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PubMed2026

Effects of continuous isomaltulose-containing gummy intake on interstitial glucose and salivary hormones during an 18-hole golf round: a randomized, double-blind controlled pilot study.

BACKGROUND: Golf is a prolonged, moderate-intensity sport requiring sustained physiological stability to manage cumulative stress and maintain performance. Although carbohydrate intake is commonly used to reduce fatigue, rapidly absorbed sugar-induced rapid blood glucose fluctuations may induce volatile arousal and latent metabolic stress. Isomaltulose, a slow-digesting disaccharide, provides a steadier glucose supply compared with sucrose. This exploratory pilot study examined the effects of isomaltulose intake on physiological stress markers, glycemic dynamics, and subjective responses during a competitive 18-hole golf round. METHODS: Twenty-three male collegiate golfers were randomized to either the isomaltulose group (ISO; n = 12) or the sucrose group (CON; n = 11) in a double-blind controlled trial. Participants consumed gummies containing isomaltulose or sucrose immediately after each hole (12.1 g carbohydrate per hole; total carbohydrate intake: 217.5 g). Primary outcomes were salivary stress markers [cortisol, testosterone, and dehydroepiandrosterone sulfate (DHEAS)] levels. Secondary outcomes included interstitial glucose concentration measured via continuous glucose monitoring, subjective assessments (i.e. sleepiness, relaxation, and concentration), and golf performance (18-hole score). Between-group comparisons at each time point were conducted using planned Welch's t-tests. RESULTS: No significant between-group differences were observed for 18-hole score (p = 0.38) or mean interstitial glucose concentration (p = 0.20). However, exploratory analyses revealed distinct hormonal variations; salivary DHEAS and testosterone levels were higher in the ISO group during the latter half of the round (p < 0.05), whereas both declined in the CON group. Regarding glycemic variability, the ISO group demonstrated a more stable glucose profile with a medium effect size for lower standard deviation (ISO: 14.7 ± 1.9 vs. CON: 16.7 ± 4.6 mg/dL; d = 0.58), although this difference was not significant. Conversely, subjective outcomes diverged; the CON group reported significantly greater subjective arousal (wakefulness and relaxation) (p < 0.01) relative to the ISO group. CONCLUSIONS: In conclusion, continuous intake of isomaltulose-containing gummies during an 18-hole golf round was associated with differences in selected physiological markers, including DHEAS and testosterone concentrations. However, these findings were not accompanied by improvements in objective golf performance outcomes compared with sucrose-containing gummies. Isomaltulose may influence glycemic dynamics and hormonal responses during prolonged golf play; however, the practical significance of these effects remains exploratory. Further studies with larger sample sizes and appropriate repeated-measures frameworks are needed to determine whether such physiological changes translate into meaningful performance or recovery benefits.

Humans↗

PubMed2026

Post-exercise rehydration: a randomized cross-over trial comparing a 100% fruit juice, a glucose-based sports drink, and water.

BACKGROUND: Previous studies indicate that sports drinks may improve rehydration, compared to water, an effect likely achieved by manufacturing sports drinks to contain carbohydrates and sodium. However, there is a growing preference for natural products and a "food first" approach to sports nutrition. Fruit juices naturally contain similar concentrations of carbohydrates to sports drinks, but fruit juices may produce a more stable blood glucose profile. Fruit juices also naturally contain electrolytes, particularly potassium, but their potential as effective rehydration alternatives to sports drinks, which have higher sodium concentrations, is not well understood. This study compared the rehydration efficacy and glucose responses following consumption of a 100% fruit juice (Raw Hydrate®; FRU), a glucose-based sports drink (SPO), and water (WAT) after exercise-induced hypohydration. Importantly, rehydration beverages were matched for water volume, rather than total volume, to ensure that any potential differences in water balance were not due to unequal water volumes between trials, a limitation affecting previous rehydration research. METHODS: After familiarization, 17 adults (age: 28 ± 8  years; BMI: 23.8 ± 2.9 kg/m2) completed three trials in a randomized cross-over design. The participants cycled in the heat (~35°C) to induce ~2% body mass loss (BML), then rehydrated over a 1 h period in a laboratory (~21°C) with a water volume equivalent to 150% of BML from either FRU, SPO, or WAT. This was followed by an additional 4 h of seated rest (5 h rehydration period), when blood glucose was measured (0, 0.25, 0.5, 0.75, 1, 1.5, and 2 h after beverage consumption), and all urine produced was collected. RESULTS: During the 5 h rehydration period, there was no effect of trial on total urine volume (FRU: 1266 ± 403 mL, SPO: 1338 ± 361 mL, WAT: 1394 ± 360 mL; P = 0.156) or water retention (FRU: 42 ± 12%, SPO: 37 ± 10%, WAT: 35 ± 11%; P = 0.059). The blood glucose area under the curve differed by trial (P < 0.001), with all beverages significantly different from each other (FRU: 10.12 ± 0.72 mmol/L/2h, SPO: 12.48 ± 1.34 mmol/L/2h, WAT: 7.90 ± 0.47 mmol/L/2h; P < 0.003). CONCLUSION: Rehydration efficacy was similar between all beverages, but each elicited a distinct glycemic response. For sports drink consumers seeking a natural alternative or implementing a "food first" nutritional strategy, switching to a 100% fruit juice will not compromise rehydration effectiveness, but may elicit a lower blood glucose response. Although, it should be noted that an additional three participants were withdrawn from the study because of gastrointestinal issues after consuming the 100% fruit juice. This was likely a product of the present study's design, where a large volume of 100% fruit juice (average ~2,300 mL) was consumed in a short period of time (1 h). Whilst this is a commonly used study design to robustly assess the rehydration efficacy of different beverages, future studies should distribute fluid intake over a longer duration, in order to improve ecological validity and reduce the risk of gastrointestinal issues.

Humans↗