Hemodynamic and Body Fluid Response to Water Ingestion

Despite a paucity of information regarding the hemodynamic changes associated with moderate fluid ingestion, the popular, unsubstantiated recommendation for most adults to ingest 8 x 8 ounce glasses of water daily (1888 mL) remains prevalent. PURPOSE: The purpose of this study was to determine the hemodynamic and body fluid changes associated with consuming water at temperatures of 4° C & 37° C and two volumes of 7 & 21 mL/kg. METHODS: 10 subjects (age 22.3 ± 1.3 yr, ht. 1.74 ± .15 m., body mass(bm), 75.1 ± 18.5 kg, 4♂) reported to the lab in a euhydrated state and refrained from ingestion of food and beverage (except water) for 10 hrs and no water 2 hours pre- trial. 30 minutes of rest preceded venipuncture for hematocrit (H), plasma specific gravity (PSG), and plasma density (PD) analyzed by digital refractometry. Hemodynamic values of heart rate (HR), stroke volume (SV) and cardiac output (Q) were obtained by a non-invasive impedance cardiography system. All measures were obtained pre-water ingestion (PRE) and at 20 minute intervals following water ingestion (T1, T2, & T3). Immediately following the PRE, subjects ingested C7, C21, H7 or H21 with the volume calculated from individual bm at a mean of 526 and 1577 mL for 7 and 21 trials, respectively. Subjects served as their own control in the randomized assignment of trials. RESULTS: Statistical analysis by ANOVA was applied to these data and revealed NSD (p>.05) among all trials. Mean values for all four trials are depicted in the following table:Table: No title available.CONCLUSION: The ingestion of water in volumes and temperatures mimicking current practices among many adults results in minimal expansion of blood volume or changes in hemodynamic function. Apparently, consuming considerable water without excessive loss of fluid from either environmental conditions or exercise induced temperature regulation, is safe with no adverse impact on non-exercising individuals.