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Gl7.5
Glycerol Research
Mostly mechanism / observationalHigh safety
12 peer-reviewed studies
What the evidence says
Mostly mechanism / observational
Most Glycerol studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from high-quality meta-analyses and randomised trials published 2001–2026 with a typical study size of 403 participants.
Based on 12 studies · 3 meta-analyses · 5 RCTs · 1,125 total participants
Confidence
High
What the studies found
2helped· 10 more without graded effect data
By outcome
Endurance & exercise performanceExtended time to exhaustion, especially in heat · 1-2 hours (acute use) · Hyperhydration; improves endurance in heat · 60-120 minutes
Mostly mechanism / observational12 studies
Safety profile
Too few graded studies2 studies
By the numbers
Pulled from 5 studies with measurable effects
Likely real effects
50%
across studies
People studied
1,125
typical study: 403 people
Strongest designs
8
3 pooled, 5 randomised
Showed benefit
100%
2/2 studies
Populations Studied
Athletes1
Combat sports athletes1
Healthy individuals1
Cyclists in esports and gravel disciplines1
Active research area
10 studies in the last 5 years · Latest meta-analysis: 2024
While no moderating effects were observed, lack of heterogeneity makes it difficult to generalise these findings.
McCubbin Aj et al. · Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme (2024)
Noticeable benefit
← WorseNo effectBetter →
Likely real
Meta-analysis determined overall effect size (Hedges' g), and meta-regression the influence of independent moderators (ambient temperature, hyperhydration agent, exercise mode, extent of hyperhydration).
A small-to-moderate improvement in time-to-exhaustion (TTE) (Hedges' g = 0.31, 95% CI: 0.13-0.50, p = 0.001) and time trial (TT) (g = 0.25, 95% CI: 0.002-0.51, p = 0.049) but not total work (TW) tasks (p = 0.120) was found following hyperhydration.
No effects were found for perceived exertion or thermal comfort.
2Performance enhancement in combat sportsMeta-AnalysisCited 14×2022
Caffeine is the only NEA that has shown strong evidence for performance enhancement in combat sports.
Vicente-Salar N et al. · Nutrients (2022)
In this regard, abilities including the number of attacks, reaction time, handgrip strength, power and TTE, among others, were improved.
Buffering supplements such as sodium bicarbonate, sodium citrate and beta-alanine may have a promising role in high and intermittent exertion during combat, but more studies are needed in grappling combat sports to confirm their efficacy during sustained isometric exertion.
Other NEAs, including creatine, beetroot juice or glycerol, need further investigation to strengthen the evidence for performance enhancement in combat sports.
In comparison with other plasma-volume expanding agents, glycerol hyperhydration has a very limited potential in increasing plasma volume and altering doping-relevant blood parameters.
Koehler K et al. · Drug testing and analysis (2013)
Barely noticeable benefit
← WorseNo effectBetter →
The meta-analysis revealed that the increase in plasma volume was 3.3% larger (95%-CI: 1.1-5.5%) after glycerol administration when compared to fluid only.
Reductions in haemoglobin were 0.2 g/dl (95%-CI: -0.3, 0.0) larger and there was no difference in the changes in haematocrit between glycerol and fluid administration (95%-CI: -0.7-0.8%).
Following a literature search, a total of seven studies was included and meta-analyses were performed separately for the effects on plasma volume (5 studies, total n = 54) and on haemoglobin (6 studies, n = 52) and haematocrit (6 studies, n = 52).
While performance supplements may enhance athletic performance when used alongside proper nutrition and scientific guidance, their effectiveness is not always consistent or assured.
Estevan Navarro P et al. · Nutrients (2025)
While performance supplements may enhance athletic performance when used alongside proper nutrition and scientific guidance, their effectiveness is not always consistent or assured.
This review highlights the urgent need to update regulatory frameworks, harmonize labeling standards, and promote ethical marketing to safeguard consumers and support sports and nutrition professionals.
However, no statistically significant effects were identified for the remaining supplements, whether administered individually or in combination.
Valiño-Marques A et al. · Nutrients (2024)
However, no statistically significant effects were identified for the remaining supplements, whether administered individually or in combination.
Thirty-six articles involving 701 participants were included in this review, examining supplementation with caffeine (n = 5), creatine (n = 2), sodium bicarbonate (n = 6), beta-alanine (n = 3), and nitrates (n = 8).
Additionally, supplemental combinations of caffeine and creatine (n = 3), caffeine and sodium bicarbonate (n = 3), caffeine and nitrates (n = 1), creatine and sodium bicarbonate (n = 1), and sodium bicarbonate and beta-alanine (n = 4) were analyzed.
