The role of obesity in the relation between total water intake and urine osmolality in US adults, 2009-2012

Is There an Association Between Hydration Status, Beverage Consumption Frequency, Blood Pressure, Anthropometric Characteristics, and Urinary Biomarkers in Adults?

OBJECTIVES

Hydration is essential for overall health; therefore, this study aimed to identify associations between hydration status and beverage consumption, anthropometric measures, and urine biochemical analyses in Polish adults. Poland was chosen due to potential regional dietary habits and hydration patterns that may influence hydration status.

METHODS

A total of 337 participants completed a beverage frequency questionnaire (FFQ). Blood pressure (BP), anthropometric parameters, and body composition were measured. Urine samples were analyzed for specific gravity (USG), osmolality (Uosm), and potential hydrogen value (pH). Hydration status was assessed using the WUT model (weight, urine color, thirst level), classifying participants into two groups: dehydrated (2-3 WUT components) and properly hydrated (0-1 WUT component). Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

RESULTS

Approximately 50% of participants (n = 165) exhibited dehydration symptoms, including higher thirst levels, darker urine, and elevated USG and Uosm (p ≤ 0.05). Dehydrated individuals more frequently reported fatigue (p = 0.009), headaches (p = 0.024), and heavy legs (p = 0.002). Higher BMI (OR: 1.49), waist circumference (OR: 1.79), USG (OR: 2.29), and Uosm (OR: 1.75) increased dehydration risk. Conversely, greater consumption of tea (OR: 0.52) and non-carbonated mineral water (OR: 0.45), higher total body water (OR: 0.49), and handgrip strength (OR: 0.81) were linked to lower dehydration risk. Four dietary patterns were identified: Reasonable, Unhealthy, Minimalist, and Loving Sweet Beverages.

CONCLUSIONS

Multifactorial hydration assessment, combined with preventive strategies such as regular fluid intake and weight management, may improve hydration. The WUT model and Venn diagram provide a practical tool for hydration assessment in clinical and public health.

Associations between urine specific gravity and race/ethnicity at the population level: Implications for hydration status categorization

OBJECTIVE

We aimed to evaluate how urine specific gravity (USG) and rates of supposed hypohydration vary by race/ethnicity, and to examine how adjustment for several important factors impacts estimated USG.

METHODS

Using the National Health and Nutrition Examination Survey, this cross-sectional study evaluated a total of 4195 (2098 female, 2097 male) Americans and categorized them as supposedly hypohydrated (USG≥1.020) or not using spot urine samples. USG and prevalence of supposed hypohydration were compared across racial/ethnic groups, separately by gender. The analyses considered the impact of urine creatinine, body composition, age, dietary nutrients, and physical activity.

RESULTS

Differences in supposed hypohydration prevalence were observed by race/ethnicity in men (p = .030) and women (p < .001). In unadjusted models, Black women's USG (1.0189) was higher (p < .05) than all the other race/ethnicity groups' USG (1.0142-1.0171). In men, Blacks' USG (1.0197) was higher (p < .05) than the USG of Whites (1.0177) and other/multi-racial (1.0176) but not Mexican Americans (1.0196) or other Hispanics (1.0192). Adjustments for age, arm circumference, nutrients (protein, sodium, potassium, and moisture), and physical activity minimally influenced USG estimates. Further adjustment for urine creatinine lowered USG for Black women and men by 0.003 and 0.0023, respectively, with no notable lowering of USG in the other races/ethnicities. Supplemental analyses matching Whites and Blacks on age, moisture intake, and poverty-to-income ratio confirmed racial differences in urine creatinine and USG, though the effects were most pronounced in women.

CONCLUSIONS

Using a USG≥1.020 to identify hypohydration in all races/ethnicities may be inappropriate due to, among other factors, differences in urinary creatinine.

Hydration status in adults with metabolic disorders in relation to socioeconomic, lifestyle and health factors

INTRODUCTION

Adequate hydration is essential for maintaining the health and functionality of the human body. This study aimed to examine the association between selected socioeconomic, lifestyle, and health factors and the hydration status of adults with metabolic disorders by analyzing their urine osmolality.

METHODS

The study involved 290 adults aged 18-70 years with metabolic disorders. Separate multivariate logistic regression models were conducted to evaluate the factors associated with urine osmolality in tertiles for women and men. Odds Ratios (OR) and 95% Confidence Intervals (95% CI) were calculated.

RESULTS

In women, the following factors of urine osmolality were identified in 1st tertile: age (OR:1.04), physical activity (moderate/high vs. no/low; OR:0.38), and headaches (no vs. yes; OR:1.55), in 2nd tertile: physical activity (moderate/high vs. no/low; OR:2.46) and fatigue during the day (sometimes vs. never/very rarely; OR:0.45), and in 3rd tertile: age (OR:0.94), professional status ('I work part-time/I study and I work' vs. 'I do not work/I study'; OR:0.27), fatigue during the day (very often vs. never/very rarely; OR:2.55), and headaches (no vs. yes; OR:0.44). In men, the following factors of urine osmolality were identified in 1st tertile: place of residence (city vs. village; OR:2.72) and health assessment (average vs. poor; OR:0.32).

CONCLUSION

Different factors affecting urine osmolality have been identified in women and men. These results highlight the need to implement studies to clarify the relationship between socioeconomic, lifestyle and health factors, and hydration status in adults with metabolic disorders.

Plasma Uric Acid, Lactate, and Osmolality in Colorectal Cancer

A complex evaluation of colorectal cancer (CRC) in relation to screening, diagnosis, stage determination, prognosis, and treatment requires valuable biomarkers. The aim of this study was to measure selected biomarkers—uric acid (UA), lactate, Na+, Cl−, and osmolality—in CRC patients and to assess their diagnostic value to distinguish between CRC and healthy controls. Plasma lactate (2.21 ± 0.11 vs. 2.88 ± 0.19, p < 0.01), Na+ (130.79 ± 0.42 vs. 133.23 ± 0.25, p < 0.001), Cl− (102.59 ± 0.45 vs. 103.94 ± 0.23, p < 0.01), and osmolality (266.44 ± 0.86 vs. 271.72 ± 0.62, p < 0.001) were found to be significantly lower in CRC patients as compared to the healthy controls group. Among them, with satisfactory diagnostic potential, were plasma Na+ concentrations and osmolality (AUCNa+ = 0.752, p < 0.0001; AUCosmolality = 0.757, p < 0.05), respectively. UA concentrations were detected at higher concentrations in CRC patients (333.67 ± 13.05 vs. 295.88 ± 13.78, p < 0.05). The results of this study contribute to the elucidation of molecular mechanisms of CRC pathogenesis and the role of studied metabolic parameters in this process. Plasma uric acid, lactate, and osmolality parameters can be used for screening and monitoring colorectal cancer. Further studies are required to elucidate the molecular mechanisms of their action in cancer development. The action of circulating plasma lactate may be different from those locally produced in the tumor microenvironment.

Ad libitum dehydration is associated with poorer performance on a sustained attention task but not other measures of cognitive performance among middle-to-older aged community-dwelling adults: A short-term longitudinal study

OBJECTIVE

Hydration status and water intake are critical to physiological health. Despite a popular narrative that dehydration impairs cognitive performance, results are mixed in the literature. Therefore, we tested how hydration status was associated with cognitive performance in an ad libitum state over the course of 3 months.

