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Randomized Controlled Trial
. 2025 Jul 24;17(15):2418.
doi: 10.3390/nu17152418.

A Low-Sugar Flavored Beverage Improves Fluid Intake in Children During Exercise in the Heat

Sajjad Rezaei  1 , Rocio I Guerrero  2 , Parker Kooima  2 , Isabela E Kavoura  1 , Sai Tejaswari Gopalakrishnan  1 , Clarissa E Long  1 , Floris C Wardenaar  2 , Jason C Siegler  3 , Colleen X Muñoz  4 , Stavros A Kavouras  1
Affiliations
Randomized Controlled Trial

A Low-Sugar Flavored Beverage Improves Fluid Intake in Children During Exercise in the Heat

Sajjad Rezaei et al. Nutrients. .

Abstract

Objectives: This study examined the impact of a low-sugar flavored beverage on total fluid intake and hydration biomarkers during intermittent exercise in a hot environment among healthy children. Methods: Twenty-one children (11 girls, 8-10 y) completed a randomized, crossover study with two trials. Each trial involved three bouts of 10 min walking, 5 min rest, 10 min walking, and 35 min rest for a total of 3 h in a hot (29.9 ± 0.6 °C) and dry environment (26 ± 7% relative humidity). Walking intensity was 69 ± 7% of age-predicted maximum heart rate. Participants consumed either plain water (W) or a low-sugar flavored beverage (FB). Body weight, fluid intake, urine samples, and perceptual ratings were collected. Results: Total ad libitum fluid intake was significantly higher with the FB (946 ± 535 mL) than with W (531 ± 267 mL; p < 0.05). This difference was 128% higher for FB compared to W, with 19 out of the 21 children ingesting more fluids in FB versus W. Children rated the FB as more likable across all time points (p < 0.05). Net fluid balance was better with FB at 60, 70, 85, 135, and 145 min (p < 0.05), though not different at the 3 h mark. Urine volume was higher with FB (727 ± 291 mL) than with W (400 ± 293 mL; p < 0.05). Urine osmolality was significantly higher in the W trial at 120 and 180 min (p < 0.05). Conclusions: A flavored, low-sugar beverage enhanced ad libitum fluid intake and improved hydration markers compared to water during exercise in the heat, supporting its potential as a practical rehydration strategy for children.

Keywords: body fluid balance; dehydration; drinking; palatability; sweating.

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Conflict of interest statement

F.C.W. has received grants during the last 36 months from external partners that were not related to this project, including FEMA, Arizona Board of Regents, Pac-12 Health and Wellbeing Initiative, CSPDA, Standard Process Inc., The Kraft Heinz Company, Unilever Corporation, and Friesland Campina. J.C.S. has an active research grant from Unilever. C.X.M. served as a scientific consultant for The Kraft Heinz Company between 2021 and 2023, and since 2019, has received research funding from The Kraft Heinz Company, Niagara Cares, and the Drinking Water Research Foundation. S.A.K., during the last 36 months, has had active research grants from the National Science Foundation, USDA, The Kraft Heinz Company, Unilever, and Standard Process. During this time, he was a lead research aerospace physiologist at Luke Air Force Base and served as a member of the science advisory board for Hyduro Inc, Zico Rising, Trace Minerals, and Rockley Photonics. He has also provided scientific consultation to the American Beverage Association, Unilever, Pepsico, The Coca-Cola Company, and The Kraft Heinz Company. He is also the owner of Dr Hydration LLC.

Figures

Figure 1
Figure 1
Schematic representation of the protocol. The 3 h trial involved intermittent walking and rest periods in a hot, dry environment (29 °C, 26% RH). Body weight was assessed at 13 time points, and urine samples were collected at four time points to monitor hydration status. Participants had ad libitum access to either plain water or a flavored beverage throughout the protocol.
Figure 2
Figure 2
Cumulative fluid intake during the 3 h intermittent exercise in the heat. Participants consumed either a flavored beverage (FB) or plain water ad libitum. Values represent mean ± SE. * denotes statistically significant difference from Water for the same time point (p < 0.05).
Figure 3
Figure 3
Net fluid balance over time during intermittent exercise in the heat with ad libitum access to either a flavored beverage (FB) or plain water. Values represent mean ± SE. * denotes statistically significant difference from water for the same time point (p < 0.05).
Figure 4
Figure 4
Urine volume per collection (A) and cumulative urine volume (B) during the 3 h intermittent exercise in the heat with ad libitum access to either a flavored beverage (FB) or plain water. Values represent mean ± SE. * denotes statistically significant difference from Water for the same time point (p < 0.001).
Figure 5
Figure 5
Urine osmolality (A), osmotic excretion per collection (B), and cumulative osmotic excretion (C) during 3 h intermittent exercise in the heat with ad libitum access to either a flavored beverage (FB) or plain water. Values represent mean ± SE. * denotes statistically significant difference from Water for the same time point (p < 0.05).
Figure 6
Figure 6
Drink likeness perception was measured using a 175 mm visual analog scale during 3 h intermittent exercise in the heat with ad libitum access to either a flavored beverage (FB) or plain water. Values represent mean ± SE. * denotes statistically significant difference from Water for the same time point (p < 0.05).
See this image and copyright information in PMC

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