by body mass index (BMI), the significant negative correlation between TFQI and lumbar BMD remained in the male participants with BMI between 18.5 and 24.9 kg/m².

CONCLUSIONS

Decreased indices of sensitivity to thyroid hormones are strongly associated with increased lumbar BMD, suggesting that the dysfunction of peripheral and central response to thyroid hormone might contribute to bone loss. In addition, FT3/FT4 and TFQI were considered to be the preferable indicators to guide the prevention and clinical treatment of osteoporosis.

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.

The association of urine osmolality with decreased kidney function and/or albuminuria in the United States

Background

Decreased kidney function is commonly caused by hypovolemia. When hypovolemic, the kidney reabsorbs water resulting in concentrated urine. Osmolality is a measure of urine concentration which is more objective than self-reported fluid intake. It has a positive association with hypovolemia. However, it remains controversial whether osmolality is associated with decreased kidney function and/or albuminuria.

Methods

We conducted a cross-sectional analysis of the 2009–2012 National Health and Nutrition Examination Survey, a standardized survey in the U.S. population. Participants aged 18–70 years old with random urine osmolality were included. Osmolality was categorized as quartiles. Decreased kidney function was defined by estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m² and albuminuria was defined by albumin-to-creatinine ratio ≥ 30 mg/gm. We performed multivariable regression via four sequential models.

Results

Our study sample included 7,373 participants. The mean age was 42.9 ± 0.4 years. Overall, 51.4% were male and 67.3% were white. The mean osmolality was 603.8 mOsm/kg and 629.1 mOsm/kg in those with and without decreased eGFR and/or albuminuria, respectively. The number of cases was 610 (6.7%). The prevalence from the lowest to highest quartiles of osmolality was 116 (6.2%), 213 (8.6%), 179 (7.5%), and 102 (4.3%), respectively (p-value for trend = 0.02). The relationship between osmolality and eGFR appeared nonlinear. After adjustment for demographic, social, cardiovascular, and dietary risk factors, there was no significant association of osmolality quartiles with decreased eGFR and/or albuminuria (odds ratio [OR] 0.77, 95% confidence interval [CI] 0.56, 1.07). In sensitivity analyses, osmolality ≥ 500 mOsm/kg was associated with lower eGFR (adjusted ß -1.13, 95% CI -1.98, -0.28). In pre-specified subgroup analyses, osmolality had a statistically significant negative correlation with eGFR among individuals with eGFR ≥ 60 mL/min/1.73m², but a positive correlation among those with eGFR < 60 mL/min/1.73m² (adjusted ß -0.19, 95% CI -0.36, -0.01 versus adjusted ß 0.50, 95% CI 0.05, 0.96; p-value for interaction = 0.016).

Conclusions

Higher osmolality was significantly associated with lower eGFR among adults with eGFR ≥ 60 mL/min/1.73m² Future research should examine the relationship between osmolality and change in kidney function over time among adults with normal eGFR.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02478-9.

Hydration status, body composition, and anxiety status in aeronautical military personnel from Spain: a cross-sectional study

BACKGROUND

An adequate hydration status is critical to ensure efficiency during mental and physical activities. Our goal was to assess the hydration status of a Spanish group of aeronautical military men and to determine the association of hydration status with body composition and anxiety.

METHODS

A total of 188 men were evaluated through a validated hydration questionnaire, anthropometric and biochemical parameters, and an anxiety questionnaire. Based on these methods, the criteria of hydration were established.

RESULTS

Of the total sample, 81% met the hydration criteria (urine color = well hydrated, water balance ≥ 0 ml, and total water intake/weight ≥ 35 ml/kg), and 19% did not meet the hydration criteria (urine color = not sufficiently hydrated or dehydrated, water balance < 0 ml, and total water intake/weight < 35 ml/kg). Subjects not meeting the hydration criteria had lower urine pH, negative water balance, and lower water intake. The latter also had higher anxiety status (score = 4 vs. 3, P = 0.026), weight [(84.7 ± 10.5) vs. (80.5 ± 10.2) kg], body mass index [(26.3 ± 3.1) vs. (25.2 ± 2.8)]kg/m², body fat [(22.3 ± 5.6) vs. (18.3 ± 6.5)] %, urine specific gravity, and urine color. Using a logistic binary regression model, hydration status was related significantly with the percentage of body fat (P = 0.004), but no relation was found with age, comorbidities, or medications. Furthermore, total water intake/weight was positively correlated with percentage of body water (r = 0.357, P = 0.000) and negatively with body fat (kg) (r = - 0.427, P = 0.000), percentage of body fat (r = - 0.405, P = 0.000), and waist/hip ratio (r = - 0.223, P = 0.002). Based on a linear regression model, total water intake/weight was related significantly with percentage of body fat (P = 0.001) and percentage of body water content (P = 0.035). No relation was found, however, with waist/hip ratio, age, comorbidities, or medications.

