A randomized trial to assess beverage hydration index in healthy older adults

Rehydration effect of qingshu buye decoction on exercise and high temperature-induced dehydration

OBJECTIVE

The aim of this study was to conduct a comprehensive evaluation of the rehydration efficacy of QSBYD and elucidate its potential underlying mechanism.

DESIGN

38 participants were randomly assigned to receive either QSBYD or placebo before and after exercise and heat-induced dehydration. Hydration indicators were measured over time. Blood tests assessed cellular anaerobic respiration metabolites, serum inflammatory markers, and coagulation markers. Perceptual measures of thirst, fatigue, and muscular soreness were also taken.

RESULTS

QSBYD consumption resulted in lower urine volume (Control vs. QSBYD: 260.83 ± 167.99 ml vs. 187.78 ± 141.34 ml) and smaller decrease in percentage of nude body weight change from baseline (Control vs. QSBYD: -0.52 ± 0.89% vs. -0.07 ± 0.52%). Although no significant differences in urine specific gravity, QSBYD resulted in reduced urine volume at 120 min, suggesting improved fluid retention. Furthermore, QSBYD resulted in lower levels of IL-1β (Control vs. QSBYD: 2.40 ± 0.68 vs. 1.33 ± 0.66 pg/mL), suggesting QSBYD may provide benefits beyond hydration.

CONCLUSION

Further investigation into the underlying mechanisms and long-term effects of QSBYD on hydration is warranted. QSBYD may be an effective alternative to commercial sports drinks in mitigating dehydration effects.

Randomized Trial to Assess the Safety and Tolerability of Daily Intake of an Allulose Amino Acid-Based Hydration Beverage in Men and Women

BACKGROUND

Maintaining adequate hydration is critical to optimal health, well-being, and performance. Those who are physically active in stressful environments, such as warm and/or humid scenarios, may be at particular risk for dehydration with ensuing loss of electrolytes, leading to sluggishness and impaired physical performance.

METHODS

We evaluated an electrolyte and amino acid product containing L-alanine and L-glutamine, as well as select vitamins [B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B12 (cobalamin), and vitamin C (ascorbic acid)]. Subjects (n = 40; four groups, n = 10) were randomized to consume either a placebo packet or one, two, or three packets daily of the test product for 4 weeks with site visits at 0, 2, and 4 weeks. We tested safety and tolerability by analyzing hematological parameters (complete blood counts), metabolic parameters (hepatic, renal, acid-base balance), urinalysis end products, thyroid status [T3 (triiodothyronine), T4 (thyroxine), TSH (thyroid-stimulating hormone)], tolerability (via questionnaire), vital signs, and dietary intake.

RESULTS

Statistical analyses displayed ten significant main effects (p < 0.05) with white blood cells, lymphocytes, neutrophils, urinary pH, thyroxine, urination frequency, calcium, calories, fat, and cholesterol. Interactions for time and group (p < 0.05) were observed for MCV, eGFR, potassium, overall tolerability, bloating, and cramping-demonstrating mild GA disturbances. Little to no change of physiological relevance was noted for any outcome variable, regardless of dosing level.

CONCLUSIONS

Our results indicate the product was well-tolerated at all dosing levels and no significant adverse changes occurred in any of the test parameters compared to the placebo group, indicating relative safety of ingestion over a 4-week treatment period, at the volumes used, and outside the context of physical stress.

Iterative assessment of a sports rehydration beverage containing a novel amino acid formula on water uptake kinetics

PURPOSE

Rapid gastric emptying and intestinal absorption of beverages is essential for rapid rehydration, and certain amino acids (AA) may augment fluid delivery. Three sugar-free beverages, containing differing AA concentrations (AA + PZ), were assessed for fluid absorption kinetics against commercial sugar-free (PZ, GZ) and carbohydrate-containing (GTQ) beverages.

METHODS

Healthy individuals (n = 15-17 per study) completed three randomised trials. Three beverages (550-600 mL) were ingested in each study (Study 1: AA + PZ [17.51 g/L AA], PZ, GZ; Study 2: AA + PZ [6.96 g/L AA], PZ, GZ; Study 3: AA + PZ [3.48 g/L AA], PZ, GTQ), containing 3.000 g deuterium oxide (D2O). Blood samples were collected pre-, 2-min, 5-min, and every 5-min until 60-min post-ingestion to quantify maximal D2O enrichment (Cmax), time Cmax occurred (Tmax) and area under the curve (AUC).

