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Effects of a 14-Day Hydration Intervention on Individuals with Habitually Low Fluid Intake.
Caldwell, AR, Rosa-Caldwell, ME, Keeter, C, Johnson, EC, Péronnet, F, Ganio, MS
Annals of nutrition & metabolism. 2020;:67-68
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Abstract
BACKGROUND Debate continues over whether or not individuals with low total water intake (TWI) are in a chronic fluid deficit (i.e., low total body water) [1]. When women with habitually low TWI (1.6 ± 0.5 L/day) increased their fluid intake (3.5 ± 0.1 L/day) for 4 days 24-h urine osmolality decreased, but there was no change in body weight, a proxy for total body water (TBW) [2]. In a small (n = 5) study of adult men, there were no observable changes in TBW, as measured by bioelectrical impedance, after increasing TWI for 4 weeks [3]. However, body weight increased and salivary osmolality decreased indicating that the study may have been underpowered to detect changes in TBW. Further, no studies to date have measured changes in blood volume (BV) when TWI is increased. OBJECTIVES Therefore, the purpose of this study was to identify individuals with habitually low fluid intake and determine if increasing TWI, for 14 days, resulted in changes in TBW or BV. METHODS In order to identify individuals with low TWI, 889 healthy adults were screened. Participants with a self-reported TWI less than 1.8 L/day (men) or 1.2 L/day (women), and a 24-h urine osmolality greater than 800 mOsm were included in the intervention phase of the study. For the intervention phase, 15 participants were assigned to the experimental group and 8 participants were assigned to the control group. The intervention period lasted for 14 days and consisted of 2 visits to our laboratory: one before the intervention (baseline) and 14 days into the intervention (14-day follow-up). At these visits, BV was measured using a CO-rebreathe procedure and deuterium oxide (D2O) was administered to measure TBW. Urine samples were collected immediately prior, and 3-8 h after the D2O dose to allow for equilibration. Prior to each visit, participants collected 24-h urine to measure 24-h hydration status. After the baseline visit, the experimental group increased their TWI to 3.7 L for males and 2.7 L for females in order to meet the current Institute of Medicine recommendations for TWI. RESULTS Twenty-four-hour urine osmolality decreased (-438.7 ± 362.1 mOsm; p < 0.001) and urine volume increased (1,526 ± 869 mL; p < 0.001) in the experimental group from baseline, while there were no differences in osmolality (-74.7 ± 572 mOsm; p = 0.45), or urine volume (-32 ± 1,376 mL; p = 0.89) in the control group. However, there were no changes in BV (Fig. 1a) or changes in TBW (Fig. 1b) in either group. CONCLUSIONS Increasing fluid intake in individuals with habitually low TWI increases 24-h urine volume and decreases urine osmolality but does not result in changes in TBW or BV. These findings are in agreement with previous work indicating that TWI interventions lasting 3 days [2] to 4 weeks [3] do not result in changes in TBW. Current evidence would suggest that the benefits of increasing TWI are not related changes in TBW.
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Water Supplementation Reduces Copeptin and Plasma Glucose in Adults With High Copeptin: The H2O Metabolism Pilot Study.