CONCLUSIONS

These findings all suggest a relationship between hydration status and body composition but also set the bases for future studies that relate hydration status and anxiety status. These results can be used to improve the hydration status and body composition of military personnel.

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.

Water Researchers Do Not Have a Strategic Plan for Gathering Evidence to Inform Water Intake Recommendations to Prevent Chronic Disease

Confusion has persisted for decades in the United States (U.S.) over how much plain water to drink, despite national water intake recommendations which are based on high quality scientific evidence. This editorial summarizes the definition, alignment and coordination of evidence that informs the current U.S. adequate intake (AI) recommendations for water. It highlights gaps in the evidence that perpetuate confusion and opportunity to address the gaps through strategic planning.

Drinking Water in the United States: Implications of Water Safety, Access, and Consumption

Recent water quality crises in the United States, and recognition of the health importance of drinking water in lieu of sugar-sweetened beverages, have raised interest in water safety, access, and consumption. This review uses a socioecological lens to examine these topics across the life course. We review water intakes in the United States relative to requirements, including variation by age and race/ethnicity. We describe US regulations that seek to ensure that drinking water is safe to consume for most Americans and discuss strategies to reduce drinking water exposure to lead, a high-profile regulated drinking water contaminant. We discuss programs, policies, and environmental interventions that foster effective drinking water access, a concept that encompasses key elements needed to improve water intake. We conclude with recommendations for research, policies, regulations, and practices needed to ensure optimal water intake by all in the United States and elsewhere.

Underhydration Is Associated with Obesity, Chronic Diseases, and Death Within 3 to 6 Years in the U.S. Population Aged 51-70 Years

Nationally representative data from the National Health and Nutrition Examination Survey (NHANES) indicate that over 65% of adults aged 51–70 years in the U.S. do not meet hydration criteria. They have hyponatremia (serum sodium < 135 mmol/L) and/or underhydration (serum sodium >145 mmol/L, spot urine volume <50 mL, and/or spot urine osmolality ≥500 mmol/kg). To explore potential public health implications of not meeting hydration criteria, data from the NHANES 2009–2012 and National Center for Health Statistics Linked Mortality Files for fasting adults aged 51–70 years (sample n = 1200) were used to determine if hyponatremia and/or underhydration were cross-sectionally associated with chronic health conditions and/or longitudinally associated with chronic disease mortality. Underhydration accounted for 97% of the population group not meeting hydration criteria. In weighted multivariable adjusted Poisson models, underhydration was significantly associated with increased prevalence of obesity, high waist circumference, insulin resistance, diabetes, low HDL, hypertension, and metabolic syndrome. Over 3–6 years of follow-up, 33 chronic disease deaths occurred in the sample, representing an estimated 1,084,144 deaths in the U.S. Alongside chronic health conditions, underhydration was a risk factor for an estimated 863,305 deaths. Independent of the chronic health conditions evaluated, underhydration was a risk factor for 128,107 deaths. In weighted multivariable Cox models, underhydration was associated with 4.21 times greater chronic disease mortality (95% CI: 1.29–13.78, p = 0.019). Zero chronic disease deaths were observed for people who met the hydration criteria and did not already have a chronic condition in 2009–2012. Further work should consider effects of underhydration on population health.

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.

Hydration Status and Cardiovascular Function

Hypohydration, defined as a state of low body water, increases thirst sensations, arginine vasopressin release, and elicits renin–angiotensin–aldosterone system activation to replenish intra- and extra-cellular fluid stores. Hypohydration impairs mental and physical performance, but new evidence suggests hypohydration may also have deleterious effects on cardiovascular health. This is alarming because cardiovascular disease is the leading cause of death in the United States. Observational studies have linked habitual low water intake with increased future risk for adverse cardiovascular events. While it is currently unclear how chronic reductions in water intake may predispose individuals to greater future risk for adverse cardiovascular events, there is evidence that acute hypohydration impairs vascular function and blood pressure (BP) regulation. Specifically, acute hypohydration may reduce endothelial function, increase sympathetic nervous system activity, and worsen orthostatic tolerance. Therefore, the purpose of this review is to present the currently available evidence linking acute hypohydration with altered vascular function and BP regulation.