RESULTS

Study 1: AUC (AA + PZ: 15,184 ± 3532 δ‰ vs. VSMOW; PZ: 17,328 ± 3153 δ‰ vs. VSMOW; GZ: 17,749 ± 4204 δ‰ vs. VSMOW; P ≤ 0.006) and Tmax (P ≤ 0.005) were lower for AA + PZ vs. PZ/GZ. Study 2: D2O enrichment characteristics were not different amongst beverages (P ≥ 0.338). Study 3: Cmax (AA + PZ: 440 ± 94 δ‰ vs. VSMOW; PZ: 429 ± 83 δ‰ vs. VSMOW; GTQ: 398 ± 81 δ‰ vs. VSMOW) was greater (P = 0.046) for AA + PZ than GTQ, with no other differences (P ≥ 0.106).

CONCLUSION

The addition of small amounts of AA (3.48 g/L) to a sugar-free beverage increased fluid delivery to the circulation compared to a carbohydrate-based beverage, but greater amounts (17.51 g/L) delayed delivery.

Trends and Missing Links in (De)Hydration Research: A Narrative Review

Despite decades of literature on (de)hydration in healthy individuals, many unanswered questions remain. To outline research and policy priorities, it is fundamental to recognize the literature trends on (de)hydration and identify current research gaps, which herein we aimed to pinpoint. From a representative sample of 180 (de)hydration studies with 4350 individuals, we found that research is mainly limited to small-scale laboratory-based sample sizes, with high variability in demographics (sex, age, and level of competition); to non-ecological (highly simulated and controlled) conditions; and with a focus on recreationally active male adults (e.g., Tier 1, non-athletes). The laboratory-simulated environments are limiting factors underpinning the need to better translate scientific research into field studies. Although, consistently, dehydration is defined as the loss of 2% of body weight, the hydration status is estimated using a very heterogeneous range of parameters. Water is the most researched hydration fluid, followed by alcoholic beverages with added carbohydrates (CHO). The current research still overlooks beverages supplemented with proteins, amino acids (AA), and glycerol. Future research should invest more effort in "real-world" studies with larger and more heterogeneous cohorts, exploring the entire available spectrum of fluids while addressing hydration outcomes more harmoniously.

Compositional Aspects of Beverages Designed to Promote Hydration Before, During, and After Exercise: Concepts Revisited

Hypohydration can impair aerobic performance and deteriorate cognitive function during exercise. To minimize hypohydration, athletes are recommended to commence exercise at least euhydrated, ingest fluids containing sodium during long-duration and/or high-intensity exercise to prevent body mass loss over 2% and maintain elevated plasma osmolality, and rapidly restore and retain fluid and electrolyte homeostasis before a second exercise session. To achieve these goals, the compositions of the fluids consumed are key; however, it remains unclear what can be considered an optimal formulation for a hydration beverage in different settings. While carbohydrate-electrolyte solutions such as sports drinks have been extensively explored as a source of carbohydrates to meet fuel demands during intense and long-duration exercise, these formulas might not be ideal in situations where fluid and electrolyte balance is impaired, such as practicing exercise in the heat. Alternately, hypotonic compositions consisting of moderate to high levels of electrolytes (i.e., ≥45 mmol/L), mainly sodium, combined with low amounts of carbohydrates (i.e., <6%) might be useful to accelerate intestinal water absorption, maintain plasma volume and osmolality during exercise, and improve fluid retention during recovery. Future studies should compare hypotonic formulas and sports drinks in different exercise settings, evaluating different levels of sodium and/or other electrolytes, blends of carbohydrates, and novel ingredients for addressing hydration and rehydration before, during, and after exercise.

Effect of fluid replacement with green tea on body fluid balance and renal responses under mild thermal hypohydration: a randomized crossover study

PURPOSE

Maintaining an appropriate hydration level by ingesting fluid in a hot environment is a measure to prevent heat-related illness. Caffeine-containing beverages, including green tea (GT), have been avoided as inappropriate rehydration beverages to prevent heat-related illness because caffeine has been assumed to exert diuretic/natriuretic action. However, the influence of caffeine intake on urine output in dehydrated individuals is not well documented. The aim of the present study was to examine the effect of fluid replacement with GT on body fluid balance and renal water and electrolyte handling in mildly dehydrated individuals.