METHODS

Data come from a short-term longitudinal study among middle-to-older aged US adults (n = 78) measured three times (207 observations). All participants were scheduled for 8:00 a.m. visits for the baseline, two-week, and 3-month examinations where they completed surveys, neuropsychological tests to measure cognitive performance, anthropometrics, and a blood draw for biomarker analysis. Serum osmolality (Sosm) was measured as a biomarker of hydration status using osmometry. Four cognitive performance tasks were assessed, including inhibition, working memory, cognitive flexibility, and sustained attention.

RESULTS

Panel random effects linear regressions demonstrate that there was an inverse association between dehydration and sustained attention, whereas there were no significant relationships between dehydration and inhibition, working memory, and cognitive flexibility. Adults who were dehydrated (defined as Sosm >300 mOsm/kg) performed substantially worse (B = 0.65 z-score; SE = 0.28; p = .020) on the sustained attention task than those who were not dehydrated adjusting for time fixed effects, age, body mass index, sex, and educational attainment.

CONCLUSION

This short-term longitudinal study found that dehydration was only associated with poorer performance on a cognitive performance task that required sustained attention. Maintaining adequate hydration may be increasingly important for middle-to-older aged adults to ensure proper cognitive function, particularly as water needs increase in future climatic scenarios.

Detection of low urine output by measuring urinary biomarkers

BACKGROUND

Urine output < 1 L per 24 h is a clinical warning sign that requires attention from hospital staff, who should determine whether the low flow is due to low habitual intake of water or disease-induced dehydration. The incidence of this condition is unclear.

METHODS

A cohort of 20 healthy volunteers (mean age 42 years, range 23-62 years) recorded their food and water intakes daily for 8 days. They also collected and measured all urine and delivered first morning urine samples for analysis of osmolality and creatinine. Optimal cutoffs for these biomarkers to indicate urine output of < 1 L or 15 mL/kg during the preceding 24 h were applied with and without correction for age to cross-sectional data from 1,316 subjects in various clinical settings, including healthy volunteers, preoperative patients, patients seeking acute care at a hospital, and patients receiving institutional geriatric care.

RESULTS

The urine output amounted to < 1 L during 22 of the 159 evaluable study days and was indicated by urine osmolality > 760 mosmol/kg or urine creatinine > 13 mmol/L, which had sensitivity and specificity of approximately 80%. Days with urine output < 1 L were associated with significantly less intake of both water (-41%) and calories (-22%) compared to other days. Application of age-corrected biomarker cutoffs to the 1,316 subjects showed a stronger dependency of low urine output on age than the clinical setting, occurring in 44% of the 72 participants aged 15-30 years and 18% of the 62 patients aged 90-104 years.

CONCLUSION

Biomarkers measured in morning urine of young and middle-aged volunteers indicated urine output of < 1 L with good precision, but the cutoffs should be validated in older age groups to yield reliable results.

TRIAL REGISTRATIONS

ISRCTN12215472 at http://www.isrctn.com ; NCT01458678 at ClinicalTrials.gov, and ChiCTR-TNRC-14,004,479 at the chictr.org/en.

Identifying the main predictors of urine output in autosomal-dominant polycystic kidney disease (ADPKD) patients taking tolvaptan

BACKGROUND

Few works have analyzed factors associated with urine output in ADPKD patients taking tolvaptan (TVP).

METHODS

We selected 24-h urine samples from ADPKD patients treated with TVP. Urine osmolality/creatinine ratio was used as estimator of urinary osmolar load.

RESULTS

We included 127 urine samples from 61 patients. After TVP, urine output doubled with a parallel reduction in urine solute concentration. However, when expressed as urine solute/creatinine ratios, no significant changes were observed. Daily osmolar load and osmolality/creatinine ratio did not change significantly. Before TVP, urine output was positively correlated with body weight and urine osmolality/creatinine ratio and negatively with eGFR, urine morning osmolality, and 24-h urine-calculated osmolality. After TVP, urine output was positively correlated with body weight, eGFR and negatively with age. There was a poor correlation with urine-calculated osmolality. We constructed a predictor model using mixed-effects modeling and we found that urine output was related to lower age, higher body weight, higher eGFR, and greater doses of TVP. When body weight was removed, urine output was also related to male sex and a higher daily osmolar excretion. Equation of prediction was: Urine output (mL/day) = 2771-52.9 × Age (years) + 58.4 × Weight (kg) + 18.7 × eGFR (mL/min) + 870 (if TVP = 90/30 mg) + 517 (if TVP = 60/30 mg).

CONCLUSION

Patients taking TVP will undergo an increase about twice in urine production from baseline. Greater doses of TVP cause a progressive increase in urine production. GFR, age, and body weight are the main predictors of future urine output in patients taking TVP.

Water intake, hydration status and 2-year changes in cognitive performance: a prospective cohort study

BACKGROUND

Water intake and hydration status have been suggested to impact cognition; however, longitudinal evidence is limited and often inconsistent. This study aimed to longitudinally assess the association between hydration status and water intake based on current recommendations, with changes in cognition in an older Spanish population at high cardiovascular disease risk.

METHODS

A prospective analysis was conducted of a cohort of 1957 adults (aged 55-75) with overweight/obesity (BMI between ≥ 27 and < 40 kg/m2) and metabolic syndrome from the PREDIMED-Plus study. Participants had completed bloodwork and validated, semiquantitative beverage and food frequency questionnaires at baseline, as well as an extensive neuropsychological battery of 8 validated tests at baseline and 2 years of follow-up. Hydration status was determined by serum osmolarity calculation and categorized as < 295 mmol/L (hydrated), 295-299.9 mmol/L (impending dehydration), and ≥ 300 mmol/L (dehydrated). Water intake was assessed as total drinking water intake and total water intake from food and beverages and according to EFSA recommendations. Global cognitive function was determined as a composite z-score summarizing individual participant results from all neuropsychological tests. Multivariable linear regression models were fitted to assess the associations between baseline hydration status and fluid intake, continuously and categorically, with 2-year changes in cognitive performance.

RESULTS

The mean baseline daily total water intake was 2871 ± 676 mL/day (2889 ± 677 mL/day in men; 2854 ± 674 mL/day in women), and 80.2% of participants met the ESFA reference values for an adequate intake. Serum osmolarity (mean 298 ± 24 mmol/L, range 263 to 347 mmol/L) indicated that 56% of participants were physiologically dehydrated. Lower physiological hydration status (i.e., greater serum osmolarity) was associated with a greater decline in global cognitive function z-score over a 2-year period (β: - 0.010; 95% CI - 0.017 to - 0.004, p-value = 0.002). No significant associations were observed between water intake from beverages and/or foods with 2-year changes in global cognitive function.

CONCLUSIONS

Reduced physiological hydration status was associated with greater reductions in global cognitive function over a 2-year period in older adults with metabolic syndrome and overweight or obesity. Future research assessing the impact of hydration on cognitive performance over a longer duration is needed.

TRIAL REGISTRATION

International Standard Randomized Controlled Trial Registry, ISRCTN89898870. Retrospectively registered on 24 July 2014.

MUSCLE DEPLETED OBESITY IN INDIVIDUALS SCREENED FOR COLORECTAL CÂNCER

BACKGROUND

Colorectal cancer (CRC) is the third most incident cancer in the world and the second leading cause of cancer death. Significant decreases in incidence and mortality can be achieved by reducing risk factors and adhering to healthy lifestyle recommendations, as well as screening for the disease.

