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Hydration and Health Promotion
Abstract
While the relation between hydration status and physical activity (military operations, sports performance) has been an area of extensive research, more recently, researchers have begun examining the relation between hydration status and health, acute and chronic diseases, and cognitive performance. On November 29 and 30, 2006, the International Life Sciences Institute North America Technical Committee on Hydration organized a conference on hydration and health promotion. This article is an overview of that conference.
... In addition to adequate hydration for kidney stone prevention, fluids are required to maximize mental and physical performance. 22 For most adults, thirst and consumption of beverages at meals are adequate to maintain hydration, but experts suggest adult women need 2.7 L (11.5 cups or 91 oz) of liquid each day, with about 9 cups (72 oz) from beverages, including water. Men require about a liter more per day, about 13 cups (104 oz) from beverages. ...
... Men require about a liter more per day, about 13 cups (104 oz) from beverages. 22 Negative effects of mild dehydration on health and human performance have been reported when just 1% or 2% of body weight is lost. 22 Pross 23 reported that acute fluid deprivation, as might be experienced in daily living, negatively affects mood, sleepiness, fatigue, alertness, and vigor. ...
... 22 Negative effects of mild dehydration on health and human performance have been reported when just 1% or 2% of body weight is lost. 22 Pross 23 reported that acute fluid deprivation, as might be experienced in daily living, negatively affects mood, sleepiness, fatigue, alertness, and vigor. Exercise performance capacity and cognitive function also decline, whereas physiological strain (ie, heart rate, tissue heat storage) increases. ...
An estimated 8 to 15 million Americans perform shift work that may encourage lifestyle choices that negatively affect health. We present 2 patient cases elucidating some of the issues faced by shift workers and provide counseling strategies for changing dietary behaviors.
... That is, no one measure of blood, urine, or other signs and symptoms can accurately and reliably assess the degree of hydration. Therefore, to improve construct validity many investigators apply more than one indicator of hydration (Grandjean et al., 2000;Kolasa, Lackey, & Grandjean, 2009;Martin et al., 2006). ...
... Some investigators have investigated the sensation of thirst as a credible index of hydration (Armstrong, 2005;Kolasa et al., 2009;Scalera, 2000;Schut et al., 2005;Shirreffs et al., 2004;Vivanti, Harvey, & Ash, 2010). The DRIs mention thirst as an indicator of hydration status (IOM, 2005a). ...
... The kidneys play the most important role in water balance by controlling the rate at which water leaves the body (Robinson & Weber, 2004). The volume of loss through the kidneys can range between 0.5 liter/day (minimum or obligatory output) to upwards of 20 liter/day (maximal output) depending on the amount that is needed to maintain homeostasis (IOM, 2005a;Kolasa et al., 2009). Thus individuals who are dehydrated would output significantly less urine (in a more concentrated form) than those who are euhydrated (Sansevero, 1997). ...
The primary purpose of this study was to investigate agreement among five equations by which clinicians estimate water requirements (EWR) and to determine how well these equations predict total water intake (TWI). The Institute of Medicine has used TWI as a measure of water requirements. A secondary goal of this study was to develop practical equations to predict TWI. These equations could then be considered accurate predictors of an individual’s water requirement.
Regressions were performed to determine agreement between the five equations and between the five equations and TWI using NHANES 1999-2004. The criteria for agreement was 1) strong correlation coefficients between all comparisons and 2) regression line that was not significantly different when compared to the line of equality (x=y) i.e., the 95% CI of the slope and intercept must include one and zero, respectively. Correlations were performed to determine association between fat-free mass (FFM) and TWI. Clinically significant variables were selected to build equations for predicting TWI. All analyses were performed with SAS software and were weighted to account for the complex survey design and for oversampling.
Results showed that the five EWR equations were strongly correlated but did not agree with each other. Further, the EWR equations were all weakly associated to TWI and lacked agreement with TWI. The strongest agreement between the NRC equation and TWI explained only 8.1% of the variability of TWI. Fat-free mass was positively correlated to TWI. Two models were created to predict TWI. Both models included the variables, race/ethnicity, kcals, age, and height, but one model also included FFM and gender. The other model included BMI and osmolality. Neither model accounted for more than 28% of the variability of TWI. These results provide evidence that estimates of water requirements would vary depending upon which EWR equation was selected by the clinician. None of the existing EWR equations predicted TWI, nor could a prediction equation be created which explained a satisfactory amount of variance in TWI. A good estimate of water requirements may not be predicted by TWI. Future research should focus on using more valid measures to predict water requirements.
... To mitigate difficulties in assessing and defining dehydration, many studies employ more than one marker. This is why, in our assessment of reporting strength, we gave a higher rating to studies that included more than one assessment of hydration status, in line with suggestions that a single marker is not sufficient (Armstrong, 2012) or that two or more are optimal (Kolasa, Lackey, & Grandjean, 2009). However, whichever measure of hydration is chosen, one off measurements could be described as 'simply "snapshots" of a complex, dynamic fluid matrix' (Kolasa et al., 2009). ...
... This is why, in our assessment of reporting strength, we gave a higher rating to studies that included more than one assessment of hydration status, in line with suggestions that a single marker is not sufficient (Armstrong, 2012) or that two or more are optimal (Kolasa, Lackey, & Grandjean, 2009). However, whichever measure of hydration is chosen, one off measurements could be described as 'simply "snapshots" of a complex, dynamic fluid matrix' (Kolasa et al., 2009). It may be more appropriate to use dehdyration measurement to examine change in hydration status over time, rather than to provide an accurate picture of an individual's hydration status at a given moment. ...