METHODS

Subjects were dehydrated by performing three bouts of stepping exercise for 20 min separated by 10 min of rest. They were asked to ingest an amount of water (H2O), GT, or caffeinated H2O (20 mg/100 ml; Caf-H2O) that was equal to the volume of fluid loss during the dehydration protocol; fluid balance was measured for 2 h after fluid ingestion.

RESULTS

The dehydration protocol induced hypohydration by ~ 10 g/kg body weight (~ 1% of body weight). Fluid balance 2 h after fluid ingestion was significantly less negative in all trials, and the fluid retention ratio was 52.2 ± 4.2% with H2O, 51.0 ± 5.0% with GT, and 47.9 ± 6.2% with Caf-H2O; those values did not differ among the trials. After rehydration, urine output, urine osmolality, and urinary excretions of osmotically active substances, sodium, potassium and chloride were not different among the trials.

CONCLUSION

The data indicate that ingestion of GT or an equivalent caffeine amount does not worsen the hydration level 2 h after ingestion and can be effective in reducing the negative fluid balance for acute recovery from mild hypohydration.

TRIAL REGISTRATION

ISRCTN53057185; retrospectively registered.

A randomised trial to assess fluid and electrolyte balance responses following ingestion of different beverages in young and older men

BACKGROUND

Older adults are susceptible to dehydration and fluid overload due to a reduced ability to maintain homeostatic control of fluid and electrolyte balance.

PURPOSE

To assess fluid and electrolyte balance responses in young and older men following ingestion of commonly consumed beverages differing in composition.

METHODS

12 young and 11 older men were recruited. Euhydrated body mass was recorded. Participants consumed 1L (250 ml every 15 min) of water, fruit juice, a sports drink or low-fat milk in a randomized cross-over design. Urine and blood samples were obtained before and after the drinking period and every hour thereafter for 3-h. Samples were used to determine osmolality, electrolytes (Na+ and K+), water clearance, and glomerular filtration rate.

RESULTS

Free water clearance was significantly higher in Young than Older at 1 and 2 h after the ingestion of W and S (p < 0.05). Net Na+ and K+ balance were not different between Young and Older (p = 0.91 and p = 0.65) adults, respectively. At 3 h Na+ balance was negative after ingesting water and fruit juice, but neutral after sport drink and milk. Net K+ balance was neutral at 3 h after ingesting milk, but negative after water, fruit juice and sport drink.

CONCLUSIONS

Milk was retained longer than other beverages in Young, but not in Older, despite similar net electrolyte balance responses. Older had higher fluid retention in the first 2 h after the ingestion of all beverages, except for milk when compared to Young, indicating an age-related loss of ability to regulate fluid balance under current study conditions.

Post-exercise rehydration: Comparing the efficacy of three commercial oral rehydration solutions

Introduction

This study compared the efficacy of three commercial oral rehydration solutions (ORS) for restoring fluid and electrolyte balance, after exercise-induced dehydration.

Method

Healthy, active participants (N = 20; ♀ = 3; age ∼27 y, V˙O₂peak ∼52 ml/kg/min) completed three randomised, counterbalanced trials whereby intermittent exercise in the heat (∼36°C, ∼50% humidity) induced ∼2.5% dehydration. Subsequently, participants rehydrated (125% fluid loss in four equal aliquots at 0, 1, 2, 3 h) with a glucose-based (G-ORS), sugar-free (Z-ORS) or amino acid-based sugar-free (AA-ORS) ORS of varying electrolyte composition. Urine output was measured hourly and capillary blood samples collected pre-exercise, 0, 2 and 5 h post-exercise. Sodium, potassium, and chloride concentrations in urine, sweat, and blood were determined.

Results

Net fluid balance peaked at 4 h and was greater in AA-ORS (141 ± 155 ml) and G-ORS (101 ± 195 ml) than Z-ORS (-47 ± 208 ml; P ≤ 0.010). Only AA-ORS achieved positive sodium and chloride balance post-exercise, which were greater for AA-ORS than G-ORS and Z-ORS (P ≤ 0.006), as well as for G-ORS than Z-ORS (P ≤ 0.007) from 1 to 5 h.

Conclusion

when provided in a volume equivalent to 125% of exercise-induced fluid loss, AA-ORS produced comparable/superior fluid balance and superior sodium/chloride balance responses to popular glucose-based and sugar-free ORS.

The effects of fluid absorption and plasma volume changes in athletes following consumption of various beverages

BACKGROUND

To verify the hydration effects of oral rehydration solution (ORS) on athletes by comparing the degrees of fluid absorption and plasma volume changes following beverage consumption, including ORS.

