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Effects of Exercise on Acute Kidney Injury Biomarkers and the Potential Influence of Fluid Intake.
Juett, LA, James, LJ, Mears, SA
Annals of nutrition & metabolism. 2020;:53-59
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Abstract
Acute kidney injury (AKI) incidence (diagnosed by changes in serum creatinine [Cr]) following prolonged endurance events has been reported to be anywhere from 4 to 85%, and hypohydration may contribute to this. Whilst an increase in serum Cr indicates impaired kidney function, this might be influenced by muscle damage. Therefore, the use of other AKI biomarkers which can detect renal tubular injury may be more appropriate. The long-term consequences of AKI are not well understood, but there are some potential concerns of an increased subsequent risk of chronic kidney disease (CKD). Therefore, this brief review explores the effects of exercise training/competition on novel AKI biomarkers and the potential influence of fluid intake. The increase in novel AKI biomarkers following prolonged endurance events suggests renal tubular injury. This is likely due to the long duration and relatively high exercise intensity, producing increased sympathetic tone, body temperature, hypohydration, and muscle damage. Whilst muscle damage appears to be an important factor in the pathophysiology of exercise-associated AKI, it may require coexisting hypohydration. Fluid intake seems to play a role in exercise-associated AKI, as maintaining euhydration with water ingestion during simulated physical work in the heat appears to attenuate rises in AKI biomarkers. The composition of fluid intake may also be important, as high-fructose drinks have been shown to exacerbate AKI biomarkers. However, it is yet to be seen if these findings are applicable to athletes performing strenuous exercise in a temperate environment. Additionally, further work should examine the effects of repeated bouts of strenuous exercise on novel AKI biomarkers.
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Fluid Intake Recommendation Considering the Physiological Adaptations of Adults Over 65 Years: A Critical Review.
Masot, O, Miranda, J, Santamaría, AL, Paraiso Pueyo, E, Pascual, A, Botigué, T
Nutrients. 2020;(11)
Abstract
The aim of this critical review was to clarify recommended fluid intake for older people. A literature search of published articles and guidelines on fluid intake recommendations until April 2020 was carried out using PUBMED, Scopus, Cochrane, and Google Scholar. In this review, we focused on people over 65 years old at different care levels. The results show that the mean fluid intake ranges between 311 and 2390 mL/day. However, it is difficult to know whether this corresponds to the real pattern of fluid intake, due to the variability of data collection methods. With respect to the recommendations, most international organizations do not take into consideration the physiology of ageing or the health problems associated with an older population. In conclusions, we recommend to follow the guideline of the European Society for Clinical Nutrition and Metabolism (ESPEN) and the European Food Safety Authority (EFSA). ESPEN is the only guideline which takes into account age. It is also based on EFSA recommendations. This authority takes into consideration all fluids consumed (ranging from food to fluids). If it is known that around 20% of all fluids consumed come from food, the result would effectively be that the EFSA recommends the same as the ESPEN guidelines: 1.6 L/day for females and 2.0 L/day for males. The findings could help raise the awareness of professionals in the sector with respect to the required fluid intake of the elderly and, in this way, contribute to avoiding the consequences of dehydration.
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Distinguishing Low and High Water Consumers-A Paradigm of Disease Risk.
Armstrong, LE, Muñoz, CX, Armstrong, EM
Nutrients. 2020;(3)
Abstract
A long-standing body of clinical observations associates low 24-h total water intake (TWI = water + beverages + food moisture) with acute renal disorders such as kidney stones and urinary tract infections. These findings prompted observational studies and experimental interventions comparing habitual low volume (LOW) and high volume (HIGH) drinkers. Investigators have learned that the TWI of LOW and HIGH differ by 1-2 L·d-1, their hematological values (e.g., plasma osmolality, plasma sodium) are similar and lie within the laboratory reference ranges of healthy adults and both groups appear to successfully maintain water-electrolyte homeostasis. However, LOW differs from HIGH in urinary biomarkers (e.g., reduced urine volume and increased osmolality or specific gravity), as well as higher plasma concentrations of arginine vasopressin (AVP) and cortisol. Further, evidence suggests that both a low daily TWI and/or elevated plasma AVP influence the development and progression of metabolic syndrome, diabetes, obesity, chronic kidney disease, hypertension and cardiovascular disease. Based on these studies, we propose a theory of increased disease risk in LOW that involves chronic release of fluid-electrolyte (i.e., AVP) and stress (i.e., cortisol) hormones. This narrative review describes small but important differences between LOW and HIGH, advises future investigations and provides practical dietary recommendations for LOW that are intended to decrease their risk of chronic diseases.
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A Journey through the Early Evidence Linking Hydration to Metabolic Health.