Objective
: To systematically examine the effect of dehydration on health outcomes, identify associated financial costs and consider impacts on cognitive performance in older adults.
Design
: A systematic review of English-language articles via OVID using MEDLINE, PsychINFO, EMBASE, and others, to March 2018. Included studies examined the relationship between hydration status and health, care costs or cognitive outcome.
Setting
: Cross sectional and cohort data from studies reporting on dehydration in older adults.
Participants
: Adults aged 60 years and older.
Measurements
: Independent quality ratings were assessed for all extracted articles.
Results
: Of 1684 articles screened, 18 papers (N = 33,707) met inclusion criteria. Participants were recruited from hospital settings, medical long-term care centres and the community dwelling population. Data were synthesised using a narrative summary. Mortality rates were higher in dehydrated patients. Furthermore, health outcomes, including frailty, bradyarrhythmia, transient ischemic attacks, oral health and surgery recovery are linked to and worsened by dehydration. Length of hospital stay, either as a principal or secondary diagnosis, is greater in those with dehydration, compared to those who are euhydrated. Finally, neurocognitive functioning may be impacted by dehydration. There are issues with study design, inconsistency in hydration status measurement and different measures used for outcome assessment.
Conclusion
: Dehydration in older people is associated with increased mortality, poorer course of illness and increased costs for health services. In addition, there is some, but sparse evidence that dehydration in older people is linked to poorer cognitive performance. Intervention studies should test strategies for reducing dehydration in older adults.
... The change in body weight is an effective and easy method of dehydration assessment especially for measuring dehydration that occurs over a period of time (Kolasa et al. 2009), and the percentage loss of body weight equals percentage loss of body water and hence, percentage dehydration (Esievo 2017). Therefore, an accurate weight determination is perquisite to dehydration assessment using body weight. ...
... On day 0, the dogs were clinically assessed to be normal based on the absence of clinical signs suggestive of dehydration (Davis et al. 2013) and also, all clinico-pathological parameters evaluated were within normal range and were used as control to compare the observation on the other days of sampling (days 14, 21 and 28). The values agreed with the works of Saror et al. (1979) and Ihedioha et al. (2013); therefore, Decrease in body weight is an effective and easy method of dehydration assessment especially for measuring dehydration over a period of time (Kolasa et al. 2009). The observed loss of body weight which corresponds to loss of total body water and hence percentage dehydration was found to be consistent throughout the sampling period. ...
Factors that contribute to water loss in tropical animals are complex and constantly changing. To evaluate the haemato-biochemical parameters of dogs with haemorrhage-induced dehydration. A total of 12 dogs were used; haemorrhage was induced by daily removal of 10 ml of blood over a period of 28 days and analysed at the Department of Veterinary Pathology, Ahmadu Bello University (A.B.U.), Zaria, Nigeria. Dehydration was clinically assessed. Age, sex, body weight and generalised body condition of the animals were determined. Whole blood was collected for determination of haematological parameters. Serum was prepared from whole blood to determine the concentrations of urea, creatinine, total protein, albumin, glucose, sodium, calcium, chloride, phosphorus, potassium, bicarbonate, blood urea nitrogen (BUN)/creatinine ratio and anion gap (AG) as well as serum activities of liver enzymes. Reductions in body weight (1.67 kg, 2.17 kg and 3.17 kg) due to degrees of dehydration were observed on days 14, 21 and 28. Significantly higher values of packed cell volume and haemoglobin concentration (P < 0.01) due to dehydration was observed between days 0 and 14, also between days 0 and 28. Higher concentrations of urea, creatinine (P < 0.01), BUN/creatinine, total protein, albumin and urine specific gravity (P < 0.05) were observed between day 0 and days 14, 21 and 28. This study is the first to report the haemato-biochemical changes of Nigerian local dogs with haemorrhage-induced dehydration. The study did not investigate the role of type of diet on dehydration, and it is recommended that future studies should be carried out to elucidate this.
... Hydration status, which is linked to fluid consumption, is increasingly attracting attention, not only in connection with physical/sports performance (e.g., Kovacs, 2008;von Duvillard, Braun, Markofski, Beneke, & Leithäuser, 2004), but because it contributes positively to general health status and well-being (e.g. Buyckx, 2007;Kolasa, Lackey, & Grandjean, 2009). Beverage choice can also have a significant impact on nutritional status and caloric intake, for example, as an important source of micro nutrients (e.g., Calcium in milk; Committee to Review Dietary Reference Intakes for Vitamin D and Calcium, 2010) or contributing excess calories (e.g., soft drinks, fruit smoothies; Ranawana & Henry, 2010;Tuorila, Pangborn, & Schutz, 1990). ...
... Future research should extend this research to different cultural contexts preferably using representative samples. Also, this research was limited to meal-centered beverage consumption and future research should aim at providing insights on beverage consumption patterns outside of meals, where hydration could potentially play a stronger role (Kolasa et al., 2009). Future research should aim at overcoming the confound of beverage penetration and habit inherent in inter-participant correlations to provide more valid estimates of habit strength and the relative importance habit has in explaining food choice variance. ...
... Our review began with the discovery and consideration of potential medical disorders or disease types (i.e. that may be influenced by hydration status) and key search terms that involved a preliminary review of government reports (Agostoni et al., 2010;Australian National Health and Medical Research Council, 2006;Institute of Medicine USA, 2004), relevant narrative reviews, systematic reviews, meta analyses, interventional research, and observational studies (Allen et al., 2019;Armstrong, 2012;Dmitrieva et al., 2023;Enhörning et al., 2019a;Kolasa et al., 2009;Lacey et al., 2019;Manz, 2007;Manz and Wentz, 2005;Perrier et al., 2021;Popkin et al., 2010). Manual searches for relevant articles were performed within the PubMed, Embase, and Google Scholar electronic databases using advanced search operators (e.g. ...
