Research
Caffeine
135 peer-reviewed studies curated from PubMed and Semantic Scholar.
Studies
Sorted by quality and recency
The Caffeinated Brain Part 2: The Effect of Caffeine on Sleep-Related Electroencephalography (EEG)-A Systematic and Mechanistic Review.
This systematic and mechanistic review synthesizes human evidence on how caffeine affects sleep architecture and EEG markers of sleep homeostasis. Caffeine was found to suppress low-frequency NREM EEG activity and increase faster EEG activity, leading to a lighter, more aroused sleep profile. The review supports a model of adenosine receptor antagonism affecting sleep depth and recovery.
Comparative effects of respiratory stimulants in mechanically ventilated patients: a network meta-analysis of randomized controlled trials.
Network meta-analysis of 15 RCTs with 1,528 participants comparing ten respiratory stimulants in mechanically ventilated critically ill adults. No intervention significantly reduced hospital or ICU mortality, but some agents like nandrolone, growth hormone, and donepezil may help shorten ICU stay, reduce duration of mechanical ventilation, or improve weaning efficiency.
Caffeine and taurine: a systematic review and network meta-analysis of their individual and combined effects on physical capacity, cognitive function, and physiological markers.
Systematic review and network meta-analysis of caffeine and taurine, individually and combined, on physical capacity, cognitive function, and physiological markers. CAF+TAU showed positive effects on anaerobic capacity and reaction time compared to CAF or TAU alone. Caffeine reduced perceived exertion, while taurine tended to reduce blood lactate. No significant differences in heart rate were observed.
Energy Drinks as the Legal Cocaine? A Comparative Review of Cardiac Physiopathological and Histopathological Patterns.
This systematic review investigates the cardiac histopathological consequences of chronic energy drink consumption, highlighting significant cardiovascular risks such as QTc prolongation, arrhythmias, myocardial infarction, and hypertensive episodes. The review draws parallels between the effects of energy drinks and cocaine, emphasizing the cardiotoxic risk posed by excessive consumption.
Metabolite signatures associated with microRNA miR-143-3p serve as drivers of poor lung function trajectories in childhood asthma.
Meta-analysis of plasma metabolite principal components associated with lung function trajectories in children with asthma. The top metabolite component, including caffeine and other metabolites, was linked to better lung function and decreased neutrophil percentage. Associations with microRNA miR-143-3p and SNPs in target genes were also identified.
The Effectiveness of Caffeine in Reducing Constipation in Adults: A Systematic Review.
Systematic review assessing the effectiveness of caffeine in reducing constipation in adults. Eight studies were included, with mixed results: four studies suggested caffeine may reduce constipation, while four showed no improvement or an increase in constipation. Further rigorously designed RCTs are needed.
Effects of Coffee Supplementation on Homocysteine and Leptin Levels: A Systematic Review and Meta-analysis of Clinical Trials.
Systematic review and meta-analysis of clinical trials assessing the effects of coffee supplementation on homocysteine and leptin levels. Coffee administration significantly increases homocysteine levels but has no significant effect on leptin concentrations.
Preconception caffeine metabolites, caffeinated beverage intake, and fecundability.
The study examined associations between preconception serum caffeine metabolites, caffeinated beverage intake, and fecundability in 1228 women with a history of 1-2 pregnancy losses. Results showed that neither serum caffeine, paraxanthine, nor theobromine were associated with fecundability, and baseline intake of caffeinated beverages was not associated with fecundability.
Ergogenic Aids to Improve Physical Performance in Female Athletes: A Systematic Review with Meta-Analysis
Systematic review and meta-analysis of ergogenic aids in female athletes, evaluating performance in strength, sprint, and cardiovascular capacity. Caffeine improved jumping performance, isometric strength, and repetitions until failure. Caffeine and sodium phosphate improved sprint performance, while taurine, caffeine, and beta-alanine improved aerobic tests. No conclusive effects were found for beetroot juice, polyphenols, or creatine on aerobic performance.
Nutritional Ergogenic Aids in Combat Sports: A Systematic Review and Meta-Analysis.
Systematic review and meta-analysis of nutritional ergogenic aids in combat sports. Caffeine (5-10 mg/kg) showed strong evidence for enhancing performance by improving glycolytic energy production and tolerance to blood lactate levels, benefiting abilities like the number of attacks, reaction time, handgrip strength, power, and time to exhaustion.
Coffee and type 2 diabetes risk: Is the association mediated by adiponectin, leptin, c-reactive protein or Interleukin-6? A systematic review and meta-analysis.
This meta-analysis reviewed 69 cross-sectional and cohort studies to evaluate the association between coffee consumption and Type 2 Diabetes (T2D) risk. Coffee consumption was inversely associated with T2D risk, with higher adiponectin levels and lower leptin and CRP levels among coffee consumers, suggesting these as potential mediators.
