Inadequate Hydration, BMI, and Obesity Among US Adults: NHANES 2009–2012
Chang, T., MD, MPH, MS, et.al., Annals of Family Medicine, 14(4):320-324, July 2016
Improving hydration is a strategy commonly used by clinicians to prevent overeating with the goal of promoting a healthy weight among patients. The relationship between weight status and hydration, however, is unclear. Our objective was to assess the relationship between inadequate hydration and BMI and inadequate hydration and obesity among adults in the United States. Our study used a nationally representative sample from the National Health and Nutrition Examination Survey (NHANES) 2009 to 2012, and included adults aged 18 to 64 years. The primary outcome of interest was body mass index (BMI), measured in continuous values and also categorized as obese (BMI ≥30) or not (BMI <30). Individuals with urine osmolality values of 800 mOsm/ kg or greater were considered to be inadequately hydrated. Linear and logistic regressions were performed with continuous BMI and obesity status as the outcomes, respectively. Models were adjusted for known confounders including age, race/ethnicity, sex, and income-to-poverty ratio. In this nationally representative sample (n=9,528; weighted n=193.7 million), 50.8% were women, 64.5% were non-Hispanic white, and the mean age was 41 years. Mean urine osmolality was 631.4 mOsm/kg (SD=236.2 mOsm/kg); 32.6% of the sample was inadequately hydrated. In adjusted models, adults who were inadequately hydrated had higher BMIs (1.32 kg/m2; 95% CI, 0.85-1.79; P <.001) and higher odds of being obese (OR=1.59; 95% CI, 1.35- 1.88; P <.001) compared with hydrated adults. We found a significant association between inadequate hydration and elevated BMI and inadequate hydration and obesity, even after controlling for confounders. This relationship has not previously been shown on a population level and suggests that water, an essential nutrient, may deserve greater focus in weight management research and clinical strategies.
Prevention of Childhood Lead Toxicity
Council on Environmental Health, Pediatrics, June 2016
Blood lead concentrations have decreased dramatically in US children over the past 4 decades, but too many children still live in housing with deteriorated lead-based paint and are at risk for lead exposure with resulting lead-associated cognitive impairment and behavioral problems. Evidence continues to accrue that commonly encountered blood lead concentrations, even those below 5 µg/dL (50 ppb), impair cognition; there is no identified threshold or safe level of lead in blood. From 2007 to 2010, approximately 2.6% of preschool children in the United States had a blood lead concentration ≥5 µg/dL (≥50 ppb), which represents about 535 000 US children 1 to 5 years of age. Evidence-based guidance is available for managing increased lead exposure in children, and reducing sources of lead in the environment, including lead in housing, soil, water, and consumer products, has been shown to be cost-beneficial. Primary prevention should be the focus of policy on childhood lead toxicity.
Hydration and Chronic Kidney Disease Progression: A Critical Review of the Evidence
Clark, W.F., et.al., American Journal of Nephrology, 43(4):281-292, May 2016
We performed a comprehensive literature review to examine evidence on the effects of hydration on the kidney. By reducing vasopressin secretion, increasing water intake may have a beneficial effect on renal function in patients with all forms of chronic kidney disease (CKD) and in those at risk of CKD. This potential benefit may be greater when the kidney is still able to concentrate urine (high fluid intake is contraindicated in dialysis-dependent patients). Increasing water intake is a well-accepted method for preventing renal calculi, and current evidence suggests that recurrent dehydration and heat stress from extreme occupational conditions is the most probable cause of an ongoing CKD epidemic in Mesoamerica. In polycystic kidney disease (PKD), increased water intake has been shown to slow renal cyst growth in animals via direct vasopressin suppression, and pharmacologic blockade of renal vasopressin-V2 receptors has been shown to slow cyst growth in patients. However, larger clinical trials are needed to determine if supplemental water can safely slow the loss of kidney function in PKD patients.
Effect of a School-Based Water Intervention on Child Body Mass Index and Obesity. – PubMed – NCBI
Schwartz, A.E., et al., JAMA Pediatrics, March 2016
We want to decrease the amount of caloric beverages consumed while simultaneously increasing water consumption in order to promote child health and decrease the prevalence of childhood obesity. This aim of this study is to estimate the impact of water jets (electrically cooled, large clear jugs with a push lever for fast dispensing) on standardized body mass index, overweight, and obesity in elementary school and middle school students. Milk purchases were explored as a potential mechanism for weight outcomes. This quasi-experimental study used a school-level database of cafeteria equipment deliveries between the 2008-2009 and 2012-2013 and included a sample of 1227 New York, New York, public elementary schools and middle schools and the 1 065 562 students within those schools. The intervention was installation of water jets in schools. Individual body mass index (BMI) was calculated for all students in the sample using annual student-level height and weight measurements collected as part of New York’s FITNESSGRAM initiative. Age- and sex-specific growth charts produced by the Centers for Disease Control and Prevention were used to categorize students as overweight and obese. The hypothesis that water jets would be associated with decreased standardized BMI, overweight, and obesity was tested using a difference-in-difference strategy, comparing outcomes for treated and nontreated students before and after the introduction of a water jet. This study included 1 065 562 students within New York City public elementary schools and middle schools. There was a significant effect of water jets on standardized BMI, such that the adoption of water jets was associated with a 0.025 (95% CI, -0.038 to -0.011) reduction of standardized BMI for boys and a 0.022 (95% CI, -0.035 to -0.008) reduction of standardized BMI for girls (P < .01). There was also a significant effect on being overweight. Water jets were associated with a 0.9 percentage point reduction (95% CI, 0.015-0.003) in the likelihood of being overweight for boys and a 0.6 percentage reduction (95% CI, 0.011-0.000) in the likelihood of being overweight for girls (P < .05). We also found a 12.3 decrease (95% CI, -19.371 to -5.204) in the number of all types of milk half-pints purchased per student per year (P < .01). Results from this study show an association between a relatively low-cost water availability intervention and decreased student weight. Milk purchases were explored as a potential mechanism. Additional research is needed to examine potential mechanisms for decreased student weight, including reduced milk taking, as well as assessing impacts on longer-term outcomes.
Plain water consumption in relation to energy intake and diet quality among US adults, 2005–2012 – An – 2016 – Journal of Human Nutrition and Dietetics – Wiley Online Library
An, R. and McCaffrey, J., Journal of Human Nutrition and Dietetics, February 2016
The present study examined plain water consumption in relation to energy intake and diet quality among US adults. A nationally representative sample of 18 311 adults aged ≥18 years, from the National Health and Nutrition Examination Survey 2005–2012, was analysed. The first-difference estimator approach addressed confounding bias from time-invariant unobservables (e.g. eating habits, taste preferences) by using within-individual variations in diet and plain water consumption between two nonconsecutive 24-h dietary recalls. One percentage point increase in the proportion of daily plain water in total dietary water consumption was associated with a reduction in mean (95% confidence interval) daily total energy intake of 8.58 (7.87–9.29) kcal, energy intake from sugar-sweetened beverages of 1.43 (1.27–1.59) kcal, energy intake from discretionary foods of 0.88 (0.44–1.32) kcal, total fat intake of 0.21 (0.17–0.25) g, saturated fat intake of 0.07 (0.06–0.09) g, sugar intake of 0.74 (0.67–0.82) g, sodium intake of 9.80 (8.20–11.39) mg and cholesterol intake of 0.88 (0.64–1.13) g. The effects of plain water intake on diet were similar across race/ethnicity, education attainment, income level and body weight status, whereas they were larger among males and young/middle-aged adults than among females and older adults, respectively. Daily overall diet quality measured by the Healthy Eating Index-2010 was not found to be associated with the proportion of daily plain water in total dietary water consumption. It was concluded that promoting plain water intake could be a useful public health strategy for reducing energy and targeted nutrient consumption in US adults, which warrants confirmation in future controlled interventions.
