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Total water intake is seldom reported in dietary surveys and hydration status is rarely measured. Although adequate intake (AI) levels have been suggested by the European Food Safety Authority, the World Health Organization and the Institute of Medicine, uncertainties and confused messages abound regarding optimum intake. This paper reviews data on water intake internationally and examines associations with beverage consumption habits of adults in the UK, as determined from secondary analysis of individual diet records. On average, total water intake among British adults was equivalent to the European AI (2 l/day for women, 2.5 l/day for men) and 75% of this was derived from beverages. Factors that correlated with high total water intake included the consumption of a variety of beverages and drinking in the evening. Total water intake (and the contribution from soft drinks) is markedly higher in the USA than in Europe. Beverage consumption habits and trends were also reviewed. In the past 10 years, water beverages have become more popular and as such the overall energy contribution from beverages has declined slightly. Most people could be encouraged to drink a variety of beverages to maintain adequate hydration and to balance the energy content according to their needs. However, further work is needed to refine recommendations for water intake, as basing these on observational epidemiological data is essentially a circular argument. A standardized measurement tool, validated against biomarkers of hydration status, would be a step forward in assessing the adequacy of water intakes at a population level. Research may also be warranted to explore the context of drinking occasions (including time of day, weekdays weekends, lifestyle and meal patterns) as these may have an impact on water intake, hydration and also energy balance. [ABSTRACT FROM AUTHOR]

In addition to its renal and cardiovascular functions, angiotensin signalling is thought to be responsible for the increases in salt and water intake caused by hypovolaemia. However, it remains unclear whether these behaviours require angiotensin production in the brain or liver. Here, we use in situ hybridization to identify tissue‐specific expression of the genes required for producing angiotensin peptides, and then use conditional genetic deletion of the angiotensinogen gene (Agt) to test whether production in the brain or liver is necessary for sodium appetite and thirst. In the mouse brain, we identified expression of Agt (the precursor for all angiotensin peptides) in a large subset of astrocytes. We also identified Ren1 and Ace (encoding enzymes required to produce angiotensin II) expression in the choroid plexus, and Ren1 expression in neurons within the nucleus ambiguus compact formation. In the liver, we confirmed that Agt is widely expressed in hepatocytes. We next tested whether thirst and sodium appetite require angiotensinogen production in astrocytes or hepatocytes. Despite virtually eliminating expression in the brain, deleting astrocytic Agt did not reduce thirst or sodium appetite. Despite markedly reducing angiotensinogen in the blood, eliminating Agt from hepatocytes did not reduce thirst or sodium appetite, and in fact, these mice consumed the largest amounts of salt and water after sodium deprivation. Deleting Agt from both astrocytes and hepatocytes also did not prevent thirst or sodium appetite. Our findings suggest that angiotensin signalling is not required for sodium appetite or thirst and highlight the need to identify alternative signalling mechanisms. Key points: Angiotensin signalling is thought to be responsible for the increased thirst and sodium appetite caused by hypovolaemia, producing elevated water and sodium intake.Specific cells in separate brain regions express the three genes needed to produce angiotensin peptides, but brain‐specific deletion of the angiotensinogen gene (Agt), which encodes the lone precursor for all angiotensin peptides, did not reduce thirst or sodium appetite.Double‐deletion of Agt from brain and liver also did not reduce thirst or sodium appetite.Liver‐specific deletion of Agt reduced circulating angiotensinogen levels without reducing thirst or sodium appetite. Instead, these angiotensin‐deficient mice exhibited an enhanced sodium appetite.Because the physiological mechanisms controlling thirst and sodium appetite continued functioning without angiotensin production in the brain and liver, understanding these mechanisms requires a renewed search for the hypovolaemic signals necessary for activating each behaviour. [ABSTRACT FROM AUTHOR]

Aim: Water is critical for human survival, yet water intake equations may not reflect contemporary populations. This research aims to determine the total water intake of a representative Australian population, per kilogram of body weight (mL/kg) and stratified by age and sex. Methods: A secondary analysis of the 2011 to 2013 National Nutrition and Physical Activity Survey (n = 10 146) was conducted. Dietary intake from food and beverages was assessed by a 24‐hour recall, with respondent's weight objectively measured. Data were descriptively analysed, with multiple linear regressions used to identify the impact of demographic and physiologic factors on total water intake (mL/kg). Results: The median (interquartile range) daily total water intake per kilogram of body weight for children (2‐8 years), adolescents (9‐18 years) and adults (19+ years) were 77.1 (57.4‐100) mL/kg, 40.4 (29.3‐53.4) mL/kg and 35.5 mL/kg (26.1‐47.8), respectively. Increasing height and waist circumference were associated with reduced total water intake, with a change of −1.03 mL/kg (−1.43, −0.618) [coefficient (95% confidence interval)] in children for height and −0.448 mL/kg (−0.484, −0.412) in adults for waist circumference. Similarly, seasonality decreased intake, with greatest reductions in winter [adolescents: −4.11 mL/kg (−6.83, −1.40)]. In comparison, being male, living in rural areas and having a physical occupation were associated with greater intake, by 1.73 mL/kg (0.347, 3.10), 4.74 mL/kg (3.47, 6.00) and 2.82 (trade workers: 1.08, 4.59) in adults, respectively. Conclusions: Total water intake (mL/kg) decreased with age in both sexes. The results highlight possibilities to incorporate other factors into water intake equations to improve their accuracy. [ABSTRACT FROM AUTHOR]

Background 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. Methods 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. Results 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). Conclusions 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. [ABSTRACT FROM AUTHOR]