Few previous review articles have focused on the associations between inadequate daily water intake (LOW) or urinary biomarkers of dehydration ( U D; low urine volume or high urine osmolality) and multiple diseases. Accordingly, we conducted manual online searches (47 key words) of the PubMed, Embase, and Google Scholar databases with these inclusion criteria: English language, full-text, peer reviewed, no restriction on research design, and three publications minimum. Initially, 3,903 articles were identified based on their titles and abstracts. Evaluations of full length .pdf versions identified 96 studies that were acceptable for inclusion. We concluded that the evidence is insufficient or conflicting for seven disorders or diseases (i.e. suggesting the need for additional clarifying research) and it is lacking for all-cause mortality. Differential characterizations among women and men have been reported in the results of nine studies involving five diseases. Finally, the evidence for associations of LOW or U D is strong for both kidney stones and type 2 diabetes with hyperglycemia. This suggests that great public health value (i.e. reduced disease risk) may result from increased daily water intake—a simple and cost-effective dietary modification.
... This most likely reflects the physiological slowdown in the individual brought on by fatigue and consequent self-pacing. Cognitive and physical capabilities of workers may be significantly lowered due to inadequate nutrition and fluid intake (15). Clearly this sequence of events significantly brings down the levels of productivity. ...
Background:
High process temperatures associated with industrial operations augment risk of heat stress and illness, particularly during summer months in the Gulf Region. Lack of hydration and nutrition during day time, during Ramadan can subject workers to even greater risk of heat stress and illness.
Aims:
To examine the physiological effects of prolonged fasting in thermally challenging conditions.
Methods:
Longitudinal measurements were carried out on employees during fasting in Ramadan in three departments of an aluminium smelter. After informed consent, physiological parameters were measured at 4-hour intervals.
Results:
Average heart rate and urine specific gravity increased in the first 4 hours of shift work, while tympanic temperature did not rise significantly. Moreover, in the second 4 hours of shift work, urine specific gravity stabilized compared to the first 4 hours.
Conclusions:
Robust workplace measures are needed for industries with high process temperatures, located in the Gulf Region, in order to minimize the enhanced risk of heat stress and illness during Ramadan.
... ted an unexpected nding about urine color, too. ey assessed the urine color of their 39 participants once before their intervention and twice a er the intervention, but found that all the assessment results were normal. There are several explanations for the discrepancy between urine color and other measures in representing elders' hydration state.Kolasa, Lackey and Grandjean (2009) asserted that the level of precision and accuracy of urine color is not the same as urine speci c gravity.Mentes, Wake eld, and Culp (2006) also insisted that urine color may not be a valid measure to evaluate hydration state of elders in long-term care facilities as those elders are su ering from diverse medical conditions that might a ...
Purpose: This study was done to evaluate the effects of a fluid intake intervention on increasing fluid intake and ameliorating dehydration status in elders admitted to long-term care hospitals. Methods: A nonequivalent control group, pretest and posttest design was used. The experimental group of 39 participants received the 4-week intervention while the control group of 38 participants received routine care. Outcome variables were daily fluid intake and physiological indexes such as blood urea nitrogen and creatinine ratio (BUN/Cr), urine specific gravity (USG), and urine color. Results: After the intervention to increase fluid intake, there were statistically significant increases in daily fluid intake, normal BUN/Cr, and USG in the experimental group. However, a statistically significant improvement in normal urine color was not found for either group. Conclusion: The findings of this study demonstrated that the fluid intake intervention improved hydration status of the experimental group participants. Consequently, it was confirmed that the intervention is considered to be effective in preventing dehydration which occurs frequently in older adults in long-term care facilities and, thus this intervention may contribute to preventing various health issues resulting from dehydration.
... 10. Stosować regularnie najprostsze metody monitorowania stanu nawodnienia organizmu [80]. ...
Water is essential for life. There wouldn't be the proper functioning of body processes without it. An inadequate water intake relative to recommendation contributes to the decline in physical capacity and adversely effects on cognitive function and mood. On the other hand, an adequate water intake helps maintain the balance between total energy intake and daily energy expenditure and determines the correct rate of fat oxidation. This might be useful and commonly used in weight reduction and thus might favorably affect on body composition in overweight and obese people by increasing the total body water and lean muscle mass and might contribute to a decrease in body fat. Research results indicate clearly that drinking water instead of caloric beverages might be an effective way to reduce daily total energy consumption and in this way might may contribute to the reduction of weight, body circumferences and body fat.
... In winter and summer, the distribution of water balance was normal; however, the range of the distribution obtained in winter was narrower than that in summer: in summer, more participants were falling in the low and high water balance categories. It may be speculated that, in hot weather conditions, water needs may be more difficult to meet when relying on thirst because, when thirst occurs, the person is already dehydrated (Kolasa et al., 2009). Also, it may be that, in response to the discomfort of hot weather, people may consume high amount of fluids, thus surpassing their water needs towards hyperhydration. ...
Water balance is achieved when water intake from solid and fluid foods and drinking water meets water losses, mainly in sweat, urine and faeces. Seasonality, particularly in Mediterranean countries that have a hot summer, may affect water loss and consequently water balance. Water balance has not been estimated before on a population level and the effect of seasonality has not been evaluated. The present study aimed to compare water balance, intake and loss in summer and winter in a sample of the general population in Greece.
The Water Balance Questionnaire (WBQ) was used to evaluate water balance, estimating water intake and loss in summer (n = 480) and in winter (n = 412) on a stratified sample of the general population in Athens, Greece.