Higher plain water intake is associated with lower type 2 diabetes risk: a cross-sectional study in humans
Carroll, H.A., et.al., Nutrition Research, 35(10):865-872, October 2015
The aim of this study was to investigate the relationship between plain water intake and type 2 diabetes (T2D) risk. It was hypothesized that higher plain water intake would be associated with a lower T2D risk score. One hundred thirty-eight adults from Southwest and Southeast England answered a cross-sectional online survey assessing T2D risk (using the Diabetes UK risk assessment); physical activity (using the short International Physical Activity Questionnaire); and consumption of fruits, vegetables, and beverages (using an adapted version of the Cambridge European Prospective Investigation into Cancer and Nutrition Food Frequency Questionnaire). There was a trend for differences in mean plain water intake between those stratified as having low, increased, moderate, or high risk of T2D; but these did not achieve significance (P = .084). However, plain water intake was significantly negatively correlated with T2D risk score (τ = -0°180, P = .005); and for every 240-mL cup of water consumed per day, T2D risk score was reduced by 0.72 point (range, 0-47) (B = -0.03, 95% confidence interval = -0.06 to -0.01, P = .014). The current study has provided preliminary results that are supported by theory; mechanisms need to be explored further to determine the true effect of plain water intake on disease risk. As increasing plain water intake is a simple and cost-effective dietary modification, its impact on T2D risk is important to investigate further in a randomized controlled trial. Overall, this study found that plain water intake had a significant negative correlation with T2D risk score; and regression analysis suggested that water may have a role in reducing T2D risk.
Obese children and adolescents need increased gastric volumes in order to perceive satiety
Mack, I., et.al., Obesity, 22.10:2123-2125, October 2014
In order to develop effective weight management strategies, it is important to identify factors that influence energy intake. Portion size has been discussed as one such factor. To date, most studies focusing on the relationship between portion size, energy intake, and weight have analyzed questionnaire data and 24-h records. In this study, we assessed the onset of satiety using the water-load test in normal-weight and obese children and adolescents. 60 obese and 27 normal-weight children and adolescents aged between 9 and 17 years participated in the water load test which involved drinking water for 3 min or until feeling full. The amount of water consumed was recorded. It was found that obese children and adolescents drank 20% more water until the onset of satiety when compared with normal-weight participants (478 ± 222 ml vs. 385 ± 115 ml, P < 0.05). Thus, it was concluded that obese children and adolescents need to ingest greater volumes to feel full which may predispose toward the consumption of larger portion sizes. This may easily lead to overeating if predominantly energy-dense foods are consumed. A reduction in energy-dense foods in the diet of obese children and adolescents appears to be a necessary strategy for managing body weight.
Prenatal drinking-water exposure to tetrachloroethylene and ischemic placental disease: a retrospective cohort study | Environmental Health | Full Text
Carwile, J.L., et al., Environmental Health, September 2014
Prenatal drinking water exposure to tetrachloroethylene (PCE) has been previously related to intrauterine growth restriction and stillbirth. Pathophysiologic and epidemiologic evidence linking these outcomes to certain other pregnancy complications, including placental abruption, preeclampsia, and small-for-gestational-age (SGA) (i.e., ischemic placental diseases), suggests that PCE exposure may also be associated with these events. We examined whether prenatal exposure to PCE-contaminated drinking water was associated with overall or individual ischemic placental diseases. Using a retrospective cohort design, we compared 1,091 PCE-exposed and 1,019 unexposed pregnancies from 1,766 Cape Cod, Massachusetts women. Exposure between 1969 and 1990 was estimated using water distribution system modeling software. Data on birth weight and gestational age were obtained from birth certificates; mothers self-reported pregnancy complications. Of 2,110 eligible pregnancies, 9% (N = 196) were complicated by ≥1 ischemic placental disease. PCE exposure was not associated with overall ischemic placental disease (for PCE ≥ sample median vs. no exposure, risk ratio (RR): 0.90; 95% confidence interval (CI): 0.65, 1.24), preeclampsia (RR: 0.36; 95% CI: 0.12-1.07), or SGA (RR: 0.98; 95% CI: 0.66-1.45). However, pregnancies with PCE exposure ≥ the sample median had 2.38-times the risk of stillbirth ≥27 weeks gestation (95% CI: 1.01, 5.59), and 1.35-times of the risk of placental abruption (95% CI: 0.68, 2.67) relative to unexposed pregnancies. We concluded that prenatal PCE exposure was not associated with overall ischemic placental disease, but may increase risk of stillbirth.
Sugar-Sweetened Beverage Consumption Among Adults — 18 States, 2012
Kumar, G.S., et al., CDC’s Morbidity and Mortality Weekly Report, August 2014
Reducing consumption of calories from added sugars is a recommendation of the 2010 Dietary Guidelines for Americans* and an objective of Healthy People 2020.† Sugar-sweetened beverages (SSB) are major sources of added sugars in the diets of U.S. residents (1). Daily SSB consumption is associated with obesity and other chronic health conditions, including diabetes and cardiovascular disease (2). U.S. adults consumed an estimated average of 151 kcal/day of SSB during 2009–2010, with regular (i.e., nondiet) soda and fruit drinks representing the leading sources of SSB energy intake (3,4). However, there is limited information on state-specific prevalence of SSB consumption. To assess regular soda and fruit drink consumption among adults in 18 states, CDC analyzed data from the 2012 Behavioral Risk Factor Surveillance System (BRFSS). Among the 18 states surveyed, 26.3% of adults consumed regular soda or fruit drinks or both ≥1 times daily. By state, the prevalence ranged from 20.4% to 41.4%. Overall, consumption of regular soda or fruit drinks was most common among persons aged 18‒34 years (24.5% for regular soda and 16.6% for fruit drinks), men (21.0% and 12.3%), non-Hispanic blacks (20.9% and 21.9%), and Hispanics (22.6% and 18.5%). Persons who want to reduce added sugars in their diets can decrease their consumption of foods high in added sugars such as candy, certain dairy and grain desserts, sweetened cereals, regular soda, fruit drinks, sweetened tea and coffee drinks, and other SSBs. States and health departments can collaborate with worksites and other community venues to increase access to water and other healthful beverages.
Added Sugar Intake and Cardiovascular Diseases Mortality Among US Adults | Apr 01, 2014 | JAMA Internal Medicine | JAMA Network
Yang, Q. PhD, et al., JAMA Internal Medicine, April 2014
Epidemiologic studies have suggested that higher intake of added sugar is associated with cardiovascular disease (CVD) risk factors. Few prospective studies have examined the association of added sugar intake with CVD mortality. Our objective was to examine time trends of added sugar consumption as percentage of daily calories in the United States and investigate the association of this consumption with CVD mortality. We studied the National Health and Nutrition Examination Survey (NHANES, 1988-1994 [III], 1999-2004, and 2005-2010 [n = 31 147]) for the time trend analysis and NHANES III Linked Mortality cohort (1988-2006 [n = 11 733]), a prospective cohort of a nationally representative sample of US adults for the association study. We measured cardiovascular disease mortality. We found that among US adults, the adjusted mean percentage of daily calories from added sugar increased from 15.7% (95% CI, 15.0%-16.4%) in 1988-1994 to 16.8% (16.0%-17.7%; P = .02) in 1999-2004 and decreased to 14.9% (14.2%-15.5%; P < .001) in 2005-2010. Most adults consumed 10% or more of calories from added sugar (71.4%) and approximately 10% consumed 25% or more in 2005-2010. During a median follow-up period of 14.6 years, we documented 831 CVD deaths during 163 039 person-years. Age-, sex-, and race/ethnicity–adjusted hazard ratios (HRs) of CVD mortality across quintiles of the percentage of daily calories consumed from added sugar were 1.00 (reference), 1.09 (95% CI, 1.05-1.13), 1.23 (1.12-1.34), 1.49 (1.24-1.78), and 2.43 (1.63-3.62; P < .001), respectively. After additional adjustment for sociodemographic, behavioral, and clinical characteristics, HRs were 1.00 (reference), 1.07 (1.02-1.12), 1.18 (1.06-1.31), 1.38 (1.11-1.70), and 2.03 (1.26-3.27; P = .004), respectively. Adjusted HRs were 1.30 (95% CI, 1.09-1.55) and 2.75 (1.40-5.42; P = .004), respectively, comparing participants who consumed 10.0% to 24.9% or 25.0% or more calories from added sugar with those who consumed less than 10.0% of calories from added sugar. These findings were largely consistent across age group, sex, race/ethnicity (except among non-Hispanic blacks), educational attainment, physical activity, health eating index, and body mass index. We concluded that most US adults consume more added sugar than is recommended for a healthy diet. We observed a significant relationship between added sugar consumption and increased risk for CVD mortality.