METHODS

Thirty-one participants visited the testing laboratory 4 times at 1-week intervals to consume 1 L of beverage (e.g., water, ORS, and two sports drinks [SpD]) for 30 min on each visit. The urine output was measured 4 times at 1 h, 2 h, 3 h, and 4 h after beverage consumption. A blood sample was collected 3 times at 1 h, 2 h, and 3 h after beverage consumption. Body weight was measured once in 4 h after beverage consumption.

RESULTS

Body weight change was smaller for ORS than for water, SpD1, and SpD2 (p < 0.05). Cumulative urine output in 4 h was lower for ORS, SpD1, and SpD2 than for water (p < 0.05), and it was lower for ORS than for SpD2 (p < 0.05). BHI in 4 h was higher for ORS, SpD1, and SpD2 than for water (p < 0.05), and it was higher for ORS than for SpD2 (p < 0.05). There was no significant difference in PVC for different beverages at all test times, i.e.., 1 h, 2 h, and 3 h.

CONCLUSIONS

We evaluated the hydration effects of the consumption of beverages, such as water, SpD, and ORS in athletes. ORS and SpD were more effective than water. A comparison between ORS and SpD showed that the result could vary depending on the type of SpD.

A double-blind clinical trial to compare the efficacy and safety of a multiple amino acid-based ORS with the standard WHO-ORS in the management of non-cholera acute watery diarrhea in infants and young children: "VS002A" trial protocol

BACKGROUND

Diarrhea is the second deadliest disease for under-five children globally and the situation is more serious in developing countries. Oral rehydration solution (ORS) is being used as a standard treatment for acute watery diarrhea for a long time. Our objective is to compare the efficacy of amino acid-based ORS "VS002A" compared to standard glucose-based WHO-ORS in infants and young children suffering from acute non-cholera watery diarrhea.

METHODS

It is a randomized, double-blind, two-cell clinical trial at Dhaka Hospital of icddr,b. A total of 312 male children aged 6-36 months old with acute non-bloody watery diarrhea are included in this study. Intervention arm participants get amino acid-based ORS (VS002A) and the control arm gets standard glucose-based WHO-ORS. The primary efficacy endpoint is the duration of diarrhea in the hospital.

DISCUSSION

Oral rehydration therapy (ORT) with the present ORS formulation has certain limitations - it does not reduce the volume, frequency, or duration of diarrhea. Additionally, the failure of present standard ORS to significantly reduce stool output likely contributes to the relatively limited use of ORS by mothers as they do not feel that ORS is helping their child recover from the episode of diarrhea. Certain neutral amino acids (e.g., glycine, L-alanine, L-glutamine) can enhance the absorption of sodium ions and water from the gut. By using this concept, a shelf-stable, sugar-free amino acid-based hydration medicinal food named 'VS002A' that effectively rehydrates, and improves the barrier function of the bowel following infections targeting the gastrointestinal tract has been developed. If the trial shows significant benefits of VS002A use, this may provide evidence to support consideration of the use of VS002A in the present WHO diarrhea management guidelines. Conversely, if there is no evidence of benefit, these results will reaffirm the current guidelines.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04677296 . Registered on December 21, 2020.

Comparison of hydration efficacy of carbohydrate-electrolytes beverages consisting of isomaltulose and sucrose in healthy young adults: A randomized crossover trial

Isomaltulose is a low glycemic and insulinaemic carbohydrate now used as an alternative sweetener in beverages. However, it remains unclear if hydration status may be impacted differently with the consumption of beverages containing isomaltulose as compared to sucrose, a common beverage sweetener. Thirteen young adults (7 women) consumed 1 L of a carbohydrate beverage (with low electrolyte content) containing either 6.5%-sucrose, 6.5%-isomaltulose, or water within a 15 min period. For each beverage, beverage hydration index (BHI, a composite measure of fluid balance after consuming a test beverage relative to water) was calculated from urine volume produced over a 3 h period following ingestion of the carbohydrate beverages relative to water. The change in plasma volume (ΔPV), blood glucose, and lactate concentrations were assessed every 30 min post-beverage consumption. Isomaltulose ingestion attenuated urine production as compared to water and sucrose (P ≤ 0.005) over the 3 h post-ingestion period. However, no differences were observed between sucrose and water (P = 0.055). BHI was 1.53 ± 0.44 for isomaltulose (P ≤ 0.022 vs. sucrose and water) and 1.20±0.29 for sucrose (P = 0.210 vs. water). A transient reduction in ΔPV was observed following the ingestion of the isomaltulose beverage (at 30 min, P = 0.007 vs. sucrose). Thereafter, no differences in ΔPV between beverages were measured. Increases in blood glucose and lactate, indices of absorption and utility of glucose, were delayed in the isomaltulose as compared to sucrose beverage. In summary, we demonstrated a greater BHI with a carbohydrate-electrolyte beverage containing isomaltulose as compared to sucrose. This may in part be attributed to a delayed absorption of isomaltulose reducing diuresis.

