Glucose 150mg / Caffeine 30mg tablets

ObjectiveThis systematic review and meta-analysis evaluated the effects of caffeine (CAF) on high-intensity interval exercise (HIIE) performance and examined potential moderators.MethodsSeveral databases were searched for studies of CAF on HIIE performance. Pooled effects were calculated using Hedge's g (g) via a three-level random-effects meta-analysis. Subgroup analyses were performed based on sex, training status, CAF dose, CAF form, and interval type. A meta-regression analysis was conducted to investigate the potential moderating effect of the rest/work ratio on HIIE performance.ResultsTwenty studies were included (n = 320; 57 females). CAF significantly improved HIIE performance (g = 0.28, 95% CI = 0.14 to 0.43), concurrently elevating blood lactate (g = 0.50, 95% CI = 0.22 to 0.79) and glucose (g = 0.56, 95% CI = 0.17 to 0.96). Subgroup analyses demonstrated significant improvements across all sexes (g = 0.30-0.34), trained athletes (g = 0.44), CAF dose (low and moderate) (g = 0.28-0.33), CAF form (capsule and beverage) (g = 0.32-0.33), and HIIE protocol (repeated short sprints and short intervals) (g = 0.16-0.36), with no subgroup differences (all p > 0.05). The rest/work ratio was a significant moderator of HIIE performance (β2  = 0.003, p = 0.017).ConclusionCAF ingestion significantly enhances HIIE performance, with ergogenic benefits observed across both sexes and trained athletes. Effective ergogenic benefits can be achieved with a low dose (~3 mg/kg), administered as a capsule or beverage. Notably, meta-regression indicates that the rest/work ratio is a critical moderator of HIIE performance, with evidence of a nonlinear association.

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BackgroundRugby is a collision-based team sport requiring repeated high-intensity sprinting, technical execution, and physical contact under fatigue. Although caffeine is used as an ergogenic supplement, evidence from mixed team-sport populations may not be applicable to rugby. This systematic review evaluated the effects of acute caffeine supplementation on physical and sport-specific performance, perceptual responses, and physiological markers in rugby players.MethodsPubMed, Web of Science, Cochrane Library, Scopus, and Embase were searched from inception to May 1, 2026. Randomized placebo-controlled studies examining acute caffeine supplementation in rugby players were included in the quantitative synthesis, whereas observational studies related to sleep and recovery were narratively summarized. Standardized mean differences were calculated as Hedges' g with 95% confidence intervals. Three-level random-effects models accounted for dependent effect sizes. Methodological quality and risk of bias in randomized trials were assessed using the PEDro scale and RoB 2, respectively. Observational studies were assessed using the JBI checklist, and certainty of evidence was evaluated using GRADE.ResultsFifteen studies were included, and 13 randomized placebo-controlled trials contributed data to the meta-analysis. Acute caffeine supplementation was associated with small improvements in sprint performance (k = 11, Hedges' g = -0.41, 95% CI: -0.73 to -0.08, p = 0.02) and lower rating of perceived exertion (RPE) measured during or immediately after rugby-specific or resistance-exercise protocols (k = 9, Hedges' g = -0.40, 95% CI: -0.73 to -0.06, p = 0.02). A large positive effect was observed for passing accuracy (k = 9, Hedges' g = 1.65, 95% CI: 0.69 to 2.61, p = 0.004), but this finding showed high heterogeneity and potential small-study effects. No significant effects were found for jumping performance, strength performance, metabolic markers, or hormonal markers. Subgroup analyses did not identify moderating effects of rugby code, dose, form of administration, or competitive level. Observational evidence suggested possible sleep and recovery concerns following caffeine exposure.ConclusionIn rugby players, acute caffeine may improve sprint performance and passing accuracy while reducing RPE measured during or immediately after rugby-specific or resistance-exercise protocols. However, certainty of evidence ranged from low to very low, and findings should be interpreted cautiously.Systematic review registrationhttps://www.crd.york.ac.uk/prospero/, PROSPERO: CRD420261371265.

