Carbohydrate during exercise
Meta-analyses of more than 100 trials find carbohydrate during endurance exercise improves performance over placebo, with larger effects in longer events. A carbohydrate mouth rinse raised cycling power slightly. During lifting sessions over 45 minutes, total volume rose. Higher intake rates were linked to more nausea in races. Overdrinking any fluid was linked to hyponatremia.
Add to Bio HackChecked 2026-11-09
- Status
- Foods and beverages in the US.
- Also called
- sports drinks, energy gels, energy chews, carb drinks, glucose, maltodextrin, fructose, glucose-fructose, multiple transportable carbohydrates, hydrogel, carbohydrate mouth rinse, intra-workout carbs
- Taken for
- endurance, race performance, delaying fatigue, long workouts, lifting volume, recovery, hydration
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help4
- StrongShown to improve endurance performance over water in most studies, with larger gains in longer events and less trained people.
- StrongShown to raise cycling time-trial power slightly with a carbohydrate mouth rinse, without shortening completion time in cycling trials.
- ModerateShown to raise total resistance training volume, more in sessions over 45 minutes and after fasting 8 hours or more.
- ModerateShown to raise the burning of ingested carbohydrate with glucose-fructose over glucose alone in endurance athletes. Performance evidence comes from small trials.
What people take it for, and what was found
Shown to help4
Endurance performance
Shown to improve endurance performance over water in most studies, with larger gains in longer events and less trained people.
The numbers and sources
- Effect
- Across 61 performance studies (679 subjects), 82% found a significant benefit over water-only placebo, and the percentage gain grew with exercise duration [1]. A meta-analysis of 88 crossover studies found effects ranging from large gains of about 6% to moderate impairments of about 2%, depending on the supplement and protocol. Fructose above about 0.25 g per kg per hour possibly reduced the benefit [2]. A 2024 meta-analysis of 136 studies found a larger effect in time-to-exhaustion tests than time trials, in longer events and in less trained participants, with no moderation by dose or carbohydrate type [3].
- Population
- Trained and untrained adults in laboratory and field endurance tests [1][2][3].
- Sources
- [1], [2], [3]
- Caveats
- The three reviews disagree on whether dose and type matter [2][3]. Most trials are short crossovers in men. Time-to-exhaustion tests show larger effects than race-like time trials [3].
Mouth rinse in shorter efforts
Shown to raise cycling time-trial power slightly with a carbohydrate mouth rinse, without shortening completion time in cycling trials.
The numbers and sources
- Effect
- Across 13 studies (16 trials), a carbohydrate mouth rinse raised mean power output in cycling time trials (SMD 0.25, 95% CI 0.04 to 0.46) but did not shorten time to complete the trial (SMD -0.13, 95% CI -0.36 to 0.10) [4]. A 2026 meta-analysis of 90 crossover trials found small gains in distance covered (g 0.17, 95% CI 0.03 to 0.30), performance time (g -0.15, 95% CI -0.25 to -0.05), speed (g 0.17), workload (g 0.25, 95% CI 0.08 to 0.41) and maximum voluntary contraction (g 0.18). Muscular endurance, maximum power output and VO2max did not change [5].
- Population
- 175 cyclists for power and 151 for time [4]. Adults of any health and fitness status, mainly men [5].
- Sources
- [4], [5]
- Caveats
- Effects were small, with low heterogeneity [4][5]. The two reviews differ on completion time, which did not change in cycling time trials alone [4].
Resistance training volume
Shown to raise total resistance training volume, more in sessions over 45 minutes and after fasting 8 hours or more.
The numbers and sources
- Effect
- Across 21 crossover studies, carbohydrate raised total session volume over placebo (SMD 0.61). The effect was larger in sessions over 45 minutes (SMD 1.02) and after a fast of 8 hours or more (SMD 0.39). Carbohydrate dose did not moderate the effect [6].
- Population
- 226 healthy participants [6].
- Sources
- [6]
- Caveats
- One meta-analysis of short crossover studies. Volume is not the same as long-term strength or muscle gain, which was not tested.
Higher intake rates and glucose-fructose blends
Shown to raise the burning of ingested carbohydrate with glucose-fructose over glucose alone in endurance athletes. Performance evidence comes from small trials.
The numbers and sources
- Effect
- In 14 RCTs (125 endurance athletes), glucose-fructose raised exogenous carbohydrate oxidation by 0.27 g per minute over glucose alone, while glucose alone produced higher total carbohydrate oxidation (0.21 g per minute) [7]. In 11 cyclists riding 3 hours, 120 g per hour of a fructose-maltodextrin blend raised exogenous carbohydrate oxidation over 90 g per hour (1.51 versus 1.29 g per minute) without sparing more of the body's own carbohydrate. Performance was not tested [8]. In 11 runners, 90 g per hour of glucose-fructose as a hydrogel or a standard drink made a 5 km time trial 7.6% and 5.6% faster than placebo, and the hydrogel was 2.1% faster than the standard drink [9].
- Population
- Trained men [8][9]. Endurance athletes [7].
- Sources
- [7], [8], [9]
- Caveats
- The meta-analysis measured fuel oxidation, not performance [7]. The performance evidence is small trials. The 120 g per hour study was funded in part by TrainerRoad [8].
Doses studied
The systematic review linked longer events (more than 2 hours) with intake rates above 90 g per hour, using glucose and fructose together [1]. The 88-study meta-analysis inferred the largest benefit from a drink of about 3 to 10% carbohydrate providing about 0.7 g per kg per hour of glucose polymers and 0.2 g per kg per hour of fructose [2]. Recent trials compared 90 and 120 g per hour [8][9]. Athletes in endurance races took 6 to 136 g per hour [10].
