Nephrology · Medical Literature
Hydrating with a higher-fructose sport drink does not worsen acute kidney injury risk during simulated work-related heat stress.
Abstract
Fructose-containing soft drinks worsen acute kidney injury (AKI) risk during simulated work-related heat stress (WrHS), but the fructose content is comparatively lower in sport drinks. This study tested the hypothesis that consuming a higher-fructose sport drink exacerbates AKI risk compared with consuming a sucrose-sweetened sport drink during a 4-h WrHS simulation. In this block randomized, double-blind crossover study, 12 healthy adults (26 ± 7 yr; 6 women) completed two trials involving ingesting six 500 mL doses of a higher-fructose sport drink (55% fructose and 45% glucose; Fructose55) or a sucrose-sweetened sport drink (50% fructose and 50% glucose; Sucrose) before, during, and following a 4-h WrHS simulation that comprised three circuits of treadmill walking (10 min) and rowing (5 min) at five metabolic equivalents and 15 min of rest every hour. Drinks were matched for total carbohydrates, calories, and electrolytes and modestly matched for osmolality. Urine and blood samples were collected pre- and postexposure, at recovery, and 24 h post-visit. AKI risk was quantified as the product of urine insulin-like growth factor-binding protein 7 and urine tissue inhibitor of metalloproteinase-2 ([IGFBP7·TIMP-2]) normalized to specific gravity. Peak rectal temperature (Fructose55: 38.3 ± 0.7°C, Sucrose: 38.3 ± 0.7°C, P = 0.991) and percent change in body weight (Fructose55: -0.7 ± 1.0%, Sucrose: -0.9 ± 1.0%, P = 0.466) were not different between trials. Urinary [IGFBP7·TIMP-2] increased over time (P < 0.001) but did not differ between trials (peak change-Fructose55: 1.7 ± 1.6 (ng/mL)2/1,000, Sucrose: 1.6 ± 1.8 (ng/mL)2/1,000, P = 0.677). Consuming a higher-fructose-containing sport drink does not exacerbate AKI risk during WrHS when compared with a sucrose-sweetened equivalent.NEW & NOTEWORTHY This study tested whether drinking a sport drink with a higher proportion of fructose influences acute kidney injury (AKI) risk during simulated work-related heat stress. In a block randomized, double-blind crossover design, healthy adults consumed either a higher-fructose or sucrose-sweetened sport drink matched for calories, electrolytes, and carbohydrates. Despite increases in AKI biomarkers with heat stress, the type of sugar in the sport drink did not alter AKI risk, indicating that modest differences in fructose content do not meaningfully impact kidney stress.
Clinical relevance
Does consuming a higher-fructose sport drink (55% fructose / 45% glucose) exacerbate acute kidney injury risk compared with a sucrose-sweetened sport drink (50% fructose / 50% glucose) during a 4-hour simulated work-related heat stress scenario? __SNAPSHOT__ {"studyDesign":"Block randomized, double-blind, crossover trial","setting":"Laboratory-based environmental chamber simulation; institutional affiliation Indiana University School of Public Health – Bloomington (and collaborating institutions); country not explicitly stated but inferred as United States","sampleSize":"n = 12 (Fructose55 arm: n = 12; Sucrose arm: n = 12; crossover — same participants in both arms); 24-h follow-up sample n = 11","population":"Healthy adults; mean age 26 ± 7 years; 6 women (50%); no underlying kidney disease or heat-related illness reported; specific inclusion/exclusion criteria not fully reported in abstract","intervention":"Fructose55: six 500 mL doses of a higher-fructose sport drink (55% fructose / 45% glucose) administered before, during, and after a 4-hour work-related heat stress simulation (total volume 3,000 mL)","comparator":"Sucrose: six 500 mL doses of a sucrose-sweetened sport drink (50% fructose / 50% glucose); drinks were matched for total carbohydrates, calories, and electrolytes, and modestly matched for osmolality","primaryOutcome":"Acute kidney injury risk quantified as urinary [IGFBP7·TIMP-2] (product of insulin-like growth factor-binding protein 7 and tissue inhibitor of metalloproteinase-2, normalized to urine specific gravity) — a validated cell-cycle arrest biomarker panel","followUp":"Urine and blood samples collected at baseline (pre-exposure), immediately post-exposure, ~75 minutes post-exposure (recovery), and at 24 hours post-visit","fundingSource":"Not reported in the available abstract; one co-author (ZJS) has disclosed prior consultant fees from Otsuka Holdings Co., Ltd. per related publications from the same group"}
Key findings
The primary outcome, urinary [IGFBP7·TIMP-2] normalized to specific gravity, increased significantly over time across both trials (p < 0.001), indicating that the work-related heat stress simulation itself elevated AKI risk biomarkers regardless of beverage type. However, the between-trial comparison revealed no statistically significant difference in the peak change in [IGFBP7·TIMP-2] between the Fructose55 and Sucrose conditions (peak Δ: Fructose55 1.7 ± 1.6 (ng/mL)²/1,000 vs. Sucrose 1.6 ± 1.8 (ng/mL)²/1,000; p = 0.677). Physiological markers that could confound AKI biomarker interpretation were also similar between arms: peak rectal temperature (Fructose55: 38.3 ± 0.7°C vs. Sucrose: 38.3 ± 0.7°C; p = 0.991) and percent change in body weight (Fructose55: −0.7 ± 1.0% vs. Sucrose: −0.9 ± 1.0%; p = 0.466) were not different. Absolute effect size, relative risk reduction, NNT/NNH, confidence intervals for the primary outcome, and secondary biomarker-specific p-values (e.g., IGFBP7 and TIMP-2 individually) are not reported in the available abstract. No clinically important adverse events were reported in the abstract.