In winter, mean (SD) water balance was −63 (1478) mL/day−1, mean (SD)water intake was 2892 (987) mL/day−1 and mean (quartile range) water loss was 2637 (1810–3922) mL/day−1. In summer, mean (SD) water balance was −58 (2150) mL/day−1, mean (SD) water intake was 3875 (1373) mL/day−1 and mean (quartile range) water loss was 3635 (2365–5258) mL/day−1. Water balance did not differ between summer and winter (P = 0.96); however, the data distribution was different; in summer, approximately 8% more participants were falling in the low and high water balance categories. Differences in water intake from different sources were identified (P < 0.05).
Water balance in summer and winter was not different. However, water intake and loss were approximately 40% higher in summer than in winter. More people were falling in the low and high water balance categories in summer when comparing the distribution on water balance in winter.
... Thirst is an unreliable indicator, as is the color of her urine, which may be affected by the medications she is taking. 12 She states she is unlikely to consume the recommended number of servings of vegetables and instead could be encouraged to find cereal and dietary supplement products with polydextrose or psyllium listed as ingredients, increasing their use gradually. Unless she changes her habit of restricting fluids, she would likely experience abdominal bloating, gas, and cramping with increased fiber intake. ...
Many Americans have chronic gastrointestinal complaints that are not medically significant. The evidence to support the efficacy of advice from health care providers, Web sites, family, and friends is limited. The efficacy of nonpharmacological approaches to preventing and/or treating chronic constipation, irritable bowel syndrome, and gastroesophageal reflux disease is presented
Purpose
Accurate data on water and beverage intakes are essential for assessing hydration adequacy and setting proper guidelines. The objective of this study is to identify the patterns and sociodemographic determinants of water intake and to assess the intake adequacy for children in China.
Methods
The study team recruited 41,439 children aged 6–17 years using a multi-stage cluster random sampling method. Daily water and beverage intakes were investigated with the standard questionnaires and measuring containers in face-to-face interviews. Each participant was assigned an adjustment weight to obtain a nationally representative sample. Sociodemographic factors influencing water intake were identified using multi-variable regressions. Water intake adequacy was evaluated by comparing with the recommended water intake (RWI).
Results
The mean ± standard deviation of total water intake (TWI) was 1603 ± 731 mL/day for boys and 1487 ± 661 mL/day for girls. Plain water, food moisture, and other beverages contributed 51%, 20%, and 29% of the TWI. Multi-variable analyses showed that TWI of children increased with age, in urban areas and day schools, and with parents’ economic and educational levels. The majority (82%) of children had TWI not meeting the corresponding RWI, and the percentage increased with age except for 14–17-year-old boys.
Conclusions
Plain water is still the major source of daily water intake by children in China. Unfortunately, the majority of children do not have sufficient water intake, which warrants future actions and guidelines targeting adequate hydration.
For nurses, shift work is a necessity, required to provide 24-h continuous care for patients. Research posits that fatigue amongst shift-working nurses is associated with inadequate and poorly timed sleep and also strongly influenced by the timing, quality and quantity of food consumed. The aim of this investigation was to examine differences and similarities in the food choices and eating patterns of nurses exposed to different lengths of time in shift work, as a means of understanding how nurses can adapt their eating patterns to better manage fatigue and sleep loss. Qualitative methodology was utilised to study and capture in-depth information about nurses’ daily working lives. A case study approach allowed for the investigation of nurses with limited and extensive experience of shift work. Increased food craving, caffeine consumption and snacking behaviours during night shifts were described by both groups of nurses, as was the inability to drink enough fluids at work. Meal skipping at work, associated with high workload, was detailed more by experienced nurses. Experienced nurses described shopping and preparing home cooked meals in advance to manage food intake and associated fatigue, contrasting with patterns from inexperienced nurses. Experienced nurses recounted drinking alcohol as a way to rest and recover from shift work, unlike their less inexperienced colleagues. These findings indicate organisational and work place issues such as shift work and rostering influence the food choices and eating patterns of shift-working nurses. Experienced nurses, however, draw on a greater range of strategies around diet and eating patterns to minimise these impacts.
Patients with type 2 diabetes mellitus are encouraged to lose weight, if overweight. At the same time, patients are often prescribed medications needed to control blood sugars but have an unwanted adverse effect contributing to weight gain. We present 2 patient cases demonstrating a multidisciplinary integrative approach to providing diabetes care while recognizing weight management concerns. The first case focuses on the kinds and amounts of information given to a patient on the day of diagnosis. The second case includes strategies to empower patients with type 2 diabetes mellitus to manage their weight and improve their glucose control through physical activity. Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Most literatures on daily water intake are focused on developed countries and to our knowledge; there is limited information on the hydration status of Nigerians. Our objective was to describe daily water intake (DWI) among Nigerian students, develop a model for the prediction of students' DWI and examine the association between DWI and four predictor variables. Data on DWI for 150 students aged 18-26 years were collected through a survey conducted at Kwara State University in February, 2013 together with information on their age, weight, gender and awareness of dieticians' recommendation. Our results indicates that students' DWI varies by gender with male students drinking more than their female counterparts; although, the awareness rate is higher in females than males. We found that nearly half of participants (44%) drank less than 2.7 L of water/day, 25% between 2.7 and 3.7 L/day and 31% reported drinking more than 3.7 L of water/day. Results also revealed that students' DWI decline with age but increases with weight and one-in-two of the students are unaware of the dangers of poor hydration. Arguably, this study is the first description of DWI among Nigerian students and fills the gap in the literature by developing two models for the prediction of students' DWI. In light of the significance of the knowledge and awareness of Dieticians' recommendation on DWI (as evidence in this study) and the low awareness rate existing among the students; nutrition and health promotion program on the benefits of adequate DWI by schools and health organizations is extremely important. This has the potential of improving the health of students.