OBJECTIVE

To evaluate the clinical nutritional profile of individuals at medium risk screened for CRC residing in the city of Piranhas/Alagoas.

METHODS

Cross-sectional study conducted from September to October 2020, with individuals at medium risk for CRC, of both sexes and aged between 50 and 70 years old. Participants were screened for CRC with fecal immunochemical testing (FIT) and colonoscopy. Personal, socioeconomic, clinical, lifestyle and nutritional assessment data were collected. The latter was performed using anthropometric data (weight, height, arm circumference and triceps skinfold thickness), body composition (bioimpedance) and physical examination. Descriptive analysis of data frequencies and dichotomization according to the presence or absence of overweight was performed, followed by comparison of means and medians and frequencies by chi-square or Fisher's exact test.

RESULTS

In total, 82 people agreed to undergo the clinical nutritional assessment, most of them female (56.1%; n=46), adults (56.1%; n=46), with a mean age of 59.02 years (±6.30 SD). Pre-cancerous lesions were identified in 54.5% (n=42) of those screened, 52.4% (n=43) were smokers or former smokers, and 65.9% (n=54) did not practice scheduled physical activity. Nutritional assessment showed that 64.6% (n=53) were overweight according to body mass index. On the other hand, the muscle mass, % arm muscle circumference adequacy and body muscle mass (kg) markers showed that 32.9% (n=27) and 47.6% (n=39) of the subjects were muscle depleted, respectively. Above all, overweight participants had, in parallel, lower muscle mass (P<0.05), suggesting sarcopenic obesity in this population.

CONCLUSION

Obesity is one of the main risk factors for CRC; when concomitant with sarcopenia, it favors worse health outcomes. In this context, evidence shows the need to assess muscle composition in people with obesity, especially through other methods of assessing body composition. Our results add to the evidence on the importance of the population being guided about screening and adherence to healthy lifestyle recommendations, especially strategies aimed at weight control and the practice of physical activity.

THIRSTY FOR FRUCTOSE: Arginine Vasopressin, Fructose, and the Pathogenesis of Metabolic and Renal Disease

We review the pathways by which arginine vasopressin (AVP) and hydration influence the sequelae of the metabolic syndrome induced by high fructose consumption. AVP and inadequate hydration have been shown to worsen the severity of two phenotypes associated with metabolic syndrome induced by high fructose intake-enhanced lipogenesis and insulin resistance. These findings have implications for those who frequently consume sweeteners such as high fructose corn syrup (HFCS). Patients with metabolic syndrome are at higher risk for microalbuminuria and/or chronic kidney disease; however, it is difficult to discriminate the detrimental renal effects of the metabolic syndrome from those of hypertension, impaired glucose metabolism, and obesity. It is not surprising the prevalence of chronic renal insufficiency is growing hand in hand with obesity, insulin resistance, and metabolic syndrome in those who consume large amounts of fructose. Higher AVP levels and low hydration status worsen the renal insufficiency found in patients with metabolic syndrome. This inter-relationship has public health consequences, especially among underserved populations who perform physical labor in environments that place them at risk for dehydration. MesoAmerican endemic nephropathy is a type of chronic kidney disease highly prevalent in hot ambient climates from southwest Mexico through Latin America. There is growing evidence that this public health crisis is being spurred by greater fructose consumption in the face of dehydration and increased dehydration-dependent vasopressin secretion. Work is needed at unraveling the mechanism(s) by which fructose consumption and increased AVP levels can worsen the renal disease associated with components of the metabolic syndrome.

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.

Effects of Jowiseungki-tang on high fat diet-induced obesity in mice and functional analysis on network pharmacology and metabolomics analysis

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Chinese and Korean medicine, Jowiseungki-tang (JST) is a prescription for diabetes mellitus (DM) treatment. However, little scientific evidence is known of its effect in diabetic condition.

AIMS

We assessed the effects of JST on high-fat diet (HFD)-induced obesity with inflammatory condition in mice and to analyze the therapeutic function of JST on network pharmacology as well as targeted metabolomics.

MATERIALS AND METHODS

JST administration at 100 mg/kg and 500 mg/kg for a period of 4 weeks in HFD-induced obese mice, body weight gain, energy utility, calorie intake, and levels of glucose, insulin, total cholesterol, triglyceride, LDL-cholesterol as well as interleukin-6 were measured. Measurements of HDL-cholesterol (HDL-C) were performed and compared to those of the control group. Moreover, the therapeutic function of JST on obesity was analyzed furtherly based on network pharmacology and targeted metabolomics methods.

RESULTS

Administration of JST at 100 mg/kg and 500 mg/kg for a period of 4 weeks in HFD-induced obesity mice significantly decreased the body weight gain, energy utility, calorie intake, and levels of insulin, total cholesterol, LDL-cholesterol, triglyceride, and interleukin-6. However, HDL-cholesterol (HDL-C) levels showed marked elevation relative to control groups. JST administration strongly inhibited expressions of inducible nitric oxide synthase, inflammatory proteins, and cyclooxygenase-2 in the pancreas, stomach, and liver tissues, and reduced hepatic steatosis and pancreatic hyperplasia. In network pharmacological analysis, the putative functional targets of JST are underlie on modulation of cofactor-, coenzyme-, and fatty acid-bonding, insulin resistance, and inflammatory response, fine-tuned the phosphatase binding and signal pathway activation, such as mitogen activated protein kinases, phosphatidylinositol 3-kinases/protein kinase B, protein kinase C, and receptor of glycation end products as well-advanced glycation end products. According to the metabolomics analysis, the contents and energy metabolites, and medium and long chain fatty acids was significantly changed in mice pancreases.

CONCLUSIONS

JST is a valuable prescription for treatment of patients with DM in traditional clinics through inhibition of obesity, inflammatory condition and metabolism.

Comparing thirst and spot urine concentrations in humans of differing body sizes: An observational study

Elevated body mass index (BMI) has been associated with elevated urine osmolality (UOsm), despite having higher total water intake, but it is unclear if overweight/obese individuals have reduced thirst. In this observational study, we found that overweight/obese individuals had higher UOsm compared to normal-weight individuals (749 ± 37 vs. 624 ± 35 mmol•kg^-1; P < 0.01) while possessing similar thirst ratings (56.4 ± 3 vs. 51.6 ± 3 mm; P = 0.3). In this observational study, overweight/obese individuals possessed more concentrated urine in the absence of higher thirst perception.

Water Intake and Markers of Hydration Are Related to Cardiometabolic Risk Biomarkers in Community-Dwelling Older Adults: A Cross-Sectional Analysis

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.