Lesions of the tuberomammillary complex, a neuroanatomical system closely related to the hypothalamic supraoptic and paraventricular nuclei, induce strong polydipsia in male rats. It was recently demonstrated that this increase in water intake is immediate, persistent, follows circadian rhythms and appears to be related to sodium regulation. The present study found that urine osmolality was significantly lower in tuberomammillary-lesioned animals vs. their respective controls at 8:00 h after surgery. Therefore, the aim of the present study was to examine the natriuretic effect of intraperitoneal oxytocin (OT) administration on medial ventral tuberomammillary nucleus (E3) polydipsia and polyuria of lesioned and control male rats. At 24:00 h post-lesion, OT blocked the hyperdipsic and polyuric responses of E3-lesioned animals but not those of non-lesioned controls, which did however significantly increase their water intake. Moreover, urinary osmolality and sodium excretion increased in E3 -lesioned animals that received OT but not in lesioned controls receiving physiological saline (992 ± 187.19 vs. 215.83 ± 23.39 mOsm/kg; 1.68 ± 0.13 vs. 0.47 ± 0.1 mEq/L). At 48:00 h post-lesion, OT administration also induced a higher intake of water and of simultaneously offered hypertonic NaCl (1.5%) in E3-lesioned animals. These results are interpreted in terms of the hypothalamic systems involved in sodium and water homeostasis. [ABSTRACT FROM AUTHOR]

The effects of the 5-HT1A receptor agonist 8-OH-DPAT on food and water intake in male broiler chickens were investigated. The injection of 25 or 50 μg/kg of 8-OH-DPAT 15 min before refeeding in fasted animals produced a decrease in food intake. No effect was observed in drinking. The injection of 25 or 50 μg/kg of the 8-OH-DPAT 60 min after the start of refeeding did not produce any significant modification in food intake. No effect on drinking was recorded. The agonist 8-OH-DPAT injected 15 min before water presentation in water-deprived chickens, produced an increased drinking 60 min after the presentation of water. No effect on food intake was observed. The results show that the effect on food intake of the agonist 8-OH-DPAT in fasted–refed broiler chickens was similar to those observed in mammals and layer-strain chickens. However, the agonist did not alter significantly the food intake when the broilers were fed 60 min before the injection. These results are contrary to the observed effects in mammals and in layer-strain chickens. Probably, the selection for rapid growth rate in broilers causes modifications in the feeding control pattern. The comparison between broilers and layers strain may be a useful tool to elucidate the complex mechanisms involved in food and water intake regulation in chickens. [ABSTRACT FROM AUTHOR]

Water drinking habits during flight in adult mayflies of Epeorus ikanonis Takahashi were observed and the effect of water intake on their longevity was examined. The study was carried out in a mountain stream in western Japan. Adult males collected a water droplet under the head capsule while alighting on the water surface and consumed it after moving to nearby riparian vegetation. The amount of water intake was experimentally estimated to be 9.7% of the bodyweight for males. Although females did not show the water drinking behavior in the field, they imbibed as much as 5.5% of the bodyweight of water in an experimental situation. Morphological observation of the mouthparts revealed that the water was drawn in through the pits at the base of the labrum. In the field caging experiment, males with a water supply had a substantially longer life span than those without. Increase in adult life span by drinking water was less marked in females. Multiple copulation was observed in both sexes during the experiment. The water drinking behavior of the males may closely relate to mating success through increased longevity. Variation in the longevity of adult mayflies was discussed with regard to the possibility of water intake. [ABSTRACT FROM AUTHOR]

In the clinical setting, acute injuries in hypothalamic mediobasal regions, along with polydipsia and polyuria, have been observed in patients with cerebral salt wasting (CSW). CSW is also characterised by hypovolaemia and hyponatraemia as a result of an early increase in natriuretic peptide activity. Salt and additional amounts of fluid are the main treatment for this disorder. Similarly, experimental lesions to these brain regions, which include the median eminence (ME), produce a well‐documented neurological model of polydipsia and polyuria in rats, which is preceded by an early sodium excretion of unknown cause. In the present study, oxytocin (OT) was used to increase the renal sodium loss and prolong the hydroelectrolyte abnormalities of ME‐lesioned animals during the first few hours post‐surgery. The objective was to determine whether OT‐treated ME‐lesioned animals increase their sodium appetite and water intake to restore the volume and composition of extracellular body fluid. Electrolytic lesion of the ME increased water intake, urinary volume and sodium excretion of food‐deprived rats and also decreased urine osmolality and estimated plasma sodium concentration. OT administration at 8 hours post‐surgery reduced water intake, urine output and plasma sodium concentration and also increased urine osmolality and urine sodium excretion between 8 and 24 hours post‐lesion. From 24 to 30 hours, more water and hypertonic NaCl was consumed by OT‐treated ME‐lesioned rats than by physiological saline‐treated‐ME‐lesioned animals. Food availability from 30 to 48 hours reduced the intake of hypertonic saline solution by ME/OT animals, which increased their water and food intake during this period. OT administration therefore appears to enhance the natriuretic effect of ME lesion, producing hydroelectrolyte changes that reduce the water intake of food‐deprived animals. Conversely, the presence of hypertonic NaCl increases the fluid intake of these animals, possibly as a result of the plasma sodium depletion and hypovolaemic states previously generated. Finally, the subsequent increase in food intake by ME/OT animals reduces their need for hypertonic NaCl but not water, possibly in response to osmotic thirst. These results are discussed in relation to a possible transient activation of the ME with the consequent secretion of natriuretic peptides stored in terminal swellings, which would be augmented by OT administration. Electrolytic lesion of the ME may therefore represent a useful neurobiological model of CSW. [ABSTRACT FROM AUTHOR]