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Background and objectivesEvidence on the acute effects of caffeine in female team-sport athletes is limited. This study aimed to quantify the acute effects of caffeine on female team-sport athletes across physical performance, sport-specific performance, physiological responses, perceptual responses, and cognitive performance and determine moderators.MethodsPubMed and Web of Science were systematically searched for randomized, placebo-controlled crossover trials of acute, dose-defined caffeine in female team-sport athletes. Effect sizes were expressed as Hedges' g and synthesized within each domain using a three-level CHE model with CR2 cluster-robust variance estimation and Satterthwaite degrees of freedom; 95% confidence intervals and prediction intervals were reported. Risk of bias (RoB 2), methodological quality (PEDro), and certainty of evidence (GRADE) were assessed.ResultsTwenty-six studies were included, comprising 26 randomized, blind, placebo-controlled crossover trials. As a descriptive cross-domain summary, acute caffeine intake showed a small overall effect when all available domains were pooled (Hedges' g = 0.24, 95% CI 0.13 to 0.35); however, because these domains represent different constructs, domain-specific estimates were considered the primary interpretable findings. For physical performance, caffeine showed a small favorable effect (g = 0.32, 95% CI 0.22 to 0.42), with statistical evidence for repeated sprint ability (g = 0.43), agility or change in direction (g = 0.42), sprint or speed performance (g = 0.39), anaerobic power (g = 0.30), and jumping performance (g = 0.29). For sport-specific performance, the pooled estimate indicated a small favorable effect but did not reach conventional statistical significance (g = 0.36, 95% CI: -0.01 to 0.73). Exploratory sub-indicator analyses, each based on only a few studies, suggested possible favorable directions for sport-specific locomotion or running performance (g = 0.46) and throwing or ball-speed outcomes (g = 0.19), whereas evidence was insufficient for shooting or scoring accuracy. Physiological outcomes were direction-aligned to the value conventionally regarded as favourable for each indicator (i.e., lower heart rate, lactate, and glucose), so that positive values denote the conventionally favourable direction; because the domain aggregates indicators of differing clinical desirability, its pooled value is a descriptive summary only and showed no clear domain-level direction (g = -0.05, 95% CI -0.31 to 0.21). The heart rate submetric showed a statistically detectable difference (g = -0.30), indicating that caffeine increased heart rate, the expected pharmacological response to a stimulant rather than an adverse effect; there were no clear effects on blood lactate or blood glucose. Perceptual responses improved modestly (g = 0.42), largely through reduced rating of perceived exertion (g = 0.35). Cognitive performance, based on only four studies with low degrees of freedom and wide uncertainty, showed a nonsignificant direction (g = 0.37) with no clear evidence for reaction time or cognitive accuracy, and these data should not be interpreted as showing that caffeine improves cognitive performance in female team-sport athletes. Exploratory moderator analyses did not provide statistically reliable evidence of moderation by caffeine dose, timing of intake, formulation or source, sport type, competitive level, habitual caffeine intake, or blinding status.ConclusionsAvailable evidence most consistently supports small, outcome-specific benefits of acute caffeine for physical performance and reduced perceived exertion. Evidence for sport-specific skills and cognitive outcomes remained uncertain, based on few studies per outcome and not supporting a general benefit. Current data do not support dose-, timing-, formulation-, habitual-intake-, sport-, or population-stratified recommendations. Future trials should be adequately powered, prospectively report menstrual-cycle phase, hormonal-contraceptive use, habitual caffeine intake, and adverse symptoms, and verify the integrity of blinding.

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Catechins in green tea have been reported to enhance glucose tolerance and lipid metabolism. However, the influence of chronic intake timing on these outcomes in older adults has not been fully elucidated. In this randomized controlled trial, we investigated the effects of green tea intake at different timings on glucose and lipid metabolism in older adults. Forty-five participants aged ≥ 65 years were randomly assigned to morning (n = 15), day (n = 15), or evening (n = 15) group. Participants consumed green tea daily for 8 weeks at specified times (0600-1100, 1100-1600, and 1600-2100 h for the morning, day, and evening groups, respectively). Glucose metabolism, lipid metabolism, and body composition were evaluated before and after the intervention. Blood glucose level, glycated hemoglobin level, body weight, and fat mass decreased with green tea intervention, while muscle mass increased across all groups (all p Trial Registration: University Hospital Medical Information Network (UMIN): UMIN000058708.

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BackgroundUnfiltered Turkish coffee (UTC) is a traditional drink with high levels of bioactive compounds, but evidence of the associated specific physiological effects is inconclusive, and few studies have examined coffee in general. This pilot study aimed to investigate the short-term effects of daily UTC consumption on cardiovascular parameters, lipid profile, appetite-regulating hormones (leptin, ghrelin), glucose metabolism, inflammatory markers, and sleep quality in healthy young women.MethodsThis is a pilot randomized controlled trial that randomly assigned 40 healthy young women (aged 18-25 years) to intervention and control groups at a 1:1 ratio after 3 weeks of caffeine washout. The intervention group consumed three 40 mL cups of traditional-brewed UTC daily for 4 weeks, whereas the controls maintained abstinence from caffeine. The primary outcomes were cardiovascular (blood pressure, heart rate), lipid parameters, and the secondary ones were appetite hormones (leptin, ghrelin), glucose metabolism (markers), inflammatory biomarkers, and sleep quality, which were evaluated at baseline and at week 4.ResultsUTC consumption produced significant between-group differences (time × group interactions) compared to controls: systolic blood pressure (+3.0 mmHg; p = 0.025), heart rate (+10.6 bpm; p = 0.007), and insomnia severity scores (+4.05 points intervention vs. -1.00 points control; p ≤ 0.001), while significantly decreasing leptin levels (-0.04 ng/mL; p = 0.014). Significant changes in low-density lipoprotein (LDL) cholesterol were found (p = 0.002), although high-density lipoprotein (HDL) changes were no longer found significant on baseline correction (p = 0.385). Body composition parameters (body mass index (BMI), body fat mass, fat-free mass, skeletal muscle mass) remained unchanged throughout the intervention (all p > 0.05). No significant effects were observed for fasting blood glucose, glycated hemoglobin (HbA1c), inflammatory markers (C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α)), or ghrelin (all p > 0.05).ConclusionsFour weeks of UTC intake in this pilot trial were associated with variations in several cardiometabolic variables: interventions in systolic blood pressure (SBP) (+3.0 mmHg) and heart rate (HR) (+11.9 bpm) resulted in higher LDL levels, reduced leptin levels, and poor sleep quality, independent of body composition alterations. However, since the p-values are nominal and not multiplied by a correction, hypothesis-generating results require verification through properly powered studies. These exploratory findings should be considered by individuals with prior cardiovascular risk factors or sleep disorders when considering the intake of unfiltered coffee.Trial registrationThis trial was registered at ClinicalTrials.gov (NCT07133373, https://clinicaltrials.gov/study/NCT07133373). Retrospectively registered on 13 August 2025.

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