Enhörning, S, Brunkwall, L, Tasevska, I, Ericson, U, Persson Tholin, J, Persson, M, Lemetais, G, Vanhaecke, T, Dolci, A, Perrier, ET, et al
The Journal of clinical endocrinology and metabolism. 2019;(6):1917-1925
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Abstract
OBJECTIVE Because elevated copeptin, a marker of vasopressin, is linked to low water intake and high diabetes risk, we tested the effect of water supplementation on copeptin and fasting glucose. DESIGN, SETTING, AND PARTICIPANTS Thirty-one healthy adults with high copeptin (>10.7 pmol · L-1 in men and >6.1 pmol·L-1 in women) identified in a population-based survey from 2013 to 2015 and with a current 24-hour urine osmolality of >600 mOsm · kg-1 were included. INTERVENTION Addition of 1.5 L water daily on top of habitual fluid intake for 6 weeks. MAIN OUTCOME MEASURE Pre- and postintervention fasting plasma copeptin concentrations. RESULTS Reported mean water intake increased from 0.43 to 1.35 L · d-1 (P < 0.001), with no other observed changes in diet. Median (interquartile range) urine osmolality was reduced from 879 (705, 996) to 384 (319, 502) mOsm · kg-1 (P < 0.001); urine volume increased from 1.06 (0.90, 1.20) to 2.27 (1.52, 2.67) L · d-1 (P < 0.001); and baseline copeptin decreased from 12.9 (7.4, 21.9) pmol · L-1 to 7.8 (4.6;11.3) pmol · L-1 (P < 0.001). Water supplementation reduced fasting plasma glucose from a mean (SD) of 5.94 (0.44) to 5.74 (0.51) (P = 0.04). The water-associated reduction of both fasting copeptin and glucose concentration in plasma was most pronounced in participants in the top tertile of baseline copeptin. CONCLUSIONS Water supplementation in persons with habitually low water consumption and high copeptin levels is effective in lowering copeptin. It appears a safe and promising intervention with the potential of lowering fasting plasma glucose and thus reducing diabetes risk. Further investigations are warranted to support these findings.
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Evidence that transient changes in sudomotor output with cold and warm fluid ingestion are independently modulated by abdominal, but not oral thermoreceptors.
Morris, NB, Bain, AR, Cramer, MN, Jay, O
Journal of applied physiology (Bethesda, Md. : 1985). 2014;(8):1088-95
Abstract
Two studies were performed to 1) characterize changes in local sweat rate (LSR) following fluid ingestion of different temperatures during exercise, and 2) identify the potential location of thermoreceptors along the gastrointestinal tract that independently modify sudomotor activity. In study 1, 12 men cycled at 50% Vo2peak for 75 min while ingesting 3.2 ml/kg of 1.5°C, 37°C, or 50°C fluid 5 min before exercise; and after 15, 30, and 45-min of exercise. In study 2, 8 men cycled at 50% Vo2peak for 75 min while 3.2 ml/kg of 1.5°C or 50°C fluid was delivered directly into the stomach via a nasogastric tube (NG trials) or was mouth-swilled only (SW trials) after 15, 30, and 45 min of exercise. Rectal (Tre), aural canal (Tau), and mean skin temperature (Tsk); and LSR on the forehead, upper-back, and forearm were measured. In study 1, Tre, Tau, and Tsk were identical between trials, but after each ingestion, LSR was significantly suppressed at all sites with 1.5°C fluid and was elevated with 50°C fluid compared with 37°C fluid (P < 0.001). The peak difference in mean LSR between 1.5°C and 50°C fluid after ingestion was 0.29 ± 0.06 mg·min(-1)·cm(-2). In study 2, LSR was similar between 1.5°C and 50°C fluids with SW trials (P = 0.738), but lower at all sites with 1.5°C fluid in NG trials (P < 0.001) despite no concurrent differences in Tre, Tau, and Tsk. These data demonstrate that 1) LSR is transiently altered by cold and warm fluid ingestion despite similar core and skin temperatures; and 2) thermoreceptors that independently and acutely modulate sudomotor output during fluid ingestion probably reside within the abdominal area, but not the mouth.
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Fluid intake and changes in limb volumes in male ultra-marathoners: does fluid overload lead to peripheral oedema?