6Nutrition strategies for cycling performanceSystematic Review2026
Finally, a number of supplements including caffeine, creatine, buffering agents, and hyperhydrating agents such as glycerol may enhance performance when used according to evidence-based protocols.
Whitfield J et al. · International journal of sport nutrition and exercise metabolism (2026)
We contextualize these responses by describing contemporary nutrition strategies and evidence-based practice adopted from other disciplines, along with practical application considering the distinct challenges presented by these new and emerging cycling disciplines.
Key issues for these disciplines include in race nutrition targeting the specific needs of the event, noting that the logistics of consuming food and drinks in gravel racing and Esports are different to other modalities such as road cycling.
Optimization of body mass is a shared concern particularly in Esports in which the requirement for a prerace "weigh-in" may lead to practices usually seen in weight division sports.
Adding Suc or Iso to Gly- and Na-contained beverages partially improves fluid balance but does not improve thermoregulatory responses and performance during moderate-intensity exercise in hot environments.
Otsuka J et al. · Medicine and science in sports and exercise (2025)
Compared with CON, beverages containing Gly and Na attenuated the total urine volume (all P < 0.001), and the addition of Iso (331 ± 84 g) further encouraged this response compared with Gly + Na and Gly + Na + Suc (429 ± 68 and 445 ± 133 g, respectively, both P ≤ 0.030).
Compared with CON, the plasma volume increased with Gly + Na + Suc during the first exercise bout (-2.2% ± 6.7% and 4.3% ± 5.4%, respectively, P = 0.048) and with Gly + Na + Iso during the TTE (-9.1% ± 4.4% and -4.1% ± 4.0%, respectively, P = 0.025).
No differences were found in TTE among the beverages ( P = 0.159).
Pre-exercise hyperhydration may improve exercise capacity during constant work rate exercise due to a reduced heart rate and core temperature, stemming from an acute increase in plasma volume.
Jardine WT et al. · Sports medicine (Auckland, N.Z.) (2023)
Two studies reported an improvement in time-trial performance (range 5.7-11.4%), three studies reported an improvement in total work completed (kJ) (range 4-5%) and five studies reported an increase in exercise capacity (range 14.3-26.2%).
Ten studies reported an increase in plasma volume (range 3.5-12.6%) compared with a control.
Pre-exercise hyperhydration may improve exercise capacity during constant work rate exercise due to a reduced heart rate and core temperature, stemming from an acute increase in plasma volume.
Fluid retention improved in G, SB and G + SB compared to CON, although there were no additive effects with G + SB compared to SB or G.
Patrick B et al. · PloS one (2026)
Borderline
Compared to CON, fluid retention was significantly higher with G + SB from 120-180 min, SB from 120-140 min, and G from 160-180 min (p < 0.05), and accumulated urine volume was significantly lower with G + SB from 100-180 min, SB from 120-180 min, and G from 140-180 min (p < 0.05).
Compared to G and CON, blood pH and blood bicarbonate concentration was significantly higher with G + SB and SB from 60-180 min (p < 0.05).
Fluid retention improved in G, SB and G + SB compared to CON, although there were no additive effects with G + SB compared to SB or G.
Glycerol- and sodium-induced hyperhydration improved hydration status without changing gastrointestinal symptoms prior to endurance exercise in warm conditions but did not improve half-marathon performance.
Jardine WT et al. · International journal of sports physiology and performance (2025)
HYP increased fluid retention compared with CON by 1189 mL, 95% CI 987-1391 (P < .001), and plasma volume by 9.0%, 95% CI 3.6-14.4 (P = .001).
However, there were no statistically significant differences in exercise performance, gastrointestinal symptoms, gastrointestinal temperature, and heart rate (P > .05 for mean values and at all time points).
Glycerol- and sodium-induced hyperhydration improved hydration status without changing gastrointestinal symptoms prior to endurance exercise in warm conditions but did not improve half-marathon performance.
Supplementation of beverages containing glycerol and sodium with isomaltulose but not sucrose enhances BHI from those of glycerol and sodium only under a resting state, likely due to the slow absorption of isomaltulose-derived monosaccharides (i.e., glucose and fructose).
Otsuka J et al. · Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme (2024)
The addition of isomaltulose increased BHI by ∼45% (3.43 ± 1.0 vs. 2.50 ± 0.7 for Gly + Na, P = 0.011) whereas sucrose did not (2.6 ± 0.6, P = 0.826).
Total urine volume was reduced in all beverages containing glycerol and sodium compared to CON (all P ≤ 0.002).
The PV expansion was earliest for Gly + Na (30 min), slower for Gly + Na + Suc (90 min), and slowest for Gly + Na + Iso (120 min) with a concomitant lag in the increase of blood glucose and sodium concentrations.