Water and beverage consumption among adults in the United States: cross-sectional study using data from NHANES 2005–2010
Drewnowski, A., et. al., BMC Public Health, November 2013
Few studies have examined plain water consumption among US adults. This study evaluated the consumption of plain water (tap and bottled) and total water among US adults by age group (20-50y, 51-70y, and ≥71y), gender, income-to-poverty ratio, and race/ethnicity. Data from up to two non-consecutive 24-hour recalls from the 2005–2006, 2007–2008 and 2009–2010 National Health and Nutrition Examination Survey (NHANES) was used to evaluate usual intake of water and water as a beverage among 15,702 US adults. The contribution of different beverage types (e.g., water as a beverage [tap or bottled], milk [including flavored], 100% fruit juice, soda/soft drinks [regular and diet], fruit drinks, sports/energy drinks, coffee, tea, and alcoholic beverages) to total water and energy intakes was examined. Total water intakes from plain water, beverages, and food were compared to the Adequate Intake (AI) values from the US Dietary Reference Intakes (DRI). Total water volume per 1,000 kcal was also examined.Water and other beverages contributed 75-84% of dietary water, with 17-25% provided by water in foods, depending on age. Plain water, from tap or bottled sources, contributed 30-37% of total dietary water. Overall, 56% of drinking water volume was from tap water while bottled water provided 44%. Older adults (≥71y) consumed much less bottled water than younger adults. Non-Hispanic whites consumed the most tap water, whereas Mexican-Americans consumed the most bottled water. Plain water consumption (bottled and tap) tended to be associated with higher incomes. On average, younger adults exceeded or came close to satisfying the DRIs for water. Older men and women failed to meet the Institute of Medicine (IOM) AI values, with a shortfall in daily water intakes of 1218 mL and 603 mL respectively. Eighty-three percent of women and 95% of men ≥71y failed to meet the IOM AI values for water. However, average water volume per 1,000 kcal was 1.2-1.4 L/1,000 kcal for most population sub-groups, higher than suggested levels of 1.0 L/1.000 kcal. It was concluded that water intakes below IOM-recommended levels may be a cause for concern, especially for older adults.
Water and beverage consumption among children age 4-13y in the United States: analyses of 2005–2010 NHANES data
Drewnowski, A., Rehm, C., and Constant, F., Nutrition Journal, June 2013
Few studies have examined water consumption patterns among US children. Additionally, recent data on total water consumption as it relates to the Dietary Reference Intakes (DRI) are lacking. This study evaluated the consumption of plain water (tap and bottled) and other beverages among US children by age group, gender, income-to-poverty ratio, and race/ethnicity. Comparisons were made to DRI values for water consumption from all sources. Data from two non-consecutive 24-hour recalls from 3 cycles of NHANES (2005–2006, 2007–2008 and 2009–2010) were used to assess water and beverage consumption among 4,766 children age 4-13y. Beverages were classified into 9 groups: water (tap and bottled), plain and flavored milk, 100% fruit juice, soda/soft drinks (regular and diet), fruit drinks, sports drinks, coffee, tea, and energy drinks. Total water intakes from plain water, beverages, and food were compared to DRIs for the US. Total water volume per 1,000 kcal was also examined. It was found that water and other beverages contributed 70-75% of dietary water, with 25-30% provided by moisture in foods, depending on age. Plain water, tap and bottled, contributed 25-30% of total dietary water. In general, tap water represented 60% of drinking water volume whereas bottled water represented 40%. Non-Hispanic white children consumed the most tap water, whereas Mexican-American children consumed the most bottled water. Plain water consumption (bottled and tap) tended to be associated with higher incomes. No group of US children came close to satisfying the DRIs for water. At least 75% of children 4-8y, 87% of girls 9-13y, and 85% of boys 9-13y did not meet DRIs for total water intake. Water volume per 1,000 kcal, another criterion of adequate hydration, was 0.85-0.95 L/1,000 kcal, short of the desirable levels of 1.0-1.5 L/1,000 kcal. It was concluded that water intakes at below-recommended levels may be a cause for concern. Data on water and beverage intake for the population and by socio-demographic group provides useful information to target interventions for increasing water intake among children.
Resolved: there is sufficient scientific evidence that decreasing sugar-sweetened beverage consumption will reduce the prevalence of obesity and obesity-related diseases
Hu, F.B., Obesity Reviews, June 2013
Sugar-sweetened beverages (SSBs) are the single largest source of added sugar and the top source of energy intake in the U.S. diet. In this review, we evaluate whether there is sufficient scientific evidence that decreasing SSB consumption will reduce the prevalence of obesity and its related diseases. Because prospective cohort studies address dietary determinants of long-term weight gain and chronic diseases, whereas randomized clinical trials (RCTs) typically evaluate short-term effects of specific interventions on weight change, both types of evidence are critical in evaluating causality. Findings from well-powered prospective cohorts have consistently shown a significant association, established temporality and demonstrated a direct dose–response relationship between SSB consumption and long-term weight gain and risk of type 2 diabetes (T2D). A recently published meta-analysis of RCTs commissioned by the World Health Organization found that decreased intake of added sugars significantly reduced body weight (0.80 kg, 95% confidence interval [CI] 0.39–1.21; P < 0.001), whereas increased sugar intake led to a comparable weight increase (0.75 kg, 0.30–1.19; P = 0.001). A parallel meta-analysis of cohort studies also found that higher intake of SSBs among children was associated with 55% (95% CI 32–82%) higher risk of being overweight or obese compared with those with lower intake. Another meta-analysis of eight prospective cohort studies found that one to two servings per day of SSB intake was associated with a 26% (95% CI 12–41%) greater risk of developing T2D compared with occasional intake (less than one serving per month). Recently, two large RCTs with a high degree of compliance provided convincing data that reducing consumption of SSBs significantly decreases weight gain and adiposity in children and adolescents. Taken together, the evidence that decreasing SSBs will decrease the risk of obesity and related diseases such as T2D is compelling. Several additional issues warrant further discussion. First, prevention of long-term weight gain through dietary changes such as limiting consumption of SSBs is more important than short-term weight loss in reducing the prevalence of obesity in the population. This is due to the fact that once an individual becomes obese, it is difficult to lose weight and keep it off. Second, we should consider the totality of evidence rather than selective pieces of evidence (e.g. from short-term RCTs only). Finally, while recognizing that the evidence of harm on health against SSBs is strong, we should avoid the trap of waiting for absolute proof before allowing public health action to be taken.
Impact of fluid intake in the prevention of urinary system diseases: a brief review
Lotan, et al., Current Opinions in Nephrology and Hypertension, Vol. 22, sup. 1, May 2013
We are often told that we should be drinking more water, but the rationale for this remains unclear and no recommendations currently exist for a healthy fluid intake supported by rigorous scientific evidence. Crucially, the same lack of evidence precludes the claim that a high fluid intake has no clinical benefit. The aim of this study is to describe the mechanisms by which chronic low fluid intake may play a crucial role in the pathologies of four key diseases of the urinary system: urolithiasis, urinary tract infection, chronic kidney disease and bladder cancer. Although primary and secondary intervention studies evaluating the impact of fluid intake are lacking, published data from observational studies appears to suggest that chronic low fluid intake may be an important factor in the pathogenesis of these diseases.