Associations of Urine Specific Gravity With Body Mass Index and Lean Body Mass at the Population Level: Implications for Hydration Monitoring

Urine specific gravity (USG) thresholds are used in practice and research to determine hypohydration. However, some limited research has found that body size and body composition may impact USG, suggesting that fixed cutoffs may be insensitive. Cross-sectional data from 3,634 participants of the 2007-2008 National Health and Nutrition Examination Survey were analyzed. Along with USG, body mass index (BMI), estimated lean body mass (LBM), and dietary intake were quantified. Logistic regression models were used to evaluate whether higher quintiles of BMI and LBM were associated with elevated USG (USG ≥ 1.020 and ≥1.025) after accounting for dietary moisture and sodium. The USG (1.018 ± 0.0003 vs. 1.015 ± 0.0004); BMI (28.4 ± 0.2 vs. 28.0 ± 0.2 kg/m2); LBM (60.9 ± 0.3 vs. 42.2 ± 0.2 kg); dietary moisture (3,401 ± 92 vs. 2,759 ± 49 g/day); and dietary sodium (4,171 ± 85 vs. 2,959 ± 50) were greater in men than in women (p < .05). Men and women in the fifth quintiles of BMI or LBM (vs. Quintile 1) had greater odds (2.00-3.68, p < .05) of elevated USG. (The only exception was for the association between BMI and USG ≥ 1.025 in men.) Being in Quintile 4 of LBM or BMI (vs. Quintile 1) also tended to be associated with higher odds of elevated of USG, though this pattern was more consistent when using USG ≥ 1.020 than USG ≥ 1.025. In summary, BMI and LBM are associated with USG at the population level. These results affirm that USG depends on body size and composition and raise questions about using fixed USG thresholds for determining hypohydration, particularly for people in the upper quintiles of BMI and LBM.

Evaluation of hydration status during the COVID-19 pandemic: a study of Turkish young adults

Adequate hydration is an essential component of health at every stage of life. Although many factors such as age, gender, physical activity, drug use, and illness affect hydration status, it is vital to maintain water balance, especially in infectious diseases. This study was conducted to estimate the hydration status of young adults living in Turkey during the COVID-19 pandemic. The total water intake (TWI) and total water loss of the individuals were determined using the Water Balance Questionnaire (WBQ), which consists of questions about physical activity status, frequency of food and beverage consumption, water consumption, and water loss with urine and feces. The TWI of men and women was found to be 4,776.1 and 4,777.3 mL/day, respectively (p > 0.05). It was determined that 29% of the total water was obtained from drinking water, 49% from other beverages, and 22% from food. A positive net water balance was found in all body mass index (BMI) groups, men, and women. The net water balance was statistically lower in men (2,230.6 mL) than women (2,783.8 mL) (p < 0.05). As the COVID-19 pandemic continues, studies should be done on hydration status in the more balanced populations in terms of BMI and age groups.

The importance of the compartment model of body composition analysis in women with severe obesity

Introduction: Usually, the diagnosis of obesity is only based on body mass index (BMI), which may lead to a non-reliable body composition analysis. Objective: To analyze the body characteristics of morbidly obese (class III) women referred to bariatric surgery using the compartment model of body composition analysis. Materials and methods: Cross-sectional study conducted in 2017 in 14 morbidly obese women aged between 25 and 51 years who were undergoing clinical and physical therapy assessment prior to undergoing bariatric surgery at a university hospital in Rio de Janeiro, Brazil. Body composition analysis was performed using an octopolar bioimpedance scale. The Pearson's correlation coefficient was used to analyze the correlation between variables, with a significance level of p<0.5. Results: A high mean percentage of fat body was observed (51.2%), mainly in the trunk. BMI was correlated with total fat in kilograms (r=0.63), and muscle mass (r=0.60); besides, a moderate correlation with the waist-to-hip ratio (WHR) was found (r=0.55). WHR showed a correlation with TBF% (r=0.60) and a moderate correlation with total fat in kilograms (r=0.57). In addition, the sarcopenia index was correlated with muscle mass (r=0.79) and total body water (r=0.78). All these correlations were statistically significant (p<0.05). There were no sarcopenia cases. Conclusion: A higher concentration of fat in the trunk and the upper limbs was observed in the study population, however none of the participants had sarcopenia. On the other hand, BMI showed a greater correlation with both total fat (kg) and TBF% than with WHR. Such findings suggest that assessing these patients based only on BMI or WHR may hinder the development individualized treatment strategies.

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.

Physiological factors characterizing heat-vulnerable older adults: A narrative review

More frequent and intense periods of extreme heat (heatwaves) represent the most direct challenge to human health posed by climate change. Older adults are particularly vulnerable, especially those with common age-associated chronic health conditions (e.g., cardiovascular disease, hypertension, obesity, type 2 diabetes, chronic kidney disease). In parallel, the global population is aging and age-associated disease rates are on the rise. Impairments in the physiological responses tasked with maintaining homeostasis during heat exposure have long been thought to contribute to increased risk of health disorders in older adults during heatwaves. As such, a comprehensive overview of the provisional links between age-related physiological dysfunction and elevated risk of heat-related injury in older adults would be of great value to healthcare officials and policy makers concerned with protecting heat-vulnerable sectors of the population from the adverse health impacts of heatwaves. In this narrative review, we therefore summarize our current understanding of the physiological mechanisms by which aging impairs the regulation of body temperature, hemodynamic stability and hydration status. We then examine how these impairments may contribute to acute pathophysiological events common during heatwaves (e.g., heatstroke, major adverse cardiovascular events, acute kidney injury) and discuss how age-associated chronic health conditions may exacerbate those impairments. Finally, we briefly consider the importance of physiological research in the development of climate-health programs aimed at protecting heat-vulnerable individuals.

Total body water by BIA in children and young adults with normal and excessive weight

Background

Estimation of total body water (TBW) is essential for clinical care.

Objective

Evaluation of changes in TBW by bioelectrical impedance analysis (BIA) in children and young adults with excessive weight.

Design

Data was collected in individuals aged 3–21 years with normal (n = 202) or excessive body weight (n = 133). The BIA results from individuals with normal weight were compared with two previously published studies in children by isotope dilution methods.

Results

Individuals with excessive weight had a higher mean TBW (27.87 L, SE 0.368) for height and age as compared to individuals with normal weight (23.95 L, SE 0.298), P<0.001. However, individuals with excessive weight had lower mean TBW (24.93 L, SE 0.37) for weight and body surface area (BSA) as compared to individuals with normal weight (26.94 L, SE 0.287), P<0.001. Comparison with two previously published studies showed no significant differences in mean TBW with one ((p = 1.00) but a significant difference with another study (p = 0.001).

Conclusions

Individuals with excessive weight had 16.5% higher mean TBW for height and age and 7.4% lower TBW for weight and BSA as compared to normal weight individuals. Our study validates the feasibility of data collection in pediatric outpatient setting by BIA.

Hydration in relation to water insecurity, heat index, and lactation status in two small-scale populations in hot-humid and hot-arid environments

OBJECTIVES

This study compared the prevalence of concentrated urine (urine specific gravity ≥1.021), an indicator of hypohydration, across Tsimane' hunter-forager-horticulturalists living in hot-humid lowland Bolivia and Daasanach agropastoralists living in hot-arid Northern Kenya. It tested the hypotheses that household water and food insecurity would be associated with higher odds of hypohydration.

METHODS

This study collected spot urine samples and corresponding weather data along with data on household water and food insecurity, demographics, and health characteristics among 266 Tsimane' households (N = 224 men, 235 women, 219 children) and 136 Daasanach households (N = 107 men, 120 women, 102 children).