Utility of an Isotonic Beverage on Hydration Status and Cardiovascular Alterations

This study determined the beverage hydration index (BHI) and postprandial cardiac autonomic activity after consuming an isotonic beverage (IB) compared to distilled water (DW). Twenty-two participants (50% female; mean ± SD; age, 27 ± 3 year; height, 169.1 ± 12.6 cm; weight, 73.3 ± 13.8 kg; BF%, 23 ± 10%) completed two experimental trials where they consumed 1 L DW or an IB; after which urine volume and cardiac autonomic activity was measured through 240 min. Cardiac autonomic activity was quantified using heart rate (HR), log transformed heart rate variability measures (root mean square of successive R–R intervals; RMSSD; low frequency, LF; and high frequency, HF) and systolic time intervals (pre-ejection period, PEP). BHI was significantly greater after IB consumption at min 0 (MD [95% CI]; 1.31 [0.35, 2.27]), 180 min (0.09 [0.022, 0.16]), and 240 min (0.1 [0.03, 0.17]) compared to DW (p = 0.031). Net fluid balance was significantly greater in IB than DW at 180 min (90 [−16.80, 196.81]) and 240 min (106 [−13.88, 225.88]) (p = 0.037). HR decreased over time in both beverage trials but was higher following IB ingestion at 0 min (3.9 [−2.42, 10.22]), 30 min (5.3 [−0.94, 11.54]), and 60 min (2.7 [−3.42, 8.82]) (p = 0.0002). lnHF was greater 30 min post DW ingestion compared to IB (0.45 [−0.23, 1.13]) (p = 0.039). IB promotes greater fluid retention capacity compared to DW within 4 hours of consumption. The variations in cardiac autonomic measures may warrant further investigation in clinical populations (i.e., patients with autonomic failure).

The Beverage Hydration Index: Influence of Electrolytes, Carbohydrate and Protein

The beverage hydration index (BHI) facilitates a comparison of relative hydration properties of beverages using water as the standard. The additive effects of electrolytes, carbohydrate, and protein on rehydration were assessed using BHI. Nineteen healthy young adults completed four test sessions in randomized order: deionized water (W), electrolytes only (E), carbohydrate-electrolytes (C + E), and 2 g/L dipeptide (alanyl-glutamine)-electrolytes (AG + E). One liter of beverage was consumed, after which urine and body mass were obtained every 60 min through 240 min. Compared to W, BHI was higher (p = 0.007) for C + E (1.15 ± 0.17) after 120 min and for AG + E (p = 0.021) at 240 min (1.15 ± 0.20). BHI did not differ (p > 0.05) among E, C + E, or AG + E; however, E contributed the greatest absolute net effect (>12%) on BHI relative to W. Net fluid balance was lower for W (p = 0.048) compared to C + E and AG + E after 120 min. AG + E and E elicited higher (p < 0.001) overall urine osmolality vs. W. W also elicited greater reports of stomach bloating (p = 0.02) compared to AG + E and C + E. The addition of electrolytes alone (in the range of sports drinks) did not consistently improve BHI versus water; however, the combination with carbohydrate or dipeptides increased fluid retention, although this occurred earlier for the sports drink than the dipeptide beverage. Electrolyte content appears to make the largest contribution in hydration properties of beverages for young adults when consumed at rest.