Bracher, A, Knechtle, B, Gnädinger, M, Bürge, J, Rüst, CA, Knechtle, P, Rosemann, T
European journal of applied physiology. 2012;(3):991-1003
Abstract
An increase in body mass due to oedema has been previously described. The aim of this study was to investigate a potential association between both fluid and electrolyte intake and the formation of peripheral oedemas. Fluid and electrolyte intakes and the changes in limb volumes in 50 male 100-km ultra-marathoners were measured. Pre- and post-race serum sodium concentration ([Na(+)]), serum aldosterone concentration, serum copeptin concentration, serum and urine osmolality and body mass were determined. Fluid intake, renal function parameters and urinary output, as well as the changes of volume in the extremities, were measured. The changes of volume in the limbs were measured using plethysmography. Serum [Na(+)] increased by 1.6%; body mass decreased by 1.9 kg. Serum copeptin and aldosterone concentrations were increased. The change in serum copeptin concentration and the change in serum [Na(+)] correlated positively; the change in serum [Na(+)] and body mass correlated negatively. A mean fluid intake of 0.58 L/h was positively related to running speed and negatively to post-race serum [Na(+)]. Total fluid intake was positively related to the changes in both arm and lower leg volumes. Running speed was positively associated with the changes in arm and lower leg volumes; race time was related to the changes in serum copeptin or aldosterone concentrations. To conclude, fluid intake was related to the changes in limb volumes, where athletes with an increased fluid intake developed an increase in limb volumes.
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Trained humans can exercise safely in extreme dry heat when drinking water ad libitum.
Nolte, HW, Noakes, TD, Van Vuuren, B
Journal of sports sciences. 2011;(12):1233-41
Abstract
Guidelines to establish safe environmental exercise conditions are partly based on thermal prescriptive zones. Yet there are reports of self-paced human athletic performances in extreme heat. Eighteen participants undertook a 25-km route march in a dry bulb temperature reaching 44.3°C. The mean (± s) age of the participants was 26.0 ± 3.7 years. Their mean ad libitum water intake was 1264 ± 229 mL · h(-1). Predicted sweat rate was 1789 ± 267 mL · h(-1). Despite an average body mass loss of 2.73 ± 0.98 kg, plasma osmolality and serum sodium concentration did not change significantly during exercise. Total body water fell 1.47 kg during exercise. However, change in body mass did not accurately predict changes in total body water as a 1:1 ratio. There was a significant relationship (negative slope) between post-exercise serum sodium concentration and changes in both body mass and percent total body water. There was no relationship between percent body mass loss and peak exercise core temperature (39 ± 0.9°C) or exercise time. We conclude that participants maintained plasma osmolality, serum sodium concentration, and safe core temperatures by (1) adopting a pacing strategy, (2) high rates of ad libitum water intake, and (3) by a small reduction in total body water to maintain serum sodium concentration. Our findings support the hypothesis that humans are the mammals with the greatest capacity for exercising in extreme heat.
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Potential impact of a 500-mL water bolus and body mass on plasma osmolality dilution.
Sollanek, KJ, Kenefick, RW, Cheuvront, SN, Axtell, RS
European journal of applied physiology. 2011;(9):1999-2004
Abstract
A methodological discrepancy exists in the hydration assessment literature regarding the establishment of euhydration, as some investigations utilize a pre-hydration technique, while others do not (overnight fluid/food fast). However, the degree that plasma osmolality (P (osm)) dilutes when using the pre-hydration method and how body mass/composition might influence the results is not known. Thirty subjects (22 M, 8 F; 20 ± 2 years (mean ± SD); 1.8 ± 0.1 m; 75.8 ± 13.5 kg) had P (osm) measured after an 8-h food and fluid fast (overnight fast) and 90 min after a 500-mL (4-9 mL/kg) water bolus (pre-hydration). From pre- to post-bolus, participants' P (osm) declined from 297 ± 3.5 to 295 ± 3.8 mmol/kg (p < 0.05; ∆ -1.7 ± 3.5 mmol/kg). One-third of the sample diluted to more than -3 mmol/kg. The effect of body mass on P (osm) dilution was investigated by comparing dilution in the ten lightest (62.8 ± 3.4 kg) and heaviest (92.0 ± 9.8 kg) participants; however, the change between the light (∆ -1.9 ± 3.8 mmol/kg) versus heavy groups (∆ -1.1 ± 3.0 mmol/kg) was not different (p > 0.05). The correlation between body mass or total body water and change in P (osm) was weak (p > 0.05), as was the correlation between relative fluid intake based on mass and change in P (osm) (p > 0.05). The two methodologies appear to produce similar P (osm) values when measured in most individuals. However, the potential for significant dilution (>3 mmol/kg) should be considered when choosing the pre-hydration methodology.
