ECSS Paris 2023: CP-PN21
INTRODUCTION: There are well-understood ethnic differences among Americans in hemodynamics and metabolic health, while NHANES fluid intake data suggests certain ethnic groups are at greater risk for hypohydration. Recent evidence suggests that young African American (AA) adults may be more likely than young Caucasian adults to be hypohydrated, with reduced urine output, increased urine specific gravity, and elevated copeptin (1). It is generally accepted that dehydration is associated with diminished exercise performance, but less is known about the potential impact of hypohydration on non-exercise physical exertion. Therefore, we evaluated physical function capacity, hydration status and Quality of Life indicators in a multi-ethnic cohort of American women. METHODS: Healthy women (n=114) aged 19-70 yrs were enrolled from the San Francisco metropolitan area without preference for ethnicity. Health was defined as absence of chronic disease and no recent use of associated medications (e.g., insulin, diuretics, corticosteroids). Vitals were measured, and participants completed the PROMIS-29 QoL questionnaire. Fasted blood was collected and glucose, ADH, and copeptin were analyzed. Twenty-four-hour urine volume was collected, and urine was analyzed for osmolality, specific gravity, and creatinine. A two-way ANOVA was used to detect differences in means between ethnicities. All data are expressed as mean ± SEM. RESULTS: The cohort was comprised of Asian (n=51), African American (n = 24), Caucasian (n=21), and Hispanic (n=18) ethnicities. AA women had the highest BMI (33.25; p<0.0001) and highest systolic BP (124.54±3.18 mm Hg), while there were no differences in glucose or urine volume. There were group effects for ethnicity on PROMIS Physical Function (p=0.007), urine specific gravity (p=0.007), urine creatinine (p<0.0001), and ADH (p<0.001). AA women had the lowest aggregate score on the physical function domain (13.58±1.63), indicating more difficulty with activities of daily living . AA women had higher urine specific gravity (1.02±0.01) and markedly elevated urine creatinine (161.11±19.77 mg/dL). AA women had elevated ADH (27.31±2.53 pg/mL), and while not statistically significant, the highest mean level of copeptin. CONCLUSION: In this cross-sectional sample, AA women reported the lowest physical function capacity, while displaying multiple indicators of hypohydration and possible renal insufficiency. These findings could be in part related to differences in body composition. Hydration interventions targeted to specific ethnicities may have potential to improve free-living hydration status, kidney function, and capacity for physical activity. 1. Robinson AT, et al. Am J Clin Nutr. 2023 Oct;118(4):822-833.
Read CV Berk EvanECSS Paris 2023: CP-PN21
INTRODUCTION: Several studies have examined the effects of hydration, identifying optimal solutions for maintaining hydration status. However, these studies controlled the amount and timing of fluid intake, thereby excluding the behavioral component. In real-world situations, drinking behavior plays a crucial role in determining fluid intake patterns, ultimately influencing hydration efficacy—yet this aspect remains insufficiently explored. In this context, our previous research demonstrated that carbonated water ingestion can alter perceptions such as exhilaration, sleepiness, and/or stimulating feeling both at rest (Fujii et al., 2022) and following exercise (Kajiki et al., 2024) in the heat. These perceptual changes may influence drinking behavior and, consequently, hydration effectiveness. However, this relationship has not been directly investigated. METHODS: Eight healthy young adults performed repeated 10-min cycling bouts at 50% peak oxygen uptake in a hot environment (35ºC), interspersed with 3-min passive recovery periods, until a 2% reduction in body mass was achieved. Twenty min after the exercise, participants were transferred to another room maintained at 25ºC. They then freely consumed one of three beverages: (1) water, (2) carbonated water, or (3) a sports drink, over a 30-min period. Each beverage trial was conducted on separate days and the order was randomized and counterbalanced. Venous blood samples were collected pre-exercise, immediately post-exercise (0 min), and at 30 and 60 min after the commencement of drinking. Urine samples were obtained pre-exercise, immediately post-exercise, and at 30 min, 1 h, 2 h, 3 h, and 4 h following the onset of drinking. RESULTS: During the initial 5 min of the 30-min ad libitum drinking period, the volume of beverage consumed was lower for carbonated water compared to the other two beverages. Similarly, the total volume ingested over the entire 30-min period tended to be lower for carbonated water than for water or the sports drink. Despite the differences in fluid intake, no significant differences were observed in urine output, plasma volume, plasma osmolality, or vasopressin levels among the three beverage conditions at any time point. CONCLUSION: In healthy young individuals, carbonation of beverage reduces initial beverage consumption, likely due to sensory effects associated with carbonation (e.g., oral stimulation). However, despite this attenuation in early fluid intake, hydration efficiency appears comparable to that of water and sports drinks. Carbonated water may serve as a potential strategy to mitigate overhydration, particularly in individuals with lower sweat rates, though this hypothesis requires further investigation.
Read CV Naoto FujiiECSS Paris 2023: CP-PN21
INTRODUCTION: The Beverage Hydration Index (BHI) allows comparison of fluid retention profiles for different beverages relative to water. The impact of caffeine with and without electrolytes on hydration status over 4 hours is not well characterized. The effects of commercially available caffeinated beverages were compared to water (W) on hydration measures to understand the impact of various formulations on hydration status over 4 hours in a sedentary & euhydrated state. This study aimed to provide more clarity on the impact of different caffeinated products and their ability to promote fluid retention or diuresis. METHODS: 28 healthy adults (14M/14F; age 22.6±3 y) participated in a BHI protocol. Participants arrived to the lab in a euhydrated state which was confirmed by urine specific gravity. Beverages were then administered in a randomized order of four 250mL aliquots over 30min: 500ml of caffeinated beverage (CAF) with 280mg, CAF of 280mg plus electrolytes (CAF+E) or CAF with 100mg+E & carbohydrates (CAF+CE) along with 500ml W (1st & 4th aliquot). Urine output was recorded over 4hr. RESULTS: W & CAF+CE averaged a more positive net fluid balance (NFB) (p<0.001, 0.001) compared to CAF & CAF+E, ranging from 120 to 175ml greater overall fluid balance. From 60–240min, CAF+CE exhibited significantly higher NFB when compared to CAF & CAF+E (P<0.05). From 120-240min, CAF+CE had significantly higher BHI scores when compared to CAF & CAF+E (P<0.05). CAF+CE had significantly lower urine output when compared to CAF & CAF+E from 90-240min (P<0.05). CONCLUSION: A low carbohydrate-electrolyte beverage with moderate levels of caffeine (CAF+CE) had similar hydration properties compared to water and both were significantly greater than CAF and CAF+E. Based on BHI, CAF+CE retained ~10 and 15% more fluid when compared to CAF+E and CAF, respectively, which has practical implications for caffeine containing products. This data suggests that a low -carbohydrate- electrolyte beverage with added caffeine may attenuate diuresis in a hydrating energy drink solution.
Read CV Michael LelkoECSS Paris 2023: CP-PN21