Risks
Reported risks2
Gut symptoms
Limited evidence: higher carbohydrate intake rates in races went with nausea and flatulence, and also with faster Ironman times.
The numbers and sources
- Effect
- Among 221 endurance athletes in races, serious gut symptoms affected about 31% in Ironman races, 14% in half-Ironman and 4% in marathons and cycle races. Higher carbohydrate intake rates correlated with nausea and flatulence, and also with faster Ironman finishing times [10]. In runners, a standard glucose-fructose drink at 90 g per hour raised gut symptoms over placebo, while a hydrogel form did not [9].
- Population
- Triathletes, marathoners and cyclists in competition [10]; 11 trained runners [9].
- Sources
- [9], [10]
- Caveats
- The race study is observational and relied on post-race questionnaires. A history of gut problems was the strongest correlate of symptoms [10].
Hyponatremia from overdrinking
Limited evidence: 13% of 488 Boston Marathon runners finished with hyponatremia, linked to weight gain during the race, not to fluid type.
The numbers and sources
- Effect
- In 488 Boston Marathon runners, 13% finished with hyponatremia and 0.6% with critical hyponatremia. Weight gain during the race (OR 4.2, 95% CI 2.2 to 8.2) and finishing over 4 hours were associated with it. The composition of fluids ingested was not [11].
- Population
- Runners in the 2002 Boston Marathon [11].
- Sources
- [11]
- Caveats
- One race. Sports drinks and water were not compared in a trial.
Checked, no increase found1
Dental erosion
Limited evidence: erosion was not linked to sports drink use in 304 university athletes, in a 2002 survey.
The numbers and sources
- Effect
- In 304 university athletes, 91.8% used sports drinks and 36.5% had erosion. Erosion was not associated with sports drink use, quantity, frequency or years of use [12].
- Population
- Athletes at one US university [12].
- Sources
- [12]
- Caveats
- Cross-sectional, from 2002. Drink formulas and habits may have changed.
Claims tested and not found
- That sports drinks prevent hyponatremia better than water. Fluid composition was not associated with hyponatremia in marathon runners [11].
- That sports drinks erode athletes' teeth. Erosion was not associated with sports drink use in 304 athletes [12].
- That 120 g an hour spares more of the body's own carbohydrate than 90 g. Endogenous carbohydrate oxidation did not differ between the two rates [8].
- That a carbohydrate mouth rinse raises muscular endurance or VO2max. Neither changed across 90 crossover trials [5].
Sources
- Stellingwerff T, Cox GR. Systematic review: Carbohydrate supplementation on exercise performance or capacity of varying durations. Applied Physiology, Nutrition, and Metabolism. 2014. https://doi.org/10.1139/apnm-2014-0027
- Vandenbogaerde TJ, Hopkins WG. Effects of Acute Carbohydrate Supplementation on Endurance Performance. Sports Medicine. 2011. https://doi.org/10.2165/11590520-000000000-00000
- Ramos-Campo DJ, Clemente-Suárez VJ, Cupeiro R, et al. The ergogenic effects of acute carbohydrate feeding on endurance performance: a systematic review, meta-analysis and meta-regression. Critical Reviews in Food Science and Nutrition. 2023. https://doi.org/10.1080/10408398.2023.2233633
- Brietzke C, Franco-Alvarenga PE, Coelho-Júnior HJ, et al. Effects of Carbohydrate Mouth Rinse on Cycling Time Trial Performance: A Systematic Review and Meta-Analysis. Sports Medicine. 2018. https://doi.org/10.1007/s40279-018-1029-7
- Zalagkitis C, Kraniotaki A, Simitzis N, et al. Effects of Carbohydrate Mouth Rinse on Human Capacity and Performance: A Systematic Review and Meta-Analysis of 90 Controlled Trials. Nutrients. 2026. https://doi.org/10.3390/nu18183099
- King A, Helms E, Zinn C, et al. The Ergogenic Effects of Acute Carbohydrate Feeding on Resistance Exercise Performance: A Systematic Review and Meta-analysis. Sports Medicine. 2022. https://doi.org/10.1007/s40279-022-01716-w
- Dezfuli ZG, Rashedi MH, Naeini F, et al. Comparing the Effects of Glucose-Fructose versus Glucose on the Oxidation Rate: A Systematic Review and Meta-Analysis. Iranian Journal of Public Health. 2025. https://doi.org/10.18502/ijph.v54i4.18411
- Podlogar T, Bokal Š, Cirnski S, et al. Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g h-1 versus 90 g h-1 at different ratios. European Journal of Applied Physiology. 2022. https://doi.org/10.1007/s00421-022-05019-w
- Rowe JT, King RFGJ, King AJ, et al. Glucose and Fructose Hydrogel Enhances Running Performance, Exogenous Carbohydrate Oxidation, and Gastrointestinal Tolerance. Medicine & Science in Sports & Exercise. 2021. https://doi.org/10.1249/mss.0000000000002764
- Pfeiffer B, Stellingwerff T, Hodgson AB, et al. Nutritional Intake and Gastrointestinal Problems during Competitive Endurance Events. Medicine & Science in Sports & Exercise. 2012. https://doi.org/10.1249/mss.0b013e31822dc809
- Almond CS, Shin AY, Fortescue EB, et al. Hyponatremia among Runners in the Boston Marathon. New England Journal of Medicine. 2005. https://doi.org/10.1056/NEJMoa043901
- Mathew T, Casamassimo PS, Hayes JR. Relationship between Sports Drinks and Dental Erosion in 304 University Athletes in Columbus, Ohio, USA. Caries Research. 2002. https://doi.org/10.1159/000063927