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Gastric emptying after pickle-juice ingestion in rested, euhydrated humans.
Miller, KC, Mack, GW, Knight, KL
Journal of athletic training. 2010;(6):601-8
Abstract
CONTEXT Small volumes of pickle juice (PJ) relieve muscle cramps within 85 seconds of ingestion without significantly affecting plasma variables. This effect may be neurologic rather than metabolic. Understanding PJ's gastric emptying would help to strengthen this theory. OBJECTIVE To compare gastric emptying and plasma variables after PJ and deionized water (DIW) ingestion. DESIGN Crossover study. SETTING Laboratory. PATIENTS OR OTHER PARTICIPANTS Ten men (age = 25.4 ± 0.7 years, height = 177.1 ± 1.6 cm, mass = 78.1 ± 3.6 kg). INTERVENTION(S): Rested, euhydrated, and eunatremic participants ingested 7 mL·kg⁻¹ body mass of PJ or DIW on separate days. MAIN OUTCOME MEASURE(S): Gastric volume was measured at 0, 5, 10, 20, and 30 minutes postingestion (using the phenol red dilution technique). Percentage changes in plasma volume and plasma sodium concentration were measured preingestion (-45 minutes) and at 5, 10, 20, and 30 minutes postingestion. RESULTS Initial gastric volume was 624.5 ± 27.4 mL for PJ and 659.5 ± 43.8 mL for DIW (P > .05). Both fluids began to empty within the first 5 minutes (volume emptied: PJ = 219.2 ± 39.1 mL, DIW = 305.0 ± 40.5 mL, P < .05). Participants who ingested PJ did not empty further after the first 5 minutes (P > .05), whereas in those who ingested DIW, gastric volume decreased to 111.6 ± 39.9 mL by 30 minutes (P < .05). The DIW group emptied faster than the PJ group between 20 and 30 minutes postingestion (P < .05). Within 5 minutes of PJ ingestion, plasma volume decreased 4.8% ± 1.6%, whereas plasma sodium concentration increased 1.6 ± 0.5 mmol·L⁻¹ (P < .05). Similar changes occurred after DIW ingestion. Calculated plasma sodium content was unchanged for both fluids (P > .05). CONCLUSIONS The initial decrease in gastric volume with both fluids is likely attributable to gastric distension. Failure of the PJ group to empty afterward is likely due to PJ's osmolality and acidity. Cardiovascular reflexes resulting from gastric distension are likely responsible for the plasma volume shift and rise in plasma sodium concentration despite nonsignificant changes in plasma sodium content. These data support our theory that PJ does not relieve cramps via a metabolic mechanism.
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Effects of encouraged water drinking on thermoregulatory responses after 20 days of head-down bed rest in humans.
Sato, M, Kanikowska, D, Iwase, S, Shimizu, Y, Inukai, Y, Nishimura, N, Sugenoya, J
International journal of biometeorology. 2009;(5):443-9
Abstract
We tested the hypothesis that encouraged water drinking according to urine output for 20 days could ameliorate impaired thermoregulatory function under microgravity conditions. Twelve healthy men, aged 24 +/- 1.5 years (mean +/- SE), underwent -6 degrees head-down bed rest (HDBR) for 20 days. During bed rest, subjects were encouraged to drink the same amount of water as the 24-h urine output volume of the previous day. A heat exposure test consisting of water immersion up to the knees at 42 degrees C for 45 min after a 10 min rest (baseline) in the sitting position was performed 2 days before the 20-day HDBR (PRE), and 2 days after the 20-day HDBR (POST). Core temperature (tympanic), skin temperature, skin blood flow and sweat rate were recorded continuously. We found that the -6 degrees HDBR did not increase the threshold temperature for onset of sweating under the encouraged water drinking regime. We conclude that encouraged water drinking could prevent impaired thermoregulatory responses after HDBR.