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It is the position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine that physical activity, athletic performance, and recovery from exercise are enhanced by optimal nutrition. These organizations recommend appropriate selection of foods and fluids, timing of intake, and supplement choices for optimal health and exercise performance. This updated position paper couples a rigorous, systematic, evidence-based analysis of nutrition and performance-specific literature with current scientific data related to energy needs, assessment of body composition, strategies for weight change, nutrient and fluid needs, special nutrient needs during training and competition, the use of supplements and ergogenic aids, nutrition recommendations for vegetarian athletes, and the roles and responsibilities of sports dietitians. Energy and macronutrient needs, especially carbohydrate and protein, must be met during times of high physical activity to maintain body weight, replenish glycogen stores, and provide adequate protein to build and repair tissue. Fat intake should be sufficient to provide the essential fatty acids and fat-soluble vitamins, as well as contribute energy for weight maintenance. Although exercise performance can be affected by body weight and composition, these physical measures should not be a criterion for sports performance and daily weigh-ins are discouraged. Adequate food and fluid should be consumed before, during, and after exercise to help maintain blood glucose concentration during exercise, maximize exercise performance, and improve recovery time. Athletes should be well hydrated before exercise and drink enough fluid during and after exercise to balance fluid losses. Sports beverages containing carbohydrates and electrolytes may be consumed before, during, and after exercise to help maintain blood glucose concentration, provide fuel for muscles, and decrease risk of dehydration and hyponatremia. Vitamin and mineral supplements are not needed if adequate energy to maintain body weight is consumed from a variety of foods. However, athletes who restrict energy intake, use severe weight-loss practices, eliminate one or more food groups from their diet, or consume unbalanced diets with low micronutrient density, may require supplements. Because regulations specific to nutritional ergogenic aids are poorly enforced, they should be used with caution, and only after careful product evaluation for safety, efficacy, potency, and legality. A qualified sports dietitian and in particular in the United States, a Board Certified Specialist in Sports Dietetics, should provide individualized nutrition direction and advice subsequent to a comprehensive nutrition assessment.
It is the position of the American College of Sports Medicine that adequate fluid replacement helps maintain hydration and, therefore, promotes the health, safety, and optimal physical performance of individuals participating in regular physical activity. This position statement is based on a comprehensive review and interpretation of scientific literature concerning the influence of fluid replacement on exercise performance and the risk of thermal injury associated with dehydration and hyperthermia. Based on available evidence, the American College of Sports Medicine makes the following general recommendations on the amount and composition of fluid that should be ingested in preparation for, during, and after exercise or athletic competition: 1) It is recommended that individuals consume a nutritionally balanced diet and drink adequate fluids during the 24-hr period before an event, especially during the period that includes the meal prior to exercise, to promote proper hydration before exercise or competition. 2) It is recommended that individuals drink about 500 ml (about 17 ounces) of fluid about 2 h before exercise to promote adequate hydration and allow time for excretion of excess ingested water. 3) During exercise, athletes should start drinking early and at regular intervals in an attempt to consume fluids at a rate sufficient to replace all the water lost through sweating (i.e., body weight loss), or consume the maximal amount that can be tolerated. 4) It is recommended that ingested fluids be cooler than ambient temperature [between 15 degrees and 22 degrees C (59 degrees and 72 degrees F])] and flavored to enhance palatability and promote fluid replacement. Fluids should be readily available and served in containers that allow adequate volumes to be ingested with ease and with minimal interruption of exercise. 5) Addition of proper amounts of carbohydrates and/or electrolytes to a fluid replacement solution is recommended for exercise events of duration greater than 1 h since it does not significantly impair water delivery to the body and may enhance performance. During exercise lasting less than 1 h, there is little evidence of physiological or physical performance differences between consuming a carbohydrate-electrolyte drink and plain water. 6) During intense exercise lasting longer than 1 h, it is recommended that carbohydrates be ingested at a rate of 30-60 g.h(-1) to maintain oxidation of carbohydrates and delay fatigue. This rate of carbohydrate intake can be achieved without compromising fluid delivery by drinking 600-1200 ml.h(-1) of solutions containing 4%-8% carbohydrates (g.100 ml(-1)). The carbohydrates can be sugars (glucose or sucrose) or starch (e.g., maltodextrin). 7) Inclusion of sodium (0.5-0.7 g.1(-1) of water) in the rehydration solution ingested during exercise lasting longer than 1 h is recommended since it may be advantageous in enhancing palatability, promoting fluid retention, and possibly preventing hyponatremia in certain individuals who drink excessive quantities of fluid. There is little physiological basis for the presence of sodium in n oral rehydration solution for enhancing intestinal water absorption as long as sodium is sufficiently available from the previous meal.
To present recommendations to optimize the fluid-replacement practices of athletes.
Dehydration can compromise athletic performance and increase the risk of exertional heat injury. Athletes do not voluntarily drink sufficient water to prevent dehydration during physical activity. Drinking behavior can be modified by education, increasing accessibility, and optimizing palatability. However, excessive overdrinking should be avoided because it can also compromise physical performance and health. We provide practical recommendations regarding fluid replacement for athletes.
Educate athletes regarding the risks of dehydration and overhydration on health and physical performance. Work with individual athletes to develop fluid-replacement practices that optimize hydration status before, during, and after competition.