Practice implications
This study established that replacing a sucrose-sweetened sport drink with a higher-fructose sport drink (Fructose55, analogous to high-fructose corn syrup compositions used in commercial beverages) does not further increase urinary AKI biomarker [IGFBP7·TIMP-2] in healthy adults performing simulated occupational heat stress work. This finding is consistent with prior work from the same research group showing that sport drinks containing fructose-based sweeteners do not worsen AKI risk compared with sucrose- or non-caloric-sweetened alternatives during heat stress scenarios. Importantly, both beverage conditions were associated with a significant time-dependent rise in [IGFBP7·TIMP-2], confirming that the heat stress simulation itself — not beverage fructose composition — is the principal driver of AKI biomarker elevation. What this study did NOT establish: (1) whether either drink is protective against AKI compared with water or no fluid intake; (2) whether results generalize beyond healthy young adults to workers with pre-existing CKD, diabetes, or cardiovascular disease; (3) clinical AKI by KDIGO criteria, as only surrogate biomarkers were measured; (4) outcomes beyond 24 hours or across a full occupational shift (8 hours); (5) dose-response effects of varying fructose concentrations. The participant sample (n = 12, 50% women, mean age 26 years) is healthy and young, markedly unlike the occupational heat-exposed worker populations most at risk (older males, migrants, agricultural workers). Only the abstract was available for full appraisal; complete data on secondary endpoints, confidence intervals, and renal vascular Doppler outcomes were not extractable. __LIMITATIONS__ Very small sample size (n = 12) with insufficient statistical power to detect modest but clinically meaningful between-group differences; the study may be substantially underpowered, and a null finding cannot be equated with equivalence without formal non-inferiority analysis or power calculations for biomarker outcomes.,Surrogate biomarker endpoint only: urinary [IGFBP7·TIMP-2] is a validated predictor of AKI risk in critically ill patients but its clinical threshold and prognostic significance in the occupational heat stress context have not been established; no KDIGO-stage AKI was assessed.,Healthy young adult volunteers are not representative of the occupational populations at highest risk (e.g., older agricultural workers, those with CKD, hypertension, or diabetes); results may not be generalizable.,Crossover design with relatively short washout period details not reported in abstract; potential for carryover effects on biomarker trajectories cannot be excluded.,Osmolality was only 'modestly matched' between beverages, introducing a potential confound for urinary concentration and biomarker normalization.,The 4-hour simulation represents only half a typical occupational workday; longer exposure effects remain unknown.,Funding source and potential conflicts of interest not fully disclosed in the abstract; one author has a previously disclosed industry consulting relationship.,The study was powered and designed to detect differences between two active beverage conditions rather than against a water/placebo control, limiting conclusions about absolute safety of fructose-containing sport drinks.,Only the abstract was available for review; full statistical reporting (confidence intervals, secondary outcomes, renal vascular data) could not be independently verified. __BOTTOM_LINE_CATEGORY__ potentially_practice_informing __BOTTOM_LINE__ In 12 healthy young adults undergoing a 4-hour simulated occupational heat stress, a higher-fructose sport drink (55% fructose) did not worsen urinary AKI biomarker [IGFBP7·TIMP-2] compared with a sucrose-sweetened sport drink — suggesting fructose content at sport drink concentrations is not the key modifiable driver of heat stress-related AKI risk. Clinicians and occupational health practitioners should note that AKI biomarkers rose significantly in both conditions, underscoring that work-related heat stress itself poses a renal risk irrespective of beverage fructose composition. Given the small, healthy sample, surrogate endpoints, and single-center simulation design, these findings should be considered hypothesis-confirming and supportive, but not sufficient to change hydration guidelines for at-risk worker populations without replication in field settings and clinically relevant cohorts.