RESULTS

The prevalence of hypohydration among Tsimane' men (50.0%) and women (54.0%) was substantially higher (P < .001) than for Daasanach men (15.9%) and women (17.5%); the prevalence of hypohydration among Tsimane' (37.0%) and Daasanach (31.4%) children was not significantly different (P = .33). Multiple logistic regression models suggested positive but not statistically significant trends between household water insecurity and odds of hypohydration within populations, yet some significant joint effects of water and food insecurity were observed. Heat index (2°C) was associated with a 23% (95% confidence interval [CI]: 1.09-1.40, P = .001), 34% (95% CI: 1.18-1.53, P < .0005), and 23% (95% CI: 1.04-1.44, P = .01) higher odds of hypohydration among Tsimane' men, women, and children, respectively, and a 48% (95% CI: 1.02-2.15, P = .04) increase in the odds among Daasanach women. Lactation status was also associated with hypohydration among Tsimane' women (odds ratio = 3.35, 95% CI: 1.62-6.95, P = .001).

CONCLUSION

These results suggest that heat stress and reproductive status may have a greater impact on hydration status than water insecurity across diverse ecological contexts.

High-fat diet alters fluid intake without reducing sensitivity to glucagon-like peptide-1 receptor agonist effects

Rats that are maintained on a high-fat diet (HFD) differ from controls in many ways, but how HFD maintenance affects water intake and drinking behavior has not been well studied. This is unfortunate because diet and obesity may influence fluid balance in humans through a mechanism that is poorly understood. We therefore tested the hypothesis that HFD maintenance affects water intake in rats. Water intake and drinking behavior are, in part, controlled by the actions of glucagon-like peptide-1 (GLP-1), a peptide which is well studied for its hypophagic effects. Previous studies have shown that HFD maintenance impairs the ability of GLP-1 receptor agonists to suppress food intake when the drug is administered peripherally, but not centrally. The effects of GLP-1 on fluid intake are thought to rely more on central receptor activation; therefore, a secondary aim of these experiments was to shed additional light on the location of GLP-1 responsive cells that mediate feeding vs drinking behavior. We maintained male Sprague-Dawley rats on HFD or low-fat diet (LFD) for six weeks and measured body weight, food intake, water intake, and drinking behavior. We then tested the relative contributions of diet and body weight on food intake and water intake after peripheral and central injections of GLP-1 receptor agonist Exendin-4 (Ex4). We found that HFD maintenance reduced the amount of water consumed, when intake was corrected for body weight. Consistent with other reports, rats on HFD showed a smaller suppression of food intake when given Ex4 peripherally, but not centrally. Water intake suppression when given Ex4 did not differ by diet or body weight regardless of injection site, however, adding support to the hypothesis that only central GLP-1 receptors are involved in water intake.

Systematic Investigation of the Effects of Long-Term Administration of a High-Fat Diet on Drug Transporters in the Mouse Liver, Kidney and Intestine

BACKGROUND

Long-term intake of a high-fat diet is a crucial factor contributing to obesity, which has become a global public health problem. Progressive obesity subsequently leads to hepatic injury, renal damage and intestinal atrophy. Transporters expressed in the liver, kidney and intestine play important roles in the deposition of nutrients and drugs, but researchers have not clearly determined whether/how the expression of transporters changes after long-term administration of a High-Fat Diet (HFD). This study aims to explore the effects of the long-term administration of a HFD on the expression of drug transporters in the liver, kidney and intestine in mice and to provide useful information for medical applications in the clinic.

METHODS

Male C57BL/6J mice were fed either a basal diet or HFD for 24 weeks, and oral glucose tolerance tests were performed after 3, 11 and 23 weeks. Serum was obtained to measure lipid metabolism, inflammatory mediators, renal function and hepatic function. Adipose tissues, kidney, pancreas and liver were collected for hematoxylin and eosin (H&E) staining after 4, 12 and 24 weeks. The mRNA and proteins expression of drug transporters in the liver, kidney and intestine were detected using real-time PCR and western blot, respectively.

RESULTS

Compared with the control group, long-term HFD administration significantly increased the adipose index. The serum lipid levels, including Total Cholesterol (TC), Triglyceride (TG), and Low-Density Lipoprotein Cholesterol (LDL-C), as well as the levels of the inflammatory cytokines Interleukin-10 (IL-10) and tumor necrosis factor-α (TNF-α) were significantly elevated in HFD-induced obese mice. H&E staining revealed pathological changes in the adipose cells, liver, kidney and pancreas from the obese group following the long-term administration of the HFD. The liver of the obese group presented increased mRNA expression of the efflux transporter Mrp2 and uptake transporter Oat2 at 24 weeks. The relative expression of Oat2 increased 4.08-fold and the protein expression of Oat2 was upregulated at 24 weeks in HFD-fed mice, while the mRNA expression of the uptake transporters Oct1, Oatp1b2 and Oatp1a4 decreased by 79%, 61% and 19%, respectively. The protein expression of Oct1 was significantly downregulated in obese mice at 12 weeks. The mRNA expression of the efflux transporter Mdr1a was significantly reduced in HFD-fed mice compared with the control group at 24 weeks. Western blot showed that the trend of protein level of Mdr1 was consistent with the mRNA expression. In the kidney, the level of the Oct2 mRNA increased 1.92- and 2.46-fold at 4 and 12 weeks in HFD-fed mice, respectively. The expression of the Oat1 and Oat3 mRNAs was markedly downregulated in the kidneys of mice with HFD-induced obesity at 4 weeks. The decrease of 72% and 21% in Mdr1a mRNA expression was observed in the obese model at 4 weeks and 12 weeks, respectively. Western blot showed that the protein levels of Mdr1 and Oat1 were consistent with the mRNA expression. The qPCR experiments showed a 2.87-fold increase in Bcrp mRNA expression at 24 weeks, and the expression of the Pept1 mRNA increased 2.84-fold in intestines of obese mice subjected to long-term administration of the HFD compared with control mice at 12 weeks. Western blot showed that the trend of protein levels of Mdr1 and Mrp2 were consistent with the mRNA expression.

CONCLUSION

The expression of uptake and efflux transporters mRNAs and protein levels were altered in obese mice compared with control mice, providing scientific evidence for future medical applications in the clinic.

Models of hydration and nutrition require environmental data

OBJECTIVE

To recognize the causality of environmental factors (i.e. temperature, humidity and sun exposure) on nutritional variables, specifically body water balance and water-seeking behaviour.

DESIGN

Author perspective.

SETTING

Global.

PARTICIPANTS

Not applicable.

RESULTS

A free-standing code supplement is provided to facilitate investigators in accessing meteorological data for incorporation into analyses related to nutrition and hydration.

CONCLUSIONS

Analytical models related to human hydration should account for the environment de rigueur.

Water turnover among human populations: Effects of environment and lifestyle

OBJECTIVES

To discuss the environmental and lifestyle determinants of water balance in humans and identify the gaps in current research regarding water use across populations.

METHODS

We investigated intraspecific variation in water turnover by comparing data derived from a large number of human populations measured using either dietary survey or isotope tracking. We also used published data from a broad sample of mammalian species to identify the interspecific relationship between body mass and water turnover.

RESULTS

Water facilitates nearly all physiological tasks and water turnover is strongly related to body size among mammals (r2=0.90). Within humans, however, the effect of body size is small. Instead, water intake and turnover vary with lifestyle and environmental conditions. Notably, despite living physically active lives in conditions that should increase water demands, the available measures of water intake and turnover among small-scale farming and pastoralist communities are broadly similar to those in less active, industrialized populations.