This Position Stand provides guidance on fluid replacement to sustain appropriate hydration of individuals performing physical activity. The goal of prehydrating is to start the activity euhydrated and with normal plasma electrolyte levels. Prehydrating with beverages, in addition to normal meals and fluid intake, should be initiated when needed at least several hours before the activity to enable fluid absorption and allow urine output to return to normal levels. The goal of drinking during exercise is to prevent excessive (>2% body weight loss from water deficit) dehydration and excessive changes in electrolyte balance to avert compromised performance. Because there is considerable variability in sweating rates and sweat electrolyte content between individuals, customized fluid replacement programs are recommended. Individual sweat rates can be estimated by measuring body weight before and after exercise. During exercise, consuming beverages containing electrolytes and carbohydrates can provide benefits over water alone under certain circumstances. After exercise, the goal is to replace any fluid electrolyte deficit. The speed with which rehydration is needed and the magnitude of fluid electrolyte deficits will determine if an aggressive replacement program is merited.
Significant scientific evidence documents the deleterious effects of hypohydration (reduced total body water) on endurance exercise performance; however, the influence of hypohydration on muscular strength, power and high-intensity endurance (maximal activities lasting >30 seconds but <2 minutes) is poorly understood due to the inconsistent results produced by previous investigations. Several subtle methodological choices that exacerbate or attenuate the apparent effects of hypohydration explain much of this variability. After accounting for these factors, hypohydration appears to consistently attenuate strength (by approximately 2%), power (by approximately 3%) and high-intensity endurance (by approximately 10%), suggesting alterations in total body water affect some aspect of force generation. Unfortunately, the relationships between performance decrement and crucial variables such as mode, degree and rate of water loss remain unclear due to a lack of suitably uninfluenced data. The physiological demands of strength, power and high-intensity endurance couple with a lack of scientific support to argue against previous hypotheses that suggest alterations in cardiovascular, metabolic and/or buffering function represent the performance-reducing mechanism of hypohydration. On the other hand, hypohydration might directly affect some component of the neuromuscular system, but this possibility awaits thorough evaluation. A critical review of the available literature suggests hypohydration limits strength, power and high-intensity endurance and, therefore, is an important factor to consider when attempting to maximise muscular performance in athletic, military and industrial settings.
When performing physical work, sweat output often exceeds water intake, producing a body water deficit or dehydration. Specific to the work place, dehydration can adversely affect worker productivity, safety, and morale. Legislative bodies in North America such as the Occupational Safety and Health Administration (OSHA) and the American Conference of Governmental Industrial Hygienists (ACGIH) recommend replacing fluids frequently when exposed to heat stress, such as one cup (250 ml) every 20 minutes when working in warm environments. However, the majority of legislative guidelines provide vague guidance and none take into account the effects of work intensity, specific environments, or protective clothing. Improved occupational guidelines for fluid and electrolyte replacement during hot weather occupational activities should be developed to include recommendations for fluid consumption before, during, and after work.
In 2004, the Institute of Medicine (IOM) issued a report presenting reference intake information about water, sodium, potassium, and other electrolytes for Americans and Canadians [11.
Institute of Medicine and Food and Nutrition Board:“Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate.”
Washington, DC: National Academies Press,2004
.View all references]. The report established, for the first time, adequate intakes (AI) for total water (from drinking water, beverages, and food) for healthy people. An AI is the recommended average daily intake level based on observed or experimentally-determined approximations or estimates of nutrient intake by a group or groups of apparently health people that are assumed to be adequate. The AI for water is based on US survey data. The recommendations about water intake are for healthy populations—they do not apply to at-risk groups.
Water supply is a basic public problem. In modern science, three periods with different approaches to define recommended water intake in adults can be distinguished. Pediatricians agree that hydration in children may be optimal only in breastfed infants. More data are required on the health effects of different hydration states and varying water intakes in particular age and gender groups to define optimal ranges of water intake. The fetus grows in an exceptionally well-hydrated environment. Water metabolism shows several peculiarities in preterm and term infants. Infant diarrhea remains a major topic of basic and clinical research. Water intoxication in infants, toddlers, and children is rare and can only be found in exceptional circumstances. Hydration status characterized by hyponatremia may play a role in the pathogenesis of febrile convulsions in toddlers. There is increasing indirect evidence that spontaneous drinking behavior of a population may be fixed and anchored in the age range of toddlers. Sex differences in hydration status are common, but not obligatory. What causes theses differences? What is behind the various circadian rhythms of urine osmolality in children? At what age and in what quantities can alcohol and caffeine consumption be tolerated? How can individual susceptibility be defined? Reflecting on the modern epidemic of obesity in children and adolescents, a public consensus concerning use and misuse of sweetened drinks seems mandatory. Dietary reference intakes of water refer to 24-hour intake. In nutritional counselling, food and meal-based dietary advice is primarily given. Young parents are confronted with a flood of advice of varying quality. Recommendations on fluid consumption should be collated and revised.
There is a rich scientific literature regarding hydration status and physical function that began in the late 1800s, although the relationship was likely apparent centuries before that. A decrease in body water from normal levels (often referred to as dehydration or hypohydration) provokes changes in cardiovascular, thermoregulatory, metabolic, and central nervous function that become increasingly greater as dehydration worsens. Similarly, performance impairment often reported with modest dehydration (e.g., -2% body mass) is also exacerbated by greater fluid loss. Dehydration during physical activity in the heat provokes greater performance decrements than similar activity in cooler conditions, a difference thought to be due, at least in part, to greater cardiovascular and thermoregulatory strain associated with heat exposure. There is little doubt that performance during prolonged, continuous exercise in the heat is impaired by levels of dehydration >or= -2% body mass, and there is some evidence that lower levels of dehydration can also impair performance even during relatively short-duration, intermittent exercise. Although additional research is needed to more fully understand low-level dehydration's effects on physical performance, one can generalize that when performance is at stake, it is better to be well-hydrated than dehydrated. This generalization holds true in the occupational, military, and sports settings.