Relation between urinary hydration biomarkers and total fluid intake in healthy adults
Perrier, E., et al., European Journal of Clinical Nutrition, May 2013
In sedentary adults, hydration is mostly influenced by total fluid intake and not by sweat losses; moreover, low daily fluid intake is associated with adverse health outcomes. This study aimed to model the relation between total fluid intake and urinary hydration biomarkers. During 4 consecutive weekdays, 82 adults (age, 31.6±4.3 years; body mass index, 23.2±2.7 kg/m2; 52% female) recorded food and fluid consumed, collected one first morning urine (FMU) void and three 24-h (24hU) samples. The strength of linear association between urinary hydration biomarkers and fluid intake volume was evaluated using simple linear regression and Pearson’s correlation. Multivariate partial least squares (PLS) modeled the association between fluid intake and 24hU hydration biomarkers. Strong associations (|r|greater than or equal to0.6; P<0.001) were found between total fluid intake volume and 24hU osmolality, color, specific gravity (USG), volume and solute concentrations. Many 24hU biomarkers were collinear (osmolality versus color: r=0.49–0.76; USG versus color: r=0.46–0.78; osmolality versus USG: 0.86–0.97; P<0.001). Measures in FMU were not strongly correlated to intake. Multivariate PLS and simple linear regression using urine volume explained >50% of the variance in fluid intake volume (r2=0.59 and 0.52, respectively); however the error in both models was high and the limits of agreement very large. It was concluded that hydration biomarkers in 24hU are strongly correlated with daily total fluid intake volume in sedentary adults in free-living conditions; however, the margin of error in the present models limits the applicability of estimating fluid intake from urinary biomarkers.
Association between Water Intake, CKD, and Cardiovascular Disease: A Cross-Sectional Analysis of NHANES Data
Sontrop, et al., American Journal of Nephrology, 37:434-442, April 2013
Recent evidence from animal and human studies suggests that a higher water intake may have a protective effect on kidney function and cardiovascular disease. We wish to examine the association between water intake, chronic kidney disease and cardiovascular disease in a cross-sectional analysis of the 2005-2006 National Health and Nutrition Examination Survey Population. Total water intake from food and beverages was categorized as low – that is less than 2 litres per day, moderate – 2 to 4.3 litres per day and high – greater than 4.3 litres per day. We examined the associations between the low total water intake and chronic kidney disease and self-reported cardiovascular disease. Key Findings: Of the 3427 adults, whose mean age was 46, with a mean eGFR of 95ml/min/1.73m2, 13% had chronic kidney disease and 18% suffered cardiovascular disease. Chronic kidney disease was higher among those with the lowest (less than 2 litres of fluid per day) versus the highest total water intake (greater than 4.3 litres per day), (odds ratio 2.52, 95% confidence interval, 0.91-6.96). Once stratified by the intake of plain water and other beverages, CKD was associated with a low intake of plain water with an odds ratio of 2.36 at 95% confidence intervals of 1.1-5.06 but not other beverages. There was no association between low water intake and cardiovascular disease.
Blood pressure hyperreactivity: an early cardiovascular risk in normotensive men exposed to low-to-moderate inorganic arsenic in drinking water
Kunrath, J., et al., Journal of Hypertension, February 2013
Essential hypertension is associated with chronic exposure to high levels of inorganic arsenic in drinking water. However, early signs of risk for developing hypertension remain unclear in people exposed to chronic low-to-moderate inorganic arsenic. We evaluated cardiovascular stress reactivity and recovery in healthy, normotensive, middle-aged men living in an arsenic-endemic region of Romania. Unexposed (n = 16) and exposed (n = 19) participants were sampled from communities based on WHO limits for inorganic arsenic in drinking water (20 mmHg) and DBP (>15 mmHg). We found that drinking water inorganic arsenic averaged 40.2 ± 30.4 and 1.0 ± 0.2 μg/l for the exposed and unexposed groups, respectively (P < 0.001). Compared to the unexposed group, the exposed group expressed a greater probability of blood pressure hyperreactivity to both anticipatory stress (47.4 vs. 12.5%; P = 0.035) and cold stress (73.7 vs. 37.5%; P = 0.044). Moreover, the exposed group exhibited attenuated blood pressure recovery from stress and a greater probability of persistent hypertensive responses (47.4 vs. 12.5%; P = 0.035). We concluded inorganic arsenic exposure increased stress-induced blood pressure hyperreactivity and poor blood pressure recovery, including persistent hypertensive responses in otherwise healthy, clinically normotensive men. Drinking water containing even low-to-moderate inorganic arsenic may act as a sympathetic nervous system trigger for hypertension risk.
Water consumption, not expectancies about water consumption, affects cognitive performance in adults
Edmonds, C.J., et al., Appetite, January 2013
Research has shown that water supplementation positively affects cognitive performance in children and adults. The present study considered whether this could be a result of expectancies that individuals have about the effects of water on cognition. Forty-seven participants were recruited and told the study was examining the effects of repeated testing on cognitive performance. They were assigned either to a condition in which positive expectancies about the effects of drinking water were induced, or a control condition in which no expectancies were induced. Within these groups, approximately half were given a drink of water, while the remainder were not. Performance on a thirst scale, letter cancellation, digit span forwards and backwards and a simple reaction time task was assessed at baseline (before the drink) and 20 min and 40 min after water consumption. Effects of water, but not expectancy, were found on subjective thirst ratings and letter cancellation task performance, but not on digit span or reaction time. This suggests that water consumption effects on letter cancellation are due to the physiological effects of water, rather than expectancies about the effects of drinking water.
Changes in water and beverage intake and long-term weight changes: results from three prospective cohort studies
Pan, A., et al., International Journal of Obesity, January 2013
We aimed to examine the long-term relationship between changes in water and beverage intake and weight change. Our subjects were prospective cohort studies of 50 013 women aged 40–64 years in the Nurses’ Health Study (NHS, 1986–2006), 52 987 women aged 27–44 years in the NHS II (1991–2007) and 21 988 men aged 40–64 years in the Health Professionals Follow-up Study (1986–2006) without obesity and chronic diseases at baseline.We assessed the association of weight change within each 4-year interval, with changes in beverage intakes and other lifestyle behaviors during the same period. Multivariate linear regression with robust variance and accounting for within-person repeated measures were used to evaluate the association. Results across the three cohorts were pooled by an inverse-variance-weighted meta-analysis.We found participants gained an average of 1.45 kg (5th to 95th percentile: −1.87 to 5.46) within each 4-year period. After controlling for age, baseline body mass index and changes in other lifestyle behaviors (diet, smoking habits, exercise, alcohol, sleep duration, TV watching), each 1 cup per day increment of water intake was inversely associated with weight gain within each 4-year period (−0.13 kg; 95% confidence interval (CI): −0.17 to −0.08). The associations for other beverages were: sugar-sweetened beverages (SSBs) (0.36 kg; 95% CI: 0.24–0.48), fruit juice (0.22 kg; 95% CI: 0.15–0.28), coffee (−0.14 kg; 95% CI: −0.19 to −0.09), tea (−0.03 kg; 95% CI: −0.05 to −0.01), diet beverages (−0.10 kg; 95% CI: −0.14 to −0.06), low-fat milk (0.02 kg; 95% CI: −0.04 to 0.09) and whole milk (0.02 kg; 95% CI: −0.06 to 0.10). We estimated that replacement of 1 serving per day of SSBs by 1 cup per day of water was associated with 0.49 kg (95% CI: 0.32–0.65) less weight gain over each 4-year period, and the replacement estimate of fruit juices by water was 0.35 kg (95% CI: 0.23–0.46). Substitution of SSBs or fruit juices by other beverages (coffee, tea, diet beverages, low-fat and whole milk) were all significantly and inversely associated with weight gain. Our results suggest that increasing water intake in place of SSBs or fruit juices is associated with lower long-term weight gain.
Influence of progressive fluid restriction on mood and physiological markers of dehydration in women
Pross, N., et al., British Journal of Nutrition, 109, 313-321, January 2013
The present study evaluated, using a well-controlled dehydration protocol, the effects of 24 h fluid deprivation (FD) on selected mood and physiological parameters. In the present cross-over study, twenty healthy women (age 25 (SE 0·78) years) participated in two randomised sessions: FD-induced dehydration v. a fully hydrated control condition. In the FD period, the last water intake was between 18.00 and 19.00 hours and no beverages were allowed until 18.00 hours on the next day (23–24 h). Water intake was only permitted at fixed periods during the control condition. Physiological parameters in the urine, blood and saliva (osmolality) as well as mood and sensations (headache and thirst) were compared across the experimental conditions. Safety was monitored throughout the study. The FD protocol was effective as indicated by a significant reduction in urine output. No clinical abnormalities of biological parameters or vital signs were observed, although heart rate was increased by FD. Increased urine specific gravity, darker urine colour and increased thirst were early markers of dehydration. Interestingly, dehydration also induced a significant increase in saliva osmolality at the end of the 24 h FD period but plasma osmolality remained unchanged. The significant effects of FD on mood included decreased alertness and increased sleepiness, fatigue and confusion. The most consistent effects of mild dehydration on mood are on sleep/wake parameters. Urine specific gravity appears to be the best physiological measure of hydration status in subjects with a normal level of activity; saliva osmolality is another reliable and noninvasive method for assessing hydration status.