Evaluation of Pragmatic Methods to Rapidly Assess Habitual Beverage Intake and Hydration Status in U.S. Collegiate Athletes

Fluid intake recommendations have been established for the athletic population in order to promote adequate hydration. The Beverage Intake Questionnaire (BEVQ-15) is a quick and reliable food frequency questionnaire that quantifies habitual beverage intake, which has been validated in children, adolescents, and adults. However, no validated beverage consumption questionnaire is available for collegiate athletes. Urine color (UC), while feasible for determining hydration status, has not been validated within a variety of collegiate athletes. The purpose of this investigation was to evaluate the comparative validity and reliability of pragmatic methods to rapidly assess BEVQ-15 and UC rating in U.S. Division I collegiate athletes. Student-athletes (n = 120; 54% females; age 19 ± 1 years) from two universities were recruited to complete three study sessions. At the first and third sessions, the participants completed the BEVQ-15 and provided a urine sample to determine UC and urinary specific gravity. All sessions included completion of a 24-hr dietary recall. Total fluid intake (fl oz) was 111 ± 107 and 108 ± 42 using the BEVQ-15 and the mean of three 24-hr dietary recalls, respectively, which was not different between methods (p > .05). There were moderate associations between the BEVQ-15 and dietary recall results for total beverage intake fl oz and kcal(r = .413 and r = 4.65; p ≤ .05, respectively). Strong associations were noted between both researcher-rated and participant-rated UC with urinary specific gravity measures (r = .675 and r = .884; p ≤ .05, respectively). Therefore, these rapid assessment methods demonstrated acceptable validity and may be used as practical methods to determine whether athletes are meeting their hydration recommendations.

Impact of Nuun Electrolyte Tablets on Fluid Balance in Active Men and Women

Background: Maintaining adequate hydration is important for overall health and has major implications for athletes involved in physically demanding tasks. While water is viewed as an effective means to rehydrate, and is inexpensive and readily available, electrolyte beverages appear to be more beneficial, in particular for athletes who routinely lose electrolytes through sweating. Nuun tablets contain a mix of electrolytes and are quickly dissolved in water to create an electrolyte-rich beverage. We determined the impact of Nuun tablets on the fluid balance of healthy, exercise-trained men and women at rest. Methods: Eight men (25.9 ± 4.5 yrs) and 10 women (28.2 ± 9.4 yrs) ingested either water only or water with Nuun electrolyte tablets, at both a single and double strength concentration, in random order, on three occasions separated by approximately one week, in a fasted and euhydrated state. A total of 1 L of fluid was ingested at each visit over a 30 min period. Urine was collected from each subject at 0, 1, 2, 3, and 4 h post-ingestion. Urine mass values were used to calculate fluid balance and the beverage hydration index (BHI; i.e., the volume of urine produced after drinking the Nuun beverages, relative to that of water only—control condition). Heart rate and blood pressure were measured throughout the four-hour period, while body weight was measured at the start and end of the experiment. Results: Neither heart rate nor blood pressure were impacted by beverage consumption. Nuun tablets resulted in a lower urine output compared to water, with fluid balances for both concentrations more favorable compared to water (p < 0.05), beginning at 2 h post-ingestion and continuing at the 3 h and 4 h times. Body weight loss was less with Nuun at the single dose (0.38 kg; p = 0.02) and double dose (0.43 kg; p = 0.08), compared to water (0.57 kg). The BHI was higher for Nuun (single dose in particular) compared to water at both 2 h (p = 0.05) and 4 h (p = 0.02). Conclusion: The addition of Nuun electrolyte tablets to water improves the fluid balance and BHI in healthy men and women. Results were similar for both concentrations, suggesting that additional electrolytes are not necessary when in a rested state. Future studies should determine the impact of various concentrations of the Nuun beverage during physical exercise—in particular, exercise in the heat, when sweat loss may be highest.

Hydration Efficacy of a Milk Permeate-Based Oral Hydration Solution

Milk permeate is an electrolyte-rich, protein- and fat-free liquid with a similar carbohydrate and mineral content to that of milk. Its hydration efficacy has not been examined. The beverage hydration index (BHI) has been used to compare various beverages to water in terms of post-ingestion fluid balance and retention. Our purpose was to compare the BHI (and related physiological responses) of a novel milk permeate solution (MPS) to that of water and a traditional carbohydrate–electrolyte solution (CES). Over three visits, 12 young subjects consumed 1 L of water, CES, or MPS. Urine samples were collected immediately post-ingestion and at 60, 120, 180, and 240 min. BHI was calculated by dividing cumulative urine output after water consumption by cumulative urine output for each test beverage at each time point. The BHI for MPS was significantly higher at all time points compared to water (all p < 0.001) and CES (all p ≤ 0.01) but did not differ between CES and water at any time point. Drinking 1 L of MPS resulted in decreased cumulative urine output across the subsequent 4 h compared to water and CES, suggesting that a beverage containing milk permeate is superior to water and a traditional CES at sustaining positive fluid balance post-ingestion.