CONCLUSIONS

More work is required to better understand the environmental, behavioral, and cultural determinants of water turnover in humans living across a variety of ecosystems and lifestyles. The results of such work are made more vital by the climate crisis, which threatens the water security of millions around the globe.

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.

Biobehavioral variation in human water needs: How adaptations, early life environments, and the life course affect body water homeostasis

Body water homeostasis is critical for optimal physiological and cognitive function for humans. The majority of research has illustrated the negative biological consequences of failing to meet water needs. The human body has several mechanisms for detecting, regulating, and correcting body water deficits and excesses. However, variation exists in total water intake and how people meet those water needs as well as thirst thresholds and how well people tolerate water restriction. An evolutionary and developmental framework provides an underexplored perspective into human water needs by examining how adaptations, early life experiences and environments, as well as life course changes in health states and behaviors may shape these critical factors in body water homeostasis. This article first reviews biological and behavioral adaptations to water scarcity among animals and humans. It then examines human variation in water intake in a mostly water secure environment through the analysis of National Health and Nutrition Examination Survey dietary data and the link between water intake patterns and hydration biomarkers. Next, it reviews existing evidence of how maternal water restriction in utero and during lactation shape vasopressin release, thirst thresholds, drinking patterns, and body water homeostasis for the infant. Early life water restriction appears to have implications for hydration status, body size, and cardiovascular health. Finally, it examines how life course changes in health states and behaviors, including obesity, sleep, and parasitic infection, affect body water homeostasis. This article poses new questions about the plasticity and shaping of human water needs, thirst, and hydration behaviors.

Unexplained Variance in Hydration Study

With the collection of water-intake data, the National Health and Nutrition Examination Survey (NHANES) is becoming an increasingly popular resource for large-scale inquiry into human hydration. However, are we leveraging this resource properly? We sought to identify the opportunities and limitations inherent in hydration-related inquiry within a commonly studied database of hydration and nutrition. We also sought to critically review models published from this dataset. We reproduced two models published from the NHANES dataset, assessing the goodness of fit through conventional means (proportion of variance, R²). We also assessed model sensitivity to parameter configuration. Models published from the NHANES dataset typically yielded a very low goodness of fit R² < 0.15. A reconfiguration of variables did not substantially improve model fit, and the goodness of fit of models published from the NHANES dataset may be low. Database-driven inquiry into human hydration requires the complete reporting of model diagnostics in order to fully contextualize findings. There are several emergent opportunities to potentially increase the proportion of explained variance in the NHANES dataset, including novel biomarkers, capturing situational variables (meteorology, for example), and consensus practices for adjustment of co-variates.

Cardiovascular and hidroelectrolytic changes in rats fed with high-fat diet

Obesity activates the renin-angiotensin and sympathetic systems facilitating hypertension and changes in the hydroelectrolytic balance. In the present study, in rats fed with high-fat diet (HFD), we investigated daily water intake and urinary excretion, prandial consumption of water and the changes in blood pressure and water intake to intracerebroventricular (icv) angiotensin II (ANG II). Male Holtzman rats (290-320 g) were fed with standard diet (SD, 11% calories from fat) or HFD (45% calories from fat) for 6 weeks. Part of the animals received a stainless steel cannula in the lateral ventricle (LV) at the 6th week after the beginning of the diets and the experiments were performed at the 7th week. The pressor effect, but not the dipsogenic response to acute icv injection of ANG II, was potentiated in the HFD rats. Daily water intake and urinary volume were reduced in rats fed with HFD with no significant changes in sodium excretion. Prandial water consumption was also reduced in rats ingesting HFD, an effect almost totally reverted blocking salivation with atropine. These results show a potentiation of the pressor response to icv ANG II in HFD-fed rats, without changing icv ANG II-induced water intake. In addition, prandial and daily water intake and urinary volume were reduced in HFD-fed rats, without changing sodium excretion. Salivation in rats ingesting HFD may play a role in the reduced prandial and daily water intake.

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

In 2005, US water intake recommendations were based on analyses of Nutrition Health and Examination Surveys (NHANES) III data that examined if hydration classification varied by water intake and estimated the median water intake associated with hydration in persons aged 19–30. Given the upcoming 2020–2025 Dietary Guidelines review, this analysis addressed the same two aims with 2009–2012 NHANES data. Methods were updated by defining hydration criteria in terms of multiple measures (serum sodium 135–144 mmol/L and urine osmolality < 500 mmol/kg), expressing water intake as ml/kg, distinguishing plain water intake (PWI) from total water intake (TWI), using weighted age- and sex-specific multivariable models to control for determinants of water intake requirements, and selecting two study samples (the non-acutely ill US population and a sub-group without selected chronic disease risk factors). In the US population and sub-group, the relative risk (RR) of meeting the hydration criteria was significantly greater for individuals with TWI ≥ 45 mL/kg or PWI ≥ 20 mL/kg (for the US population 19–50 years of age: adjusted RR = 1.36, 95% CI: 1.10–1.68 for males; adjusted RR = 1.70, 95% CI: 1.49–1.95 for females. For the sub-group 51–70 years of age: adjusted RR = 2.20, 95% CI: 1.15–4.18 for males; adjusted RR = 2.00, 95% CI: 1.18–3.40 for females). The median (SE) TWI and PWI associated with meeting the hydration criteria for males and females 19–50 years of age were 42 (2) mL/kg and 14 (1) mL/kg and 43 (2) mL/kg and 16 (1) mL/kg, respectively. The significant association between water intake and hydration classification differs from the null association underlying the 2005 water intake recommendations and may lead to different reasoning and inferences for the 2020–2025 Dietary Guidelines.

Secondary data analysis to answer questions in human biology

Despite a growing number of publicly available datasets, the use of these datasets for secondary analyses in human biology is less common compared with other fields. Secondary analysis of existing data offers an opportunity for human biologists to ask unique questions through an evolutionary and biocultural lens, allowing for an analysis of cultural and structural nuances that affect health. Leveraging publicly available datasets for human biology research is a way for students and established researchers to complement their data collection, use existing data for master's and doctoral theses, pilot test questions, and use existing data to answer interesting new questions or explore questions at the population level. Here we describe where publicly available data are stored, highlighting some data repositories and how to access them. We then discuss how to decide which dataset is right, depending on the research question. Next, we describe steps to construct datasets, analytical considerations and methodological challenges, best practices, and limitations depending on the structure of the study. We close by highlighting a number of publicly available datasets that have been used by human biologists and other datasets that may be of interest to the community, including research that has been conducted on some example datasets.

Child and Adolescent Sugar-Sweetened Beverage Intakes Are Longitudinally Associated with Higher Body Mass Index z Scores in a Birth Cohort Followed 17 Years

BACKGROUND

Sugar-sweetened beverages (SSB) are considered a risk factor for obesity.

OBJECTIVE

The objective of the current study was to investigate associations between the predictors of beverage and energy intakes and mean adequacy ratios (MARs), and the outcome of body mass index (BMI) z scores, in a birth cohort using longitudinal models.

DESIGN

This was a longitudinal analysis of secondary data.

PARTICIPANTS/SETTING

Participants in the Iowa Fluoride and Iowa Bone Development Studies with two beverage intake questionnaires completed between ages 2 and 4.7 years or 5 and 8.5 years or one questionnaire between ages 9 and 10.5, 11 and 12.5, 13 and 14.5, or 15 and 17 years (n=720); two food and beverage diaries completed between ages 2 and 4.7 years or 5 and 8.5 years or completion of the Block's Kids' Food Frequency Questionnaires at age 11, 13, 15, or 17 years (n=623); and anthropometric measures at the corresponding age 5-, 9-, 11-, 13-, 15-, or 17-year examination(s).