Hydration, Morbidity, and Mortality in Vulnerable Populations
Maughan, R.J., Nutrition Reviews, 70(2):152-155, November 2012
Both acute and chronic fluid deficits have been shown to be associated with a number of adverse health outcomes. At the extreme, deprivation of water for more than a few days inevitably leads to death, but even modest fluid deficits may precipitate adverse events, especially in young children, in the frail elderly and in those with poor health. Epidemiological studies have shown an association, although not necessarily a causal one, between a low habitual fluid intake and some chronic diseases, including urolithiasis, constipation, asthma, cardiovascular disease, diabetic hyperglycemia, and some cancers. Acute hypohydration may be a precipitating factor in a number of acute medical conditions in elderly persons. Increased mortality, especially in vulnerable populations, is commonly observed during periods of abnormally warm weather, with at least part of this effect due to failure to increase water intake, and this may have some important implications for those responsible for forward planning in healthcare facilities.
Sugar-Sweetened Beverages and Genetic Risk of Obesity
Qi, Q. PhD, et al., The New England Journal of Medicine, September 2012
Temporal increases in the consumption of sugar-sweetened beverages have paralleled the rise in obesity prevalence, but whether the intake of such beverages interacts with the genetic predisposition to adiposity is unknown. We analyzed the interaction between genetic predisposition and the intake of sugar-sweetened beverages in relation to body-mass index (BMI; the weight in kilograms divided by the square of the height in meters) and obesity risk in 6934 women from the Nurses’ Health Study (NHS) and in 4423 men from the Health Professionals Follow-up Study (HPFS) and also in a replication cohort of 21,740 women from the Women’s Genome Health Study (WGHS). The genetic-predisposition score was calculated on the basis of 32 BMI-associated loci. The intake of sugar-sweetened beverages was examined prospectively in relation to BMI. In the NHS and HPFS cohorts, the genetic association with BMI was stronger among participants with higher intake of sugar-sweetened beverages than among those with lower intake. In the combined cohorts, the increases in BMI per increment of 10 risk alleles were 1.00 for an intake of less than one serving per month, 1.12 for one to four servings per month, 1.38 for two to six servings per week, and 1.78 for one or more servings per day.
Methodological Aspects of Fluid Intake Records and Surveys
Vergne, S. PhD, Nutrition Today, July/August 2012
Assessing the fluid intake level of different populations has, to date, attracted very little interest. The comparison of existing data based on food surveys reveals notable differences between countries and within different surveys in 1 country. Methodological issues seem to account to a large extent for these differences. Recent studies conducted using specifically designed diaries to record fluid and water intake over a 7-day period tend to give more accurate results. These recent studies could potentially lead to the revision of the values of adequate intakes of water in numerous countries.
First Findings of the United Kingdom Fluid Intake Study
Gandy, J. PhD, RD, Nutrition Today, July/August 2012
Many factors influence the rising levels of obesity including changes in activity and dietary patterns. National dietary surveys are valuable tools for identifying sources of energy, including sugar, in a population. However, these surveys use diaries that aim to capture food intake rather than fluid intake and may underestimate beverage and therefore energy intakes. A study of 1456 children and adults was conducted in the United Kingdom using a 7-day fluid specific intakediary. Total daily intakes of beverages were higher in all ages compared with previous surveys. However, 30% of adults and more than 50% of children did not meet European adequate intake for total water. Children consumed on average 175 kcal/d as still or carbonated soft drinks. This fluid-specific survey raises concerns about the total and type of fluids consumed by both adults and children in the United Kingdom.
Fluids, Water, and Nutrients and the Risk of Renal Diseases: Where We Stand and a Research Agenda
Strippoli, G.F.M. MD, PhD, MPH, MM, Nutrition Today, July/August 2012
Chronic kidney disease (CKD) is a major public health challenge. Despite identification of several established cardiovascular and renal risk factors and addressing them with multiple pharmacological interventions, people with CKD continue to die, and the rate of progression of kidney disease continues to increase. In this article, we review existing evidence on the role of fluid (total fluid including fluid from water and fluid from food) and nutrient intake and the risk of kidney disease and its progression and propose a research agenda for future studies in the area. It is plausible that water and nutrient intake is an easy-to-implement strategy to reduce the risk of CKD and its progression and adverse outcomes at a population level. Cross-sectional and prospective cohort studies first and subsequently randomized trials are needed to establish the strength of association between fluid/water/nutrient intake and risk of CKD and adverse outcomes and whether a causal link exists between these exposures and the adverse outcomes.
Promotion and Provision of Drinking Water in Schools for Overweight Prevention: Randomized, Controlled Cluster Trial
Muckelbauer, R. MSc, et al., Nutrition Today, July/August 2012
The prevention of childhood overweight is a major public health challenge. Intervention trials have shown that schoolsare a promising setting for overweight prevention. To date, no particular intervention has been proved to be effective in overweight prevention. This study showed that a simple intervention with the sole focus of promoting waterconsumption effectively prevented overweight among children in elementary schools in socially deprived urban areas. The study tested whether a combined environmental and educational intervention solely promoting water consumption was effective in preventing overweight among children in elementary school. The participants in this randomized, controlled cluster trial were second- and third-graders from 32 elementary schools in socially deprived areas of 2 German cities. Water fountains were installed and teachers presented 4 prepared classroom lessons in the intervention group schools (N = 17) to promote water consumption. Control group schools (N = 15) did not receive any intervention. The prevalence of overweight (defined according to the International Obesity Task Force criteria), BMI SD scores, and beverage consumption (in glasses per day; 1 glass was defined as 200 mL) self-reported in 24-hour recall questionnaires, were determined before (baseline) and after the intervention. In addition, the water flow of the fountains was measured during the intervention period of 1 school year (August 2006 to June 2007). Data on 2950 children (intervention group: N = 1641; control group: N = 1309; age, mean ± SD: 8.3 ± 0.7 years) were analyzed. After the intervention, the risk of overweight was reduced by 31% in the intervention group, compared with the control group, with adjustment for baseline prevalence of overweight and clustering according to school. Changes in BMI SD scores did not differ between the intervention group and the control group. Water consumption after the intervention was 1.1 glasses per day greater in the intervention group. No intervention effect on juice and soft drink consumption was found. Daily water flow of the fountains indicated lasting use during the entire intervention period, but to varying extent. Our environmental and educational, school-based intervention proved to be effective in the prevention of overweight among children in elementary school, even in a population from socially deprived areas.
Abbreviations: CG—control group, CI—confidence interval, IG—intervention group, SDS—SD score
Hydration Biomarkers During Daily Life: Recent Advances and Future Potential
Armstrong, L.E. PhD, Nutrition Today, July/August 2012
Human fluid-electrolyte regulation involves multiple neuroendocrine responses to the hourly loss and gain of body water. Such dynamic complexity complicates hydration assessment and minimizes the likelihood that any single biomarker will validly and precisely describe hydration status in all life situations. This article describes the biomarkers that are currently used during daily living to assess mild dehydration, plus recent advances in our understanding of invasive and noninvasive techniques. This article also suggests directions for future exploration of novel hydration indices, in the belief that superior biomarkers exist but have not been discovered.
Hydration Status in Active Youth
Kavouras, S. A. PhD, Arnaoutis, G. PhD, Nutrition Today, July/August 2012
Fluid balance is crucial for maintaining health. It is well documented that dehydration increases physiologic strain and decreases athletic performance, especially in hot environments. Although there are numerous studies evaluating hydration status in adults, limited data concerning hydration levels in athletic youth exist. Nevertheless, most of these studies clearly indicate that (a) dehydration is a major and common problem within children exercising in the heat; and (b) children do not have the capacity to translate hydration awareness to successful hydration strategies. Further research is needed, and constant efforts must be made toward the development of more efficient hydration strategies in order to educate young people about the benefits of optimal hydration status.