Significant scientific evidence documents the deleterious effects of hypohydration (reduced total body water) on endurance exercise performance; however, the influence of hypohydration on muscular strength, power and high-intensity endurance (maximal activities lasting >30 seconds but <2 minutes) is poorly understood due to the inconsistent results produced by previous investigations. Several subtle methodological choices that exacerbate or attenuate the apparent effects of hypohydration explain much of this variability. After accounting for these factors, hypohydration appears to consistently attenuate strength (by ≈2%), power (by ≈3%) and high-intensity endurance (by ∼10%), suggesting alterations in total body water affect some aspect of force generation. Unfortunately, the relationships between performance decrement and crucial variables such as mode, degree and rate of water loss remain unclear due to a lack of suitably uninfluenced data. The physiological demands of strength, power and high-intensity endurance couple with a lack of scientific support to argue against previous hypotheses that suggest alterations in cardiovascular, metabolic and/or buffering function represent the performance-reducing mechanism of hypohydration. On the other hand, hypohydration might directly affect some component of the neuromuscular system, but this possibility awaits thorough evaluation. A critical review of the available literature suggests hypohydration limits strength, power and highintensity endurance and, therefore, is an important factor to consider when attempting to maximise muscular performance in athletic, military and industrial settings.
Although water is quantitatively the most import nutrient, there are no recommended dietary allowances (RDA) or adequate intake (AI) values. Based on 718 assessments of 24-hour total water intake, urine volume, and urine osmolality, individual hydration status was characterized in 479 healthy boys and girls of the DONALD study aged 4.0 to 6.9 years and 7.0 to 10.9 years. Mean 24-hour total water intake ranged from 0.90 mL/kcal to 0.96 mL/kcal, and median 24-hour urine osmolality ranged from 683 mosm/kg to 854 mosm/kg. A maximum urine osmolality of 830 mosm/kg (mean - 2 SD) in healthy children with a typical affluent Western-type diet was the physiologic criterion of the upper limit of euhydration. "Water reserve" (24-hour urine volume - hypothetical urine volume to excrete 24 urine solutes at a concentration of 830 mosm/kg) was a quantitative measure of individual 24-hour hydration status and ensuring euhydration in 97% of the subjects in each group; AI values of total water in the 4 age and sex groups ranged from 1.01 mL/kcal to 1.05 mL/kcal. These procedures to quantify 24-hour hydration status may prove valuable in investigating the effects on health of different states of euhydration.
Survival of human and animal cells requires avoidance of excessive alterations of cell volume. The osmolarity amassed by cellular accumulation of organic substances must be compensated by lowering cytosolic ion concentrations. The Na+/K+ ATPase extrudes Na+ in exchange for K+, which can permeate the cell membrane through K+ channels. K+ exit generates a cell-negative potential difference across the cell membrane, driving the exit of anions such as Cl-. The low cytosolic Cl- concentrations counterbalance the excess cellular osmolarity by organic substances. Cell volume regulation following cell swelling involves releasing ions through activation of K+ channels and/or anion channels, KCl-cotransport, or parallel activation of K+/H+ exchange and Cl-/HCO3- exchange. Cell volume regulation following cell shrinkage involves accumulation of ions through activation of Na+,K+,2Cl- cotransport, Na+/H+ exchange in parallel to Cl-/HCO3- exchange, or Na+ channels. The Na+ taken up is extruded by the Na+/K+ ATPase in exchange for K+. Shrunken cells further accumulate organic osmolytes such as sorbitol and glycerophosphorylcholine, and monomeric amino acids by altered metabolism and myoinositol (inositol), betaine, taurine, and amino acids by Na+ coupled transport. They release osmolytes during cell swelling. Challenges of cell volume homeostasis include transport, hormones, transmitters, and drugs. Moreover, alterations of cell volume participate in the machinery regulating cell proliferation and apoptotic cell death. Deranged cell volume regulation significantly contributes to the pathophysiology of several disorders such as liver insufficiency, diabetic ketoacidosis, hypercatabolism, fibrosing disease, sickle cell anemia, and infection.
The performance of both physical and mental tasks can be adversely affected by heat and by dehydration. There are well-recognized effects of heat and hydration status on the cardiovascular and thermoregulatory systems that can account for the decreased performance and increased sensation of effort that are experienced in the heat. Provision of fluids of appropriate composition in appropriate amounts can prevent dehydration and can greatly reduce the adverse effects of heat stress. There is growing evidence that the effects of high ambient temperature and dehydration on exercise performance may be mediated by effects on the central nervous system. This seems to involve serotonergic and dopaminergic functions. Recent evidence suggests that the integrity of the blood brain barrier may be compromised by combined heat stress and dehydration, and this may play a role in limiting performance in the heat.
Various reports indicate that humans receive 20-25% of their daily water intake from food. Fruits, vegetables and other high-moisture foods, therefore, make an important contribution to total fluid intake. In addition, co-ingestion of other nutrients and ingredients can impact drinking behavior, absorption, distribution and retention of water, all of which contribute to the person's hydration state. Therefore, a food's hydration value derives from the interaction between its water content and the presence of these co-nutrients and ingredients. Research is reviewed in this paper showing increased voluntary fluid intake of young boys during exercise when the beverage is flavored and contains sodium chloride and carbohydrate. Additional research on rehydration after exercise and heat exposure showed improved recovery of plasma volume and fluid status when food was ingested before consuming water in the two hours after exercise. Collectively, these findings point to an interaction between fluid intake and co-ingested nutrients in regulating human hydration during and after exercise.
The Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate, provided extensive tables of data on total water intake, water intake from beverages and water intake from foods; however, very little information was provided about the specific details of these analyses. Reported total water intake varied with gender and somewhat with age and suggested that further sources of variation in total water intake were due to differences in body size, physical activity, and climatic exposure.
In an attempt to better understand the variation in reported water intake, we examined water intake from foods and beverages and plain water intake in the National Health and Nutrition Examination Surveys (NHANES), 1999-2002.
Non-Hispanic black children (4 to 18 years) had less water from food and beverages (approximately 0.15 L/day) than non-Hispanic whites and Hispanics. Non-Hispanic black children had less (approximately 0.15 L/day) plain water than other ethnicities. Adult non-Hispanic whites had more water intake from food and beverages (approximately 0.4 L/day) and non-Hispanic blacks had less (approximately 0.2 L/day) than Hispanics and Other ethnic group. Non-Hispanic black adults had less (approximately 0.2 L/day) plain water than non-Hispanic whites and the Other ethnic group but had similar plain water consumption as Hispanics.
These data indicate further investigation into the sources of variation of water intake should include consideration of ethnic differences.
Acknowledging that total body water (TBW) turnover is complex, and that no measurement is valid for all situations, this review evaluates 13 hydration assessment techniques. Although validated laboratory methods exist for TBW and extracellular volume, no evidence incontrovertibly demonstrates that any concentration measurement, including plasma osmolality (P(osm)), accurately represents TBW gain and loss during daily activities. Further, one blood or urine sample cannot validly represent fluctuating TBW and fluid compartments. Future research should (a) evaluate novel techniques that assess hydration in real time and are precise, accurate, reliable, non-invasive, portable, inexpensive, safe, and simple; and (b) clarify the relationship between P(osm) and TBW oscillations in various scenarios.
Primary care providers (PCPs) are increasing their use of evidence-based medicine (EBM) in the care they give patients. They evaluate the available evidence to determine if it applies to their patients and seek to complement their clinical experience with EBM to improve patient outcomes. In evidence-based practices, patient oriented data are valued more highly than disease oriented evidence. More than 8 million biomedical articles are published annually, but only an estimated 2% of those are relevant to improved patient outcomes (POEMs - patient oriented evidence that matters). This paper describes some of the tools used by PCPs to search for evidence and the decision-making process used to determine if they will change their practice. Understanding how PCPs evaluate research findings and other evidence can help hydration researchers frame their research questions and study reports.
The limited literature on the effects of dehydration on human cognitive function is contradictory and inconsistent. Although it has been suggested that decrements in cognitive performance are present in the range of a 2 to 3% reduction in body weight, several dose-response studies indicate dehydration levels of 1% may adversely affect cognitive performance. When a 2% or more reduction in body weight is induced by heat and exercise exposure, decrements in visual-motor tracking, short-term memory and attention are reported, but not all studies find behavioral effects in this range. Future research should be conducted using dose-response designs and state-of-the-art behavioral methods to determine the lowest levels of dehydration that produce substantive effects on cognitive performance and mood. Confounding factors, such as caffeine intake and the methods used to produce dehydration, need to be considered in the design and conduct of such studies. Inclusion of a positive control condition, such as alcohol intake, a hypnotic drug, or other treatments known to produce adverse changes in cognitive performance should be included in such studies. To the extent possible, efforts to blind both volunteers and investigators should be an important consideration in study design.
Human neuropsychology investigates brain-behavior relationships, using objective tools (neurological tests) to tie the biological and behavior aspects together. The use of neuropsychological assessment tools in assessing potential effects of dehydration is a natural progression of the scientific pursuit to understand the physical and mental ramifications of dehydration. It has long been known that dehydration negatively affects physical performance. Examining the effects of hydration status on cognitive function is a relatively new area of research, resulting in part from our increased understanding of hydration's impact on physical performance and advances in the discipline of cognitive neuropsychology. The available research in this area, albeit sparse, indicates that decrements in physical, visuomotor, psychomotor, and cognitive performance can occur when 2% or more of body weight is lost due to water restriction, heat, and/or physical exertion. Additional research is needed, especially studies designed to reduce, if not remove, the limitations of studies conducted to date.
Many diseases have multifactorial origins. There is increasing evidence that mild dehydration plays a role in the development of various morbidities. In this review, effects of hydration status on acute and chronic diseases are depicted (excluding the acute effects of mild dehydration on exercise performance, wellness, cognitive function, and mental performance) and categorized according to four categories of evidence (I-IV). Avoidance of a high fluid intake as a precautionary measure may be indicated in patients with cardiovascular disorders, pronounced chronic renal failure (III), hypoalbuminemia, endocrinopathies, or in tumor patients with cisplatin therapy (IIb) and menace of water intoxication. Acute systemic mild hypohydration or dehydration may be a pathogenic factor in oligohydramnios (IIa), prolonged labor (IIa), cystic fibrosis (III), hypertonic dehydration (III), and renal toxicity of xenobiotica (Ib). Maintaining good hydration status has been shown to positively affect urolithiasis (Ib) and may be beneficial in treating urinary tract infection (IIb), constipation (III), hypertension (III), venous thromboembolism (III), fatal coronary heart disease (III), stroke (III), dental disease (IV), hyperosmolar hyperglycemic diabetic ketoacidosis (IIb), gallstone disease (III), mitral valve prolapse (IIb), and glaucoma (III). Local mild hypohydration or dehydration may play a critical role in the pathogenesis of several broncho-pulmonary disorders like exercise asthma (IIb) or cystic fibrosis (Ib). In bladder and colon cancers, the evidence on hydration status' effects is inconsistent.
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