Using a randomized order for beverage treatments at three separate trials, subjects will ingest 1 Liter of one of three beverages in 10 minutes: water, a beverage with 2.5% glucose with 45 mmol sodium/L, or a beverage with 1.7% glucose with 60 mmol sodium/L. Before and repeatedly for 2 h after ingestion of the beverage, blood samples will be drawn for assessments of D2O, Hb, Hct, osmolality, sodium, and glucose. The rate of appearance of D2O will be evaluated using the area under the curve, the slope of the appearance, and half time to plateau. Comparisons will be made between beverages for indices of the rate of appearance of D2O, the change in PV over time, and cumulative urine excreted. The cumulative urine produced will be used to calculate a modified BHI for the two glucose-electrolyte beverages and water for comparison with 1.0 (expected for no beverage effect). We hypothesize faster absorption (D2O appearance rate), and better overall hydration (expanded PV and higher modified BHI) will occur for beverages containing glucose and sodium compared to water. Further, we hypothesize that of the electrolyte beverages, the beverage with higher sodium content will promote greater overall hydration (less urine excreted) than the beverage with lower sodium.
The study examines interactions between fluid availability in the gut and fluid retention in the body. The relative rate of fluid uptake, the expansion of the plasma volume, and percent of fluid retained by the body will be measured in response to ingestion of beverages of different composition. Healthy, euhydrated adults will be studied. The results will help establish formulations of beverages that sustain if not promote acute euhydration.