Effect of a 24-Hour Fluid Deprivation on Mood and Physiological Hydration Markers in Women
Pross, N. PhD, Nutrition Today, July/August 2012
The study aim was to evaluate the effect of an acute fluid deprivation (FD) on mood and physiological parameters. Twenty healthy women (aged 25 ± 3.5 years) participated in a randomized 2-period (dehydrated vs control) crossover study. In the FD period, the last water intake was between 6 PM and 7 PM, and no fluid intake was allowed up to 6 PM on the next day. The FD resulted in increased sleepiness and fatigue, decreased alertness, and increased confusion. In this rigorously controlled protocol, the early noninvasive markers of dehydration were a reduced urine volume, increased urinary gravity, darker urine color, and increased thirst. Interestingly, dehydration also induced a significant increase in saliva osmolality at the end FD period. Plasma osmolality did not differ between experimental conditions.
Impact of Beverage Content on Health and the Kidneys
Johnson, R.J. MD, et al., Nutrition Today, July/August 2012
The last 50 years have witnessed an epidemic rise in obesity, diabetes, high blood pressure, and chronic kidney disease. Some animal research suggests the epidemic may in part be triggered by sugar. Sugar contains glucose and fructose, and studies suggest it is the fructose component that may have a role in chronic disease development. Animal studies indicate that fructose is distinct from other sugars by its ability to cause transient adenosine triphosphate (ATP) depletion in the cell with uric acid generation. The administration of fructose, or the raising of uric acid, can induce kidney disease and accelerate established kidney disease in animals. Therefore, we believe that the greatest risk from sugar is when it is given as a soft drink, as the rapidity of ingestion relates directly to the concentration of fructose that the cells are exposed to and hence govern the degree of ATP depletion and uric acid generation. Restricting sugar-sweetened beverages may be one strategy to combat obesity, diabetes, high blood pressure, and kidney disease, but human intervention studies are needed to support the theory.
Hydration: What Is Known and What Is Unknown
Rosenbloom, C. PhD RD, Nutrition Today, July/August 2012
In a 2007 article, Lawrence Armstrong of the Human Performance Institute at the University of Connecticut remarked that, when it came to assessing hydration status, we were still searching for the “elusive gold standard.” Hydration is one of those topics, like the weather, that everyone talks about but no one can make accurate predictions about. This seems to hold true for water in the form of rain… and also the water in our bodies that hydrates us. Nevertheless, athletes want to know exactly how much water they need under various exercise conditions, parents want to know if certain sugar-containing beverages will make their children obese, clinicians want to know how hydration affects chronic disease risk, and everyone wants to know if they should be carrying around a water bottle all day long! But all we can often do as nutrition scientists and exercise physiologists is to give general responses because the topic remains so “elusive.”
Hydration biomarkers and dietary fluid consumption of women
Armstrong, L., et. al. Journal of the Academy of Nutrition and Dietetics, July 2012
Normative values and confidence intervals for the hydration indices of women do not exist. Also, few publications have precisely described the fluid types and volumes that women consume. This investigation computed seven numerical reference categories for widely used hydration biomarkers (eg, serum and urine osmolality) and the dietary fluid preferences of self-reported healthy, active women. Participants (n=32; age 20±1 years; body mass 59.6±8.5 kg; body mass index [calculated as kg/m(2)] 21.1±2.4) were counseled in the methods to record daily food and fluid intake on 2 consecutive days. To reduce day-to-day body water fluctuations, participants were tested only during the placebo phase of the oral contraceptive pill pack. Euhydration was represented by the following ranges: serum osmolality=293 to 294 mOsm/kg; mean 24-hour total fluid intake=2,109 to 2,506 mL/24 hours; mean 24-hour total beverage intake=1,300 to 1,831 mL/24 hours; urine volume=951 to 1,239 mL/24 hours; urine specific gravity=1.016 to 1.020; urine osmolality=549 to 705 mOsm/kg; and urine color=5. However, only 3% of women experienced a urine specific gravity <1.005, and only 6% exhibited a urine color of 1 or 2. Water (representing 45.3% and 47.9% of 24-hour total fluid intake), tea, milk, coffee, and fruit juice were consumed in largest volumes. In conclusion, these data provide objective normative values for hyperhydration, euhydration, and dehydration that can be used by registered dietitians and clinicians to counsel women about their hydration status.
Observations of drinking water access in school food service areas before implementation of federal and state school water policy, California, 2011
Patel, A., et al., Preventing Chronic Disease, July 2012
Recent legislation requires schools to provide free drinking water in food service areas (FSAs). Our objective was to describe access to water at baseline and student water intake in school FSAs and to examine barriers to and strategies for implementation of drinking water requirements. We randomly sampled 24 California Bay Area public schools. We interviewed 1 administrator per school to assess knowledge of water legislation and barriers to and ideas for policy implementation. We observed water access and students’ intake of free water in school FSAs. Wellness policies were examined for language about water in FSAs. We found that fourteen of 24 schools offered free water in FSAs; 10 offered water via fountains, and 4 provided water through a nonfountain source. Four percent of students drank free water at lunch; intake at elementary schools (11%) was higher than at middle or junior high schools (6%) and high schools (1%). In secondary schools when water was provided by a nonfountain source, the percentage of students who drank free water doubled. Barriers to implementation of water requirements included lack of knowledge of legislation, cost, and other pressing academic concerns. No wellness policies included language about water in FSAs. We concluded that approximately half of schools offered free water in FSAs before implementation of drinking water requirements, and most met requirements through a fountain. Only 1 in 25 students drank free water in FSAs. Although schools can meet regulations through installation of fountains, more appealing water delivery systems may be necessary to increase students’ water intake at mealtimes.
French children start their school day with a hydration deficit
Bonnet, F., et al., Annals of Nutrition & Metabolism, June 2012
Fluid requirements of children vary as a function of gender and age. To our knowledge, there is very little literature on the hydration status of French children. We assessed the morning hydration status in a large sample of 529 French schoolchildren aged 9–11 years. Methods: Recruited children completed a questionnaire on fluid and food intake at breakfast and collected a urine sample the very same day after breakfast. Breakfast food and fluid nutritional composition was analyzed and urine osmolality was measured using a cryoscopic osmometer. More than a third of the children had a urine osmolality between 801 and 1,000 mosm/kg while 22.7% had a urine osmolality over 1,000 mosm/kg. This was more frequent in boys than in girls (p ! 0.001). A majority of children (73.5%) drank less than 400 ml at breakfast. Total water intake at breakfast was significantly and inversely correlated with high osmolality values. It was concluded that almost two thirds of the children in this large cohort had evidence of a hydration deficit when they went to school in the morning, despite breakfast intake. Children’s fluid intake at breakfast does not suffice to maintain an adequate hydration status for the whole morning.
Protective Nutrients: Are They Here to Stay?
Walker, W.A. MD, Heintz, K. MS, Nutrition Today, May/June 2012
Protective nutrients benefit health in various ways beyond their conventionally established nutrient function such as by enhancing immune function, promoting gastrointestinal integrity, impacting metabolism, and preventing disease. Certain of these key nutrients have taken center stage as emerging research is showing that they can play a significant role throughout the life span. Study of an infants’ first natural nutrition, breast milk, has led to an improved understanding of how different compounds can beneficially effect physiological processes and act as protective nutrients. Probiotics, or “healthy bacteria,” are living microorganisms that confer a benefit when consumed in sufficient quantities. For example, certain strains help maintain the balance of the intestinal microbiota, a complex ecosystem that can be influenced by many factors such as stress, antibiotics, and diet. Research suggests that, when the intestinal microbiota is unbalanced, overall health may be affected. Prebiotics are nondigestible carbohydrates that can be used as an energy source by certain probiotics, thereby helping them grow and flourish to further promote a healthy ecosystem. Additional nutrients such as choline, vitamin D, and omega-3 fatty acids have also gained attention as being protective beyond normal growth and development, possessing functional effects that may be vital to future recommendations for health.