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Description of self-reported fluid intake and its effects on body weight, symptoms, quality of life and physical capacity in patients with stable chronic heart failure.
Holst, M, Strömberg, A, Lindholm, M, Willenheimer, R
Journal of clinical nursing. 2008;(17):2318-26
Abstract
AIM: To describe the self-reported fluid intake and its effects on body weight, signs and symptoms of heart failure, quality of life, physical capacity and thirst, in patients with stabilised chronic heart failure. BACKGROUND Patients with chronic heart failure are often recommended a fluid restriction of 1.5 l/day but there is no evidence in the literature for this recommendation and little is known about the fluid intake consequences. DESIGN Crossover study. METHODS Chronic heart failure patients, clinically stabilised after an unstable state, were randomised to a 32-week cross-over study assessing the clinical importance of fluid prescription. In a secondary analysis of 63 patients, efficacy variables were analysed in relation to the self-reported median fluid intake of 19 ml/kg body weight/day. RESULTS The mean fluid intake was 16 ml/kg/day in the below-median group and 24 ml/kg/day in the above-median group. No between-group differences were found in change in body weight, signs and symptoms, diuretic use, quality of life or physical capacity. However, the above-median group significantly decreased sense of thirst and difficulties to adhere to the fluid prescription compared with the below-median group. CONCLUSION In clinically stabilised chronic heart failure patients on optimal pharmacological treatment, a larger fluid intake was associated with decreasing thirst without any measurable negative effects on signs and symptoms of heart failure, diuretic use or physical capacity. Thus, a more liberal fluid intake may be advisable in chronic heart failure patients who have been stabilised after an initial unstable clinical state. RELEVANCE TO CLINICAL PRACTICE Nurses involved in the care for patients with heart failure known how troublesome thirst can be and how difficult it can be to follow a restricted fluid intake. This study indicates that it is possible to reassess and recommend a less strict fluid intake in stabilised patients with chronic heart failure.
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Diminished glucocorticoid negative feedback in polydipsic hyponatremic schizophrenic patients.
Goldman, MB, Wood, G, Goldman, MB, Gavin, M, Paul, S, Zaheer, S, Fayyaz, G, Pilla, RS
The Journal of clinical endocrinology and metabolism. 2007;(2):698-704
Abstract
CONTEXT The mechanism and significance of diminished glucocorticoid negative feedback in schizophrenia is unknown but is more commonly observed in schizophrenic patients with primary polydipsia. Polydipsic patients, especially those who are also hyponatremic, exhibit other neuroendocrine abnormalities that have been linked to hippocampal pathology. OBJECTIVE The objective of the study was to determine the effect of cortisol on plasma ACTH under conditions thought to be most sensitive to hippocampal influences. DESIGN The design was repeated measures. SETTING The study was conducted at an inpatient clinical research center. PARTICIPANTS Participants included eight polydipsic hyponatremic and eight polydipsic normonatremic as well as six schizophrenic patients without water imbalance. Eight healthy community volunteers matched for age and gender were also studied. INTERVENTION Metyrapone (750 mg) was administered orally at 1430 and 1900 h. Beginning at 1930 h, hydrocortisone was infused over 150 min at 0.03 mg/kg.h. Blood samples and other measures were obtained at 20-min intervals from 1850 to 2320 h. MAIN OUTCOME MEASURES Plasma ACTH and cortisol were measured. RESULTS ACTH levels did not decline significantly during the cortisol infusion in the polydipsic hyponatremic group. For any given level of cortisol, ACTH levels were higher in the hyponatremic group. Although levels declined after cortisol in the other three groups, the decline was greatest in patients without water imbalance. CONCLUSIONS The marked impairment in glucocorticoid negative feedback in polydipsic hyponatremic schizophrenic patients is consistent with hippocampal mineralocorticoid dysfunction.