PREDICTORS

Mean daily 100% juice, milk, SSB, water/sugar-free beverage, and energy intakes and MARs averaged over ages 2 to 4.7, 5 to 8.5, 9 to 10.5, 11 to 12.5, 13 to 14.5, or 15 to 17 years were predictors.

OUTCOME

BMI z score was the outcome.

STATISTICAL ANALYSES

Linear mixed models were fit for each beverage, energy, and MAR variable, with the beverage, energy, or MAR variable as the predictor and BMI z score as the outcome. Beverage models were adjusted for energy and MAR and baseline socioeconomic status.

RESULTS

SSB intake adjusted for energy intake, MAR, and baseline socioeconomic status was associated with BMI z score; each additional 8 oz SSB consumed/day throughout childhood and adolescence increased the BMI z score an average 0.050 units (95% CI 0.022 to 0.079; P=0.001). Adjusted water/sugar-free beverage intake (0.026 units; 95% CI 0.006 to 0.046; P=0.013) was modestly associated with BMI z score, while 100% juice (-0.001 units; 95% CI -0.059 to 0.057; P=0.97) and milk (0.022 units; 95% CI -0.007 to 0.052; P=0.13) intakes were not associated with BMI z scores.

CONCLUSIONS

Higher SSB intakes were associated with increased BMI z scores throughout childhood and adolescence in Iowa Fluoride Study participants. Public health initiatives targeting SSB consumption during childhood and adolescence remain relevant.

Phthalate exposure and odds of bacterial vaginosis among U.S. reproductive-aged women, NHANES 2001-2004

Endocrine-disrupting chemicals, such as phthalates, are an unexamined potential risk factor for bacterial vaginosis (BV) and warrant investigation because hormones affect BV. We examined the association between phthalate exposure and BV in the National Health and Nutrition Examination Survey, 2001-2004. BV outcomes were defined as intermediate (Nugent score of 4-6) and positive (7-10). Phthalate metabolites, including monoethyl phthalate (MEP), mono-n-butyl phthalate (MnBP), and di(2-ethylhexyl) phthalate (DEHP) metabolites, were measured in urine. Among 854 women with complete data, multinomial logistic regression revealed that concentrations of MnBP (Q4 vs. Q1 OR = 3.01, 95% CI 1.76-5.15, p-trend <0.001) and ΣDEHP metabolites (Q4 OR = 2.55, 95% CI 1.45-4.47, p-trend = 0.03) were associated with Nugent-score BV, although only MnBP was significant after adjustment for confounders. Associations were null after adjustment for urinary creatinine (MnBP Q4 OR = 1.11, 95% CI 0.63-1.96; ΣDEHP Q4 OR = 0.72, 95% CI 0.37-1.39). Future work should further examine these relationships using direct measurements of intravaginal phthalates exposures.

Detection of Glycemia and Osmolarity Changes Using Eye Examinations

Background: Glycated hemoglobin (HbA1c) is an index of the average blood glucose level over the preceding 2-3 months. In experimental studies, the lens responded to changes in osmolarity by forming vacuoles. By observing the vacuoles of the lens during eye examination, can we detect changes in osmolarity and glycemia over the last 6 months through HbA1c levels? Methods: In total, 400 patients (mean age, 67.7 ± 9.8 years), including those with diabetes mellitus, hypertension, and heart failure, were included in the study. The control group contained 70 patients matched in terms of age and sex and who had no prior disease (mean age, 67.8 ± 9.4 years). Monthly Na, glucose, and blood urea nitrogen values were used to calculate changes in osmolarity over 6 months. HbA1c values were also recorded. Biomicroscopy was used to evaluate lens vacuolation; all vacuoles were digitally photographed and converted to ImageJ format. Results: The sensitivity and specificity of using large vacuoles to detect HbA1c ≥10% were 88.0% (95% confidence interval [CI]: 68.8-97.4) and 82.6% (95% CI: 74.1-89.2), respectively. The sensitivity and specificity of detecting a 10 mOsm/kg change in osmolarity were 61% (95% CI: 48.9-72.4) and 94.5% (95% CI: 91.5-96.7), respectively. Conclusions: Lens vacuoles, which can be observed with a simple and quick examination, can be used to detect HbA1c levels and osmolarity changes over the last 6 months. Because of their relationship to the severity of retinopathy, vacuoles can also be used as a weak control indicator.

Schistosomiasis and hydration status: Schistosoma haematobium, but not Schistosoma mansoni increases urine specific gravity among rural Tanzanian women

OBJECTIVES

Schistosome infections can damage organs important for water homeostasis, especially the kidneys. Urogenital schistosomiasis (caused by Schistosoma haematobium) increases protein and blood in urine and intestinal schistosomiasis (caused by S. mansoni) affects total body water. However, no data exist on how different schistosome species affect urine specific gravity (USG), a hydration biomarker. Therefore, we assessed the relationship between S. haematobium- and S. mansoni-infected and uninfected women and USG in rural Tanzania.

MATERIALS AND METHODS

Surveys were conducted and stool and urine samples were collected among 211 nonpregnant women aged 18-50. S. haematobium eggs were detected using the urine filtration method. S. mansoni eggs were detected using the Kato Katz method. USG was measured using a refractometer and analyzed as both a continuous and dichotomous variable. Regression (linear/logistic) models were estimated to test the relationship between infection and hydration status.

RESULTS

The prevalence of S. haematobium was 5.9% and S. mansoni was 5.4% with no coinfections. In regression models, S. haematobium-infected women had significantly higher USG (Beta = 0.007 g mL^-1 ; standard error = 0.002; p = 0.001) and odds (Odds ratio: 7.76, 95% CI: 1.21-49.5) of elevated USG (>1.020 g mL^-1 ) than uninfected women, whereas S. mansoni-infected women did not.

DISCUSSION

Schistosoma haematobium, but not S. mansoni, infection is associated with higher USG and risk of inadequate hydration. Future work should determine whether findings are attributable to parasite-induced debris in urine or urinary tract pathologies and signs of renal damage. Human and non-human primate studies using USG in schistosome-endemic areas should account for schistosomiasis.

Cross-sectional association of dietary water intakes and sources, and adiposity: National Adult Nutrition Survey, the Republic of Ireland

Purpose

Drinking (plain) water intake has been associated with weight loss and reducing energy intake in intervention trials. In free-living populations, replacing other beverages with drinking water is associated with reduced obesity risk. However, the association of total water intake and its sources, and body fat distribution remain unevaluated. Thus, the aim of this study was to investigate total water intake and its sources and the association with anthropometric measures.

Methods

Cross-sectional study of 1500 adults aged 18–90 years (Irish National Adult Nutrition Survey, 2008–2010). Total water intake and its sources were estimated using food records. Associations of total water, drinking water, beverage moisture and food moisture intakes split by tertile, and BMI (kg/m²), waist circumference (cm), and bio-impedance derived body fat (%) were evaluated using covariate-adjusted linear regression analyses including adjustment for energy intake and energy expenditure.