Vanhaecke, T, Perrier, ET, Melander, O
Annals of nutrition & metabolism. 2020;:4-9
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Abstract
The idea that water intake or hydration may play an intrinsic, independent role in modulating metabolic disease risk is relatively recent. Here, we outline the journey from early experimental works to more recent evidence linking water and hydration to metabolic health. It has been known for decades that individuals with existing metabolic dysfunction experience challenges to body water balance and have elevated arginine vasopressin (AVP), a key hormone regulating body fluid homeostasis. Later, intervention studies demonstrated that altering fluid balance in these individuals could worsen their condition, suggesting that hydration played a role in modulating glycemic control. More recently, observational and interventional studies in healthy individuals have implicated the hydration-vasopressin axis in the pathophysiology of metabolic diseases. Individuals with higher AVP (or its surrogate, copeptin) are at higher risk for developing type 2 diabetes and components of the metabolic syndrome, an association that remains even when controlling for known risk factors. Supporting preclinical work also suggests a causal role for AVP in metabolic dysfunction. It is known that individuals who habitually drink less fluids tend to have higher circulating AVP, which may be lowered by increasing water intake. In the short term, water supplementation in habitual low drinkers with high copeptin may reduce fasting glucose or glucagon, generating a proof of concept for the role of water supplementation in reducing incident metabolic disease. A large randomized trial is ongoing to determine whether water supplementation for 1 year in subjects with low water intake can meaningfully reduce fasting glucose, risk of new-onset diabetes, and other cardiometabolic risk factors.
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[How to improve hydration and fluid intake in institutionalized older people? A scientific literature review].
Masot, O, Iglesias Millán, A, Nuin, C, Miranda, J, Lavedán, A, Botigué, T
Nutricion hospitalaria. 2018;(6):1441-1449
Abstract
BACKGROUND residents are vulnerable to suffer of dehydration due to physiological changes and the physical and cognitive limitations. AIM: to handle this situation, it has been decided to evaluate the interventions which are carried out for the management of dehydration and low fluid intake in older people living in nursing homes. METHODS the revised scientific literature review methodology of PRISMA was applied. An electronic database search was performed in PubMed, Scopus, CINAHL and other sources databases. The literature search was carried out between October 2016 and January 2017. Out of a total of 3,379 articles extracted, eleven studies were selected for analysis. In addition, their quality was assessed through Cochrane and the Newcastle-Ottawa Scale. RESULTS the risk of bias in the studies was mostly medium. Regarding the results, the interventions were classified according to whether they were invasive or non-invasive. Invasive interventions were intravenous and/or subcutaneous fluid therapy. Their effectiveness was related to the clinical improvement of dehydration. However, local reactions appeared. Non-invasive interventions focused on the individualized assistance, the stimulation to drink more and the consideration of the preferences of each resident, producing an increase in fluid intake and an improvement in analytical parameters. CONCLUSIONS given the peculiarities of the institutionalized elderly population, both types of intervention have been shown to have a positive effect on improving hydration. Nonetheless, non-invasive interventions have confirmed to be more efficient given their simplicity of application and cause fewer adverse effects.
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Under What Conditions do Water-Intervention Studies Significantly Improve Child Body Weight?
Stookey, JD
Annals of nutrition & metabolism. 2017;:62-67
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Abstract
There are particular conditions that may optimize the effects of drinking-water interventions on body weight change and risk of obesity. Strategic planning to create and sustain conditions for optimal effects of drinking water may maximize the impact of school-based interventions to reduce childhood obesity. This paper proposes questions about the target population, type of diet and activity level that will be maintained during the intervention, and planned intervention message(s). The proposed questions are motivated by conditions associated with significant effects of drinking water in randomized controlled trials. They are discussed in relation to conditions underlying the recently successful school-based drinking-water intervention in New York City. If conditions allow, school-based drinking-water interventions have the potential to efficiently benefit millions of children worldwide, who are at risk of becoming obese.
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Shifting Focus: From Hydration for Performance to Hydration for Health.
Perrier, ET
Annals of nutrition & metabolism. 2017;:4-12
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Abstract
Over the past 10 years, literature on hydration biomarkers has evolved considerably - from (de)hydration assessment towards a more global definition of biomarkers of hydration in daily life. This shift in thinking about hydration markers was largely driven by investigating the differences that existed between otherwise healthy individuals whose habitual, ad-libitum drinking habits differ, and by identifying physiological changes in low-volume drinkers who subsequently increase their water intake. Aside from obvious differences in urinary volume and concentration, a growing body of evidence is emerging that links differences in fluid intake with small, but biologically significant, differences in vasopressin (copeptin), glomerular filtration rate, and markers of metabolic dysfunction or disease. Taken together, these pieces of the puzzle begin to form a picture of how much water intake should be considered adequate for health, and represent a shifting focus from hydration for performance, toward hydration for health outcomes. This narrative review outlines the key areas of research in which the global hydration process - including water intake, urinary hydration markers, and vasopressin - has been associated with health outcomes, focusing on kidney and metabolic endpoints. It will also provide a commentary on how various hydration biomarkers may be used in hydration for health assessment. Finally, if adequate water intake can play a role in maintaining health, how might we tell if we are drinking enough? Urine output is easily measured, and can take into account differences in daily physical activity, climate, dietary solute load, and other factors that influence daily water needs. Today, targets have been proposed for urine osmolality, specific gravity, and color that may be used by researchers, clinicians, and individuals as simple indicators of optimal hydration. However, there remain a large number of incomplete or unanswered research questions regarding the relationships between water intake, hydration, vasopressin, and health outcomes. Thus, this emerging field represents an excellent opportunity, particularly for young researchers, to develop relevant and novel lines of research.