Replacing caloric beverages with water or diet beverages for weight loss in adults: main results of the Choose Healthy Options Consciously Everyday (CHOICE) randomized clinical trial
Tate, D.F., et al., The American Journal of Clinical Nutrition, February 2012
Replacement of caloric beverages with noncaloric beverages may be a simple strategy for promoting modest weight reduction; however, the effectiveness of this strategy is not known. We compared the replacement of caloric beverages with water or diet beverages (DBs) as a method of weight loss over 6 mo in adults and attention controls (ACs). Results: In an intent-to-treat analysis, a significant reduction in weight and waist circumference and an improvement in systolic blood pressure were observed from 0 to 6 mo. Mean (±SEM) weight losses at 6 mo were −2.5 ± 0.45% in the DB group, −2.03 ± 0.40% in the Water group, and −1.76 ± 0.35% in the AC group; there were no significant differences between groups. The chance of achieving a 5% weight loss at 6 mo was greater in the DB group than in the AC group (OR: 2.29; 95% CI: 1.05, 5.01; P = 0.04). A significant reduction in fasting glucose at 6 mo (P = 0.019) and improved hydration at 3 (P = 0.0017) and 6 (P = 0.049) mo was observed in the Water group relative to the AC group. In a combined analysis, participants assigned to beverage replacement were 2 times as likely to have achieved a 5% weight loss (OR: 2.07; 95% CI: 1.02, 4.22; P = 0.04) than were the AC participants. Conclusions: Replacement of caloric beverages with noncaloric beverages as a weight-loss strategy resulted in average weight losses of 2% to 2.5%. This strategy could have public health significance and is a simple, straightforward message. This trial was registered at clinicaltrials.gov as NCT01017783.
Mild Dehydration Affects Mood in Healthy Young Women
Armstrong, L., et al., The Journal of Nutrition, February 2012
Limited information is available regarding the effects of mild dehydration on cognitive function. Therefore, mild dehydration was produced by intermittent moderate exercise without hyperthermia and its effects on cognitive function of women were investigated. Twenty-five females (age 23.0 ± 0.6 y) participated in three 8-h, placebo-controlled experiments involving a different hydration state each day: exercise-induced dehydration with no diuretic (DN), exercise-induced dehydration plus diuretic (DD; furosemide, 40 mg), and euhydration (EU). Cognitive performance, mood, and symptoms of dehydration were assessed during each experiment, 3 times at rest and during each of 3 exercise sessions. The DN and DD trials in which a volunteer attained a ≥1% level of dehydration were pooled and compared to that volunteer’s equivalent EU trials. Mean dehydration achieved during these DN and DD trials was −1.36 ± 0.16% of body mass. Significant adverse effects of dehydration were present at rest and during exercise for vigor-activity, fatigue-inertia, and total mood disturbance scores of the Profile of Mood States and for task difficulty, concentration, and headache as assessed by questionnaire. Most aspects of cognitive performance were not affected by dehydration. Serum osmolality, a marker of hydration, was greater in the mean of the dehydrated trials in which a ≥1% level of dehydration was achieved (P = 0.006) compared to EU. In conclusion, degraded mood, increased perception of task difficulty, lower concentration, and headache symptoms resulted from 1.36% dehydration in females. Increased emphasis on optimal hydration is warranted, especially during and after moderate exercise.
What is the cell hydration status of healthy children in the USA? Preliminary data on urine osmolality and water intake
Stookey, J.D., Brass, B., Holliday, A, Arieff, A., Public Health Nutrition, January 2012
Hyperosmotic stress on cells limits many aspects of cell function, metabolism and health. International data suggest that schoolchildren may be at risk of hyperosmotic stress on cells because of suboptimal water intake. The present study explored the cell hydration status of two samples of children in the USA. Elevated urine osmolality (>800 mmol/kg) was observed in 63 % and 66 % of participants in LA and NYC, respectively. In multivariable-adjusted logistic regression models, elevated urine osmolality was associated with not reporting intake of drinking water in the morning (LA: OR = 2·1, 95 % CI 1·2, 3·5; NYC: OR = 1·8, 95 % CI 1·0, 3·5). Although over 90 % of both samples had breakfast before giving the urine sample, 75 % did not drink water. Research is warranted to confirm these results and pursue their potential health implications.
The effects of water shortages on health and human development
Tarrass, F., and Benjelloun, M., Perspectives in Public Health, April 2011
Shortages of water could become a major obstacle to public health and development. Currently, the United Nations Children’s Fund (UNICEF) and the World Health Organization (WHO) estimate that 1.1 billion people lack access to a water supply and 2.6 billion people lack adequate sanitation. The global health burden associated with these conditions is staggering, with an estimated 1.6 million deaths every year from diseases associated with lack of access to safe drinking water, inadequate sanitation and poor hygiene. In this paper we review the impact of water shortages on health and human development.
Water, Water Everywhere… But, How Much Water Do We Really Need for Optimal Health and Wellness?
Rosenbloom, C. PhD, RD, CSSD, Nutrition Today, November/December 2010
“Water, taken in moderation, cannot hurt anybody” is a quote attributed to US author and humorist, Mark Twain. The series of articles in this special issue suggest that water in moderation may not be enough for optimal health and wellness, and the authors push the boundaries of what is currently known about water in maintaining health and preventing disease. The Hydration for Health Conference, sponsored by Danone Waters, brought together international experts to review what is known about water consumption and health or, more appropriately, what is not known about water intake and health. One of the key drivers of the interest in water and health appears to be the global obesity epidemic affecting developed and developing countries, young and old alike, but there are other health problems that might be reduced or eliminated if optimal water consumption was known and practiced.
The Mexican Experience: From Public Health Concern Toward National Beverage Guidelines
Barquera, S. MD, PhD, Nutrition Today, November/December 2010
The paper describes the process experienced in Mexico from the characterizations of beverage consumption to the development of national beverage recommendation guidelines. Mexico is one of the countries with the highest prevalence of obesity in the world. Depending on the information source, it is often ranked as second after the United States. In addition, Mexicans are the second greatest consumers of soft drinks in the world. Currently, there is some ecological evidence that associates the trends in soft-drink consumption and overall diet with the increase in the prevalence of obesity.
Healthy Hydration for Physical Activity
Péronnet, F. PhD, Nutrition Today, November/December 2010
Water is the first ingredient of life. In the comfortable environment in which we live, with an ample supply of water, we forget that our ancestors lived in an environment where water was scarce, and the weather was hot. We therefore developed a very powerful cooling system in which water plays a major role. The importance of this system is best illustrated when we are exposed to exercise and heat, separately and even more when both are combined. In these situations, the primary way to get rid of the heat generated or received from the environment is through the secretion and evaporation of sweat, which is mainly water. Thanks to this cooling system, we can sustain prolonged exposures to heat and we can work in the heat. However, if not properly replaced, fluid loss under the form of sweat results in dehydration. This reduces the ability to regulate body temperature as well as the ability to perform exercise. Under extreme circumstances, which fortunately are not often encountered, dehydration and the increase in body temperature can result in heat stroke, which could be fatal.
Understanding Fluid Consumption Patterns to Improve Healthy Hydration
Le Bellego, L. PhD, et al., Nutrition Today, November/December 2010
Water is quantitatively by far the No. 1 nutrient in our diet. Of course, this can vary, depending on the amount and the quality of food and drink one consumes, but approximately 50% of what we eat and drink every day is water (CIQUAL, Table CIQUAL 2008, composition nutritionnelle des aliments, 2008, Centre d’Information sur la Qualité des Aliments, http://www.afssa.fr/TableCIQUAL/; US Department of Agriculture, Agricultural Research Service, 2005, USDA National Nutrient Database for Standard Reference, Release 18. Nutrient Data Laboratory Home Page, http://www.nal.usda.gov/fnic/foodcomp; NUTTAB, 2006, Food Standards Australia New Zealand [FSANZ], http://www.foodstandards.gov.au/monitoringandsurveillance/nuttab2006/). It is also the No. 1 component of the human body by mass. This varies from one person to another, depending on individual characteristics such as body weight, ratio between lean and adipose tissues, and physiological state (pregnancy, etc), but approximately 60% of the adult body is composed of water. [Nutr Rev 2005;63(6 pt 2):S40-S54]. Finally, no biological reaction or function in the body would be possible without water. In other words, life is not possible without water. This makes the quantity and the quality of the fluids we have to drink every day quite an important issue both nutritionally and physiologically. From this perspective, it is interesting to discuss available recommendations for water intake and their reliability. This is very challenging, because no study is available on the long-term health effects of the quantity and/or the quality of fluids ingested.
