Efficacy of Hydration Beverages in Prolonging Positive Fluid Balance in Young and Older Adults

Open Access
- Author:
- Clarke, Megan Michelle
- Graduate Program:
- Kinesiology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 12, 2018
- Committee Members:
- W. Larry Kenney, Thesis Advisor/Co-Advisor
Lacy Marie Alexander, Committee Member
Jinger Gottschall, Committee Member
Anna E. Stanhewicz, Committee Member - Keywords:
- oral rehydration solution
net fluid balance
beverage hydration index
hydration - Abstract:
- When mild-to-moderate dehydration is suspected in the elderly, glucose-based beverages are often prescribed because glucose-sodium (Na+) cotransporters in the small intestine facilitate active transport of Na+ and resultant water diffusion to the vascular space. Alternatively, amino acid (AA)-based beverages use AA-Na+ cotransporters to facilitate increases in vascular volume in the short-term with potentially fewer negative GI issues (which are often seen in older adults). We aimed to compare the effects of five hydration beverages on short term fluid balance in young and older adults after an overnight fast. We hypothesized that (1) following fluid ingestion, older subjects would stay in positive fluid balance longer than young subjects due to decreased renal excretion rates, and (2) consumption of glucose- or AA-based hydration beverages would further delay negative fluid balance compared to water in both groups. On five separate visits following an overnight fast, 12 young (Y, 23±3 yr, 7M/5F) and 12 older (O, 67±6 yr, 5M/7F) subjects consumed 1 L of distilled water, Gatorade (6% glu, 20 mmol/L Na+), Pedialyte (2.5% glu, 45 mmol/L Na+), Enterade (5 AA, 30 mmol/L Na+), or Enterade-AD (anti-diarrheal formulation; 8 AA, 60 mmol/L Na+) over a 30-minute period. Urine samples were collected before ingestion and at 0, 60, 120, 180, and 240 min post-ingestion. Beverage hydration index (BHI = 2 h cumulative urine output following water trial/ 2 h cumulative urine output following test beverage) was calculated for each beverage. Estimated glomerular filtration rate (eGFR) was lower in O compared to Y (71±3 vs. 94±6 ml∙min-1∙1.73 m-2, P<0.01). Older adults had prolonged urine excretion rates compared to young (P = 0.04). Water excretion rate was positively correlated with eGFR in older (R2 = 0.47, P = 0.01) but not young adults (R2 = 0.11, P = 0.32). In young subjects, BHI increased with beverage Na+ concentration and Enterade-AD had the highest BHI (Enterade-AD = 1.24 ± 0.10 vs. water = 1.00, P = 0.01). Older subjects had higher BHI compared to Y for all beverages and Enterade had the highest BHI (Enterade; 1.20 ± 0.13 vs. water; 1.00 ± 0, P < 0.01). Due to prolonged urine excretion rates, examining 4 h BHI may be more appropriate for older adults compared to 2 h BHI. After a bolus fluid load, healthy older adults exhibit a prolonged time course for urine excretion due to decreased eGFR. Increasing the beverage Na+ content progressively increases BHI in young adults independent of glucose or AA content. For older adults, the Enterade beverage with 5 AAs and moderate electrolyte content had the highest BHI and maintained hydration most effectively.