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Relationship between Sodium Intake and Water Intake: The False and the True.
Bankir, L, Perucca, J, Norsk, P, Bouby, N, Damgaard, M
Annals of nutrition & metabolism. 2017;:51-61
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Abstract
Generally, eating salty food items increases thirst. Thirst is also stimulated by the experimental infusion of hypertonic saline. But, in steady state, does the kidney need a higher amount of water to excrete sodium on a high than on a low sodium intake? This issue is still controversial. The purpose of this review is to provide examples of how the kidney handles water in relation to salt intake/output. It is based on re-analysis of previously published studies in which salt intake was adjusted to several different levels in the same subjects, and in databases of epidemiologic studies in populations on an ad libitum diet. Summary and Key Messages: These re-analyses allow us to draw the following conclusions: (1) In a steady state situation, the urine volume (and thus the fluid intake) remains unchanged over a large range of sodium intakes. The adaptation to a higher sodium excretion rests only on changes in urinary sodium concentration. However, above a certain limit, this concentration cannot increase further and the urine volume may then increase. (2) In population studies, it is not legitimate to assume that sodium is responsible for changes in urine volume, since people who eat more sodium also eat more of other nutrients leading to an increase in the excretion of potassium, urea and other solutes, besides sodium. (3) After an abrupt increase in sodium intake, fluid intake is increased in the first few days, but urine volume does not change. The extra fluid drunk is responsible for an increase in body weight.
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Effects of Dehydration on Brain Functioning: A Life-Span Perspective.
Pross, N
Annals of nutrition & metabolism. 2017;:30-36
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Abstract
BACKGROUND In the last 10 years, there has been an increase in the publication of literature dealing with the effects of mild dehydration on cognition in healthy adults. Fewer studies, leading to less consistent data, involved other age groups. SUMMARY In healthy young adults refraining from drinking or participating in dehydration protocols, it was found that mild dehydration had no impact on performance, whereas the mood was widely impaired. Several studies have also been conducted in young children either as observational studies or as interventional studies. Nevertheless, methodological differences in (de)hydration monitoring, in cognitive assessments, and in the age/brain maturation of study participants, often resulted in contradictory findings regarding the cognitive functions impacted by (de)hydration. Although not consistent, these data showed that not only mood but also performance tend to be impaired by dehydration in children. Even if older adults are likely to be more vulnerable to dehydration than younger adults, very few studies have been conducted in this regard in this population. The results show that, like it is in children, cognition tends to be impaired when the elderly are dehydrated. Taken together, these studies suggest that dehydration has greater detrimental effects in vulnerable populations. Recent imaging data suggest that the brain of children and elderly adults may have fewer resources to manage the effects of dehydration. Consequently, cognitive tasks may be more demanding for younger and older brains and performance more likely to be impaired in these populations, in comparison to young healthy subjects who have greater and more efficient resources.
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Negative, Null and Beneficial Effects of Drinking Water on Energy Intake, Energy Expenditure, Fat Oxidation and Weight Change in Randomized Trials: A Qualitative Review.
Stookey, JJ
Nutrients. 2016;(1)
Abstract
Drinking water has heterogeneous effects on energy intake (EI), energy expenditure (EE), fat oxidation (FO) and weight change in randomized controlled trials (RCTs) involving adults and/or children. The aim of this qualitative review of RCTs was to identify conditions associated with negative, null and beneficial effects of drinking water on EI, EE, FO and weight, to generate hypotheses about ways to optimize drinking water interventions for weight management. RCT conditions that are associated with negative or null effects of drinking water on EI, EE and/or FO in the short term are associated with negative or null effects on weight over the longer term. RCT conditions that are associated with lower EI, increased EE and/or increased FO in the short term are associated with less weight gain or greater weight loss over time. Drinking water instead of caloric beverages decreases EI when food intake is ad libitum. Drinking water increases EE in metabolically-inflexible, obese individuals. Drinking water increases FO when blood carbohydrate and/or insulin concentrations are not elevated and when it is consumed instead of caloric beverages or in volumes that alter hydration status. Further research is needed to confirm the observed associations and to determine if/what specific conditions optimize drinking water interventions for weight management.