This randomized trial tested the effects of a novel glycerol-electrolyte solution (GES) compared with placebo on fluid balance for 8 h. Twenty-five (12 female, 13 male) healthy, active adults (30 ± 7 y, 76.91 ± 13.27 kg) completed two trials in a randomized, counterbalanced order. After arriving at the laboratory euhydrated, participants emptied their bladder, then had baseline body mass measured. Participants consumed 1 L of GES (0.75% glycerol, 40 mmol/L sodium, 15 mmol/L potassium, 8 mmol/L magnesium, 5 mg calcium) or placebo (water with flavor and sweetness matched to GES) followed by urine collection and body mass measurements for 8 h. A two-way repeated-measures ANOVA (beverage × time) was conducted, followed by Tukey’s HSD test. Values are difference between beverages ± 95% CI. There was a significant effect of beverage, with fluid balance higher (0.15 ± 0.03%, p < 0.001) and urine output lower (-112 ± 23 g, p < 0.001) in the GES versus placebo trials across the 8-h observation period. There was also a beverage-by-time interaction effect: fluid balance was higher and urine output was lower 2 h (0.23 ± 0.14% and − 159 ± 98 g, p < 0.001), 3 h (0.19 ± 0.15% and − 144 ± 110 g, p = 0.001), and 4 h (0.18 ± 0.15% and − 137 ± 117 g, p < 0.01) with GES versus placebo. In summary, GES supported greater net fluid balance than placebo. The strongest pairwise differences occurred at 2–4 h, while the overall beverage effect was present across the full 8 h.