Results

Higher consumption of total water was associated with lower waist circumference [β-coefficient (95% CI), p trend, tertile 3 versus tertile 1: − 2.19 (− 4.06, − 0.32), 0.036], but not BMI [− 0.44 (− 1.16, 0.28), 0.336] or body fat [− 0.87 (− 1.91, 0.17), 0.146]. Higher consumption of drinking water and food moisture were associated with lower BMI [− 0.65 (− 1.30, − 0.01), 0.027; − 0.64 (− 1.41, − 0.13), 0.014, respectively], body fat [− 1.51 (− 2.43, − 0.59), 0.001; − 1.00 (− 2.12, − 0.12), 0.001], and waist circumference [− 2.83 (− 4.51, − 1.16), < 0.001; − 1.84 (− 3.86, − 0.19), 0.082]. Beverage moisture was not associated with any of the anthropometric measurements.

Conclusions

Consumption of drinking water and food moisture and not total water or beverage moisture were inversely associated with adiposity, independent of energy intake and expenditure. Advice encouraging drinking water and food moisture intake may be beneficial in addition to energy balance advice, in combating obesity.

Electronic supplementary material

The online version of this article (10.1007/s00394-018-1635-z) contains supplementary material, which is available to authorized users.

Hydration and obesity among outpatient-based population: H2Ob study

Recent evidence suggests that obese people are hypohydrated and that water consumption may be a useful indicator for the prevention and treatment of obesity. Nevertheless, there is no agreement regarding the best hydration status indicators and there are few data about the relationship between hydration and body weight. In the present study, we aim to analyze the correlation among hydration status with obesity measured by three different methods (plasma osmolarity, urinary specific gravity (USG) and urinary osmolarity) in a hospital-based outpatient population. We have carried out a cross-sectional study to evaluate the association between obesity and hydration status in 260 patients, average 56.5±15.7 years. Hydration status was estimated by means of plasma osmolarity, urine osmolarity and USG. We did show significant trend of higher urine osmolarity (P=0.03), USG (P=0.000) and plasma osmolarity (P=0.000) with an increase of weight status categories, more accurate in the case of plasma osmolarity. In a multivariate analysis, after controlled by confounders, we found that obesity was associated with plasma osmolarity (OR 1.09; 95% CI 1.02 to 1.17, P=0.009), urine osmolarity (OR 1.00; 95% CI 1.00 to 1.01, P=0.05) and USG (OR 1.02; 95% CI 1.00 to 1.04, P=0.05). Our results have shown a more accurate relationship between plasma osmolarity with all body mass index categories. This finding may have clinical implications that must be confirmed in further studies.

Hyaluronan Production by Renomedullary Interstitial Cells: Influence of Endothelin, Angiotensin II and Vasopressin

The content of hyaluronan (HA) in the interstitium of the renal medulla changes in relation to body hydration status. We investigated if hormones of central importance for body fluid homeostasis affect HA production by renomedullary interstitial cells in culture (RMICs). Simultaneous treatment with vasopressin and angiotensin II (Ang II) reduced HA by 69%. No change occurred in the mRNA expressions of hyaluronan synthase 2 (HAS2) or hyaluronidases (Hyals), while Hyal activity in the supernatant increased by 67% and CD44 expression reduced by 42%. The autocoid endothelin (ET-1) at low concentrations (10⁻¹⁰ and 10⁻⁸ M) increased HA 3-fold. On the contrary, at a high concentration (10⁻⁶ M) ET-1 reduced HA by 47%. The ET-A receptor antagonist BQ123 not only reversed the reducing effect of high ET-1 on HA, but elevated it to the same level as low concentration ET-1, suggesting separate regulating roles for ET-A and ET-B receptors. This was corroborated by the addition of ET-B receptor antagonist BQ788 to low concentration ET-1, which abolished the HA increase. HAS2 and Hyal2 mRNA did not alter, while Hyal1 mRNA was increased at all ET-1 concentrations tested. Hyal activity was elevated the most by high ET-1 concentration, and blockade of ET-A receptors by BQ123 prevented about 30% of this response. The present study demonstrates an important regulatory influence of hormones involved in body fluid balance on HA handling by RMICs, thereby supporting the concept of a dynamic involvement of interstitial HA in renal fluid handling.

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

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

Arsenic and Obesity: A Comparison of Urine Dilution Adjustment Methods

INTRODUCTION

A commonly used approach to adjust for urine dilution in analyses of biomarkers is to adjust for urinary creatinine. However, creatinine is a product of muscle mass and is therefore associated with body mass. In studies of urinary analytes and obesity or obesity-related outcomes, controlling for creatinine could induce collider stratification bias. We illustrate this phenomenon with an analysis of urinary arsenic.

OBJECTIVE

We aimed to evaluate various approaches of adjustment for urinary dilution on the associations between urinary arsenic concentration and measures of obesity.

METHODS

Using data from the National Health and Nutrition Examination Survey, we regressed body mass index (BMI) and waist-to-height ratios on urinary arsenic concentrations. We compared eight approaches to account for urine dilution, including standardization by urinary creatinine, osmolality, and flow rates, and inclusion of these metrics as independent covariates. We also used a recently proposed method known as covariate-adjusted standardization.

RESULTS

Inverse associations between urinary arsenic concentration with BMI and waist-to-height ratio were observed when either creatinine or osmolality were used to standardize or as covariates. Not adjusting for dilution, standardizing or adjusting for urinary flow rate, and using covariate-adjusted standardization resulted in null associations observed between arsenic concentration in relation to BMI and waist-to-height ratio.

CONCLUSIONS

Our findings suggest that arsenic exposure is not associated with obesity, and that urinary creatinine and osmolality may be colliders on the causal pathway from arsenic exposure to obesity, as common descendants of hydration and body composition. In studies of urinary biomarkers and obesity or obesity-related outcomes, alternative metrics such as urinary flow rate or analytic strategies such as covariate-adjusted standardization should be considered. https://doi.org/10.1289/EHP1202.

Racial/Ethnic and Socioeconomic Disparities in Hydration Status Among US Adults and the Role of Tap Water and Other Beverage Intake

OBJECTIVES

To evaluate whether differences in tap water and other beverage intake explain differences in inadequate hydration among US adults by race/ethnicity and income.

METHODS

We estimated the prevalence of inadequate hydration (urine osmolality ≥ 800 mOsm/kg) by race/ethnicity and income of 8258 participants aged 20 to 74 years in the 2009 to 2012 National Health and Nutrition Examination Survey. Using multivariable regression models, we estimated associations between demographic variables, tap water intake, and inadequate hydration.

RESULTS

The prevalence of inadequate hydration among US adults was 29.5%. Non-Hispanic Blacks (adjusted odds ratio [AOR] = 1.44; 95% confidence interval [CI] = 1.17, 1.76) and Hispanics (AOR = 1.42; 95% CI = 1.21, 1.67) had a higher risk of inadequate hydration than did non-Hispanic Whites. Lower-income adults had a higher risk of inadequate hydration than did higher-income adults (AOR = 1.23; 95% CI = 1.04, 1.45). Differences in tap water intake partially attenuated racial/ethnic differences in hydration status. Differences in total beverage and other fluid intake further attenuated sociodemographic disparities.

CONCLUSIONS

Racial/ethnic and socioeconomic disparities in inadequate hydration among US adults are related to differences in tap water and other beverage intake. Policy action is needed to ensure equitable access to healthy beverages.