Role of Sugar Intake in Beverages on Overweight and Health
Lafontan, M. PhD, Nutrition Today, November/December 2010
Epidemiological data have demonstrated an association between sugar intake in beverages and overweight. Cross-sectional studies are the most common but rather limited, and a lot of points are still a matter of debate. Results of intervention trials are more promising, although they remain quite rare; they provide the best arguments to infer causality. This overview is limited to the analysis of the putative impact of sugar inclusion in beverages on health, obesity, and diabetes risk. Mechanisms of action and physiological end points are highlighted to clarify the differences existing in the health impact of various kinds of sugars. When considering weight changes and obesity-related questions related to sugar-sweetened beverages consumption, it is important to take into account population differences and genetic parameters. Lifestyle influences (eg, other components of the diet and physical activity) must also be considered in the studies.
Hydration and Human Cognition
Lieberman, H.R. PhD, Nutrition Today, November/December 2010
Although adequate hydration is essential for optimal brain function, research addressing relationships between hydration status and human behavior and cognitive function is limited. The few published studies in this area are inconclusive and contradictory. The impact of variations in hydration status, which can be substantial as humans go about their daily activities, on brain function and behavior is not known and may impact quality of life. Furthermore, vulnerable populations such as children, elderly people, and individuals with illnesses may be at higher risk of degradation in cognitive function from dehydration. A variety of difficult methodological issues have impeded progress in this area. For example, there are several methods to achieve dehydration in humans, each with different strengths and weakness. Accurately assessing and modifying human hydration status and consistently achieving desired levels of dehydration in a controlled manner are problematic. It is difficult to select appropriate behavioral tasks that detect relatively subtle changes in cognitive performance and mood resulting from moderate levels of dehydration. Generating experimental designs that include hydrated control conditions and double-blind testing poses substantial challenges to investigators. Additional well-controlled research is essential if progress is to be made and understanding gained of the effects of dehydration on cognitive function. Key elements of research should include accurate methods of assessing and modifying hydration state, an adequate number of subjects, appropriate behavioral tasks to detect subtle effects of dehydration, and inclusion of rigorous control conditions.
Drinking Water and Weight Management
Stookey, J.D. PhD, Nutrition Today, November/December 2010
This review summarizes the evidence base for recommending drinking water for weight management. Crossover experiments consistently report that drinking water results in lower total energy intake when consumed instead of caloric beverages, because individuals do not eat less food to compensate for calories in beverages. Crossover experiments also consistently report that drinking water results in greater fat oxidation compared with other beverages, because drinking water does not stimulate insulin. In intervention studies, advice to drink water is associated with reduced weight gain in children and greater weight loss in dieting adults. Although gaps in knowledge remain about specific effects of drinking water on weight loss in children and obesity prevention in adults, there is a strong evidence base for recommending drinking water for weight management.
Water Physiology: Essentiality, Metabolism, and Health Implications
Kavouras, S.A. PhD, Anastasiou, C.A. PhD, Nutrition Today, November/December 2010
Water is the most abundant molecule in the human body that undergoes continuous recycling. Numerous functions have been recognized for body water, including its function as a solvent, as a means to remove metabolic heat, and as a regulator of cell volume and overall function. Tight control mechanisms have evolved for precise control of fluid balance, indicative of its biological importance. However, water is frequently overlooked as a nutrient. This article reviews the basic elements of water physiology in relation to health, placing emphasis on the assessment of water requirements and fluid balance. Current recommendations are also discussed.
Effects of Water Consumption on Kidney Function and Excretion
Tack, I., Nutrition Today, November/December 2010
Water homeostasis depends on fluid intake and maintenance of body water balance by adjustment of renal excretion under the control of arginine vasopressin hormone. The human kidney manages more efficiently fluid excess than fluid deficit. As a result, no overhydration is observed in healthy individuals drinking a large amount of fluid, whereas a mild hydration deficit is not uncommon in small-fluid-volume (SFV) drinkers. Small-fluid-volume intake does not alter renal function but is associated with an increased risk of renal lithiasis and urinary tract infection. In that case, increasing fluid intake prevents recurrence. The benefit of increasing fluid intake in healthy SFV drinkers had never been studied until now. Two recent studies from Danone Research indicate that increasing water intake in such people leads to a significant decrease of the risk of renal stone disease (assessed by measuring Tiselius’ crystallization risk index). Because renal lithiasis and urinary tract infection prevalence are quite high in western countries, this preliminary observation supports the interest of an approach based on primary prevention using voluntary increase in water-based fluid consumption in SFV drinkers. Complementary studies are required to determine other clinical impacts of SFV intake and to evaluate the benefits of increasing fluid intake.
Scientific Opinion on Dietary Reference Values for water
European Food Safety Authority (EFSA), EFSA Journal, March 2010
This Opinion of the EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA) deals with the setting of dietary reference values for water for specific age groups. Adequate Intakes (AI) have been defined derived from a combination of observed intakes in population groups with desirable osmolarity values of urine and desirable water volumes per energy unit consumed. The reference values for total water intake include water from drinking water, beverages of all kind, and from food moisture and only apply to conditions of moderate environmental temperature and moderate physical activity levels (PAL 1.6). AIs for infants in the first half of the first year of life are estimated to be 100-190 mL/kg per day. For infants 6-12 months of age a total water intake of 800-1000 mL/day is considered adequate. For the second year of life an adequate total water intake of 1100-1200 mL/day is defined by interpolation, as intake data are not available. AIs of water for children are estimated to be 1300 mL/day for boys and girls 2-3 years of age; 1600 mL/day for boys and girls 4-8 years of age; 2100 mL/day for boys 9-13 years of age; 1900 mL/day for girls 9-13 years of age. Adolescents of 14 years and older are considered as adults with respect to adequate water intake. Available data for adults permit the definition of AIs as 2.0 L/day (P 95 3.1 L) for females and 2.5 L/day (P95 4.0 L) for males. The same AIs as for adults are defined for the elderly. For pregnant women the same water intake as in non-pregnant women plus an increase in proportion to the increase in energy intake (300 mL/day) is proposed. For lactating women adequate water intakes of about 700 mL/day above the AIs of non-lactating women of the same age are derived.
Water as an essential nutrient: the physiological basis of hydration
Jéquier, E. and Constant, F., EJCN – European Journal of Clinical Nutrition, September 2009
How much water we really need depends on water functions and the mechanisms of daily water balance regulation. The aim of this review is to describe the physiology of water balance and consequently to highlight the new recommendations with regard to water requirements. Water has numerous roles in the human body. It acts as a building material; as a solvent, reaction medium and reactant; as a carrier for nutrients and waste products; in thermoregulation; and as a lubricant and shock absorber. The regulation of water balance is very precise, as a loss of 1% of body water is usually compensated within 24 h. Both water intake and water losses are controlled to reach water balance. Minute changes in plasma osmolarity are the main factors that trigger these homeostatic mechanisms. Healthy adults regulate water balance with precision, but young infants and elderly people are at greater risk of dehydration. Dehydration can affect consciousness and can induce speech incoherence, extremity weakness, hypotonia of ocular globes, orthostatic hypotension and tachycardia. Human water requirements are not based on a minimal intake because it might lead to a water deficit due to numerous factors that modify water needs (climate, physical activity, diet and so on). Water needs are based on experimentally derived intake levels that are expected to meet the nutritional adequacy of a healthy population. The regulation of water balance is essential for the maintenance of health and life. On an average, a sedentary adult should drink 1.5 l of water per day, as water is the only liquid nutrient that is really essential for body hydration.