Effect of Caffeine Intake on Postoperative Ileus: A Systematic Review and Meta-Analysis
Systematic review and meta-analysis of four studies with 341 patients examining the effect of coffee on postoperative ileus. Coffee administration significantly reduced the time to first bowel movement, first flatus, and tolerance of solid diet, with no complications attributed to coffee.
Impact of Acute Energy Drink Consumption on Blood Pressure Parameters: A Meta-analysis.
Meta-analysis of 15 studies evaluating the effects of acute energy drink consumption on blood pressure and heart rate. Acute consumption of caffeinated energy drinks significantly raised systolic and diastolic blood pressure, while heart rate changes were nonsignificant.
Coffee, tea, caffeine and risk of depression: A systematic review and dose-response meta-analysis of observational studies.
Systematic review and meta-analysis of observational studies on coffee, caffeine, and tea consumption and their association with depression risk. Higher coffee intake was associated with a reduced risk of depression, with a nonlinear J-shaped relation peaking at 400 mL/day. Tea showed a borderline nonsignificant association, while caffeine consumption showed a significant protective effect in prospective studies.
Caffeine metabolic phenotypes and hypertension risk: Urinary paraxanthine-to-caffeine ratio threshold and mediating pathways in NHANES.
Observational study using NHANES data to investigate the association between urinary paraxanthine-to-caffeine molar ratio (PMR) and hypertension risk. Faster caffeine metabolism (higher PMR) was associated with a reduced risk of hypertension, with SUA and WBC partially mediating this effect.
Short-Term Dietary Caffeine Intake for Alleviating Symptoms of Burning Mouth Syndrome: A Randomised Controlled Comparison With Alpha-Lipoic Acid.
This randomized controlled trial investigated the effects of daily supplementation of caffeine (120-150 mg) compared to alpha-lipoic acid (ALA) and a control group on symptoms of Burning Mouth Syndrome (BMS) in 118 patients. Both caffeine and ALA groups showed significant symptom relief compared to the control, with caffeine showing higher efficacy in Type I BMS patients.
Preoperative oral caffeine as prophylaxis against post-spinal hypotension in patients undergoing orthopedic lower limb surgery: A randomized, placebo-controlled, double-blinded study.
RCT investigating the efficacy of a 200 mg caffeine tablet as prophylaxis against post-spinal hypotension in patients undergoing lower limb orthopedic surgery. The caffeine group had significantly fewer hypotensive episodes and lower ephedrine requirements compared to the control group.
Applications and Benefits of Dietary Supplements in Taekwondo: A Systematic Review
Systematic review of 26 studies assessing the impact of 14 dietary supplements on taekwondo athletes. Strong evidence supports that acute ingestion of 3–5 mg/kg of caffeine enhances physical performance and psychological well-being. Other supplements like creatine, sodium bicarbonate, and beetroot require further investigation for efficacy.
Effects of supplementation with main coffee components including caffeine and/or chlorogenic acid on hepatic, metabolic, and inflammatory indices in patients with non-alcoholic fatty liver disease and type 2 diabetes: a randomized, double-blind, placebo-controlled, clinical trial.
RCT assessing the effects of 6 months of chlorogenic acid and/or caffeine supplementation on hepatic, metabolic, and inflammatory indices in patients with type 2 diabetes and NAFLD. Neither substance was superior to placebo in improving hepatic outcomes, except for lower total cholesterol in the caffeine group and higher insulin levels in the combined group.
Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children.
This systematic review evaluates the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and children. It concludes that up to 400 mg/day for adults and 300 mg/day for pregnant women is generally not associated with adverse effects. Limited data for children and adolescents suggest 2.5 mg/kg/day as an appropriate recommendation.
Acute impact of caffeinated alcoholic beverages on cognition: A systematic review.
Systematic review of 12 RCTs exploring cognitive disorders and subjective awareness associated with caffeinated alcoholic beverages (CAB) or alcohol with energy drinks (AED). Energy drinks may counteract some cognitive deficits of alcohol but increase impulsivity and risk of alcohol addiction.
Acute effects of caffeine-containing energy drinks on physical performance: a systematic review and meta-analysis.
Systematic review and meta-analysis of 34 studies evaluating the effects of caffeine-containing energy drinks on physical performance. ED ingestion improved performance in muscle strength, endurance, jumping, and sport-specific actions, with performance improvement associated with taurine dosage.
[Does coffee protect against type 2 diabetes?].
Meta-analysis synthesizing results of prospective studies on coffee consumption and type 2 diabetes risk. Most studies confirm a protective effect against type 2 diabetes, with a dose-response relationship and effects observed with both regular and decaffeinated coffee.
Comparative effects of caffeine and paraxanthine on rowing performance and sleep quality: a randomized crossover study
Randomized crossover study comparing the effects of caffeine and paraxanthine on rowing performance and sleep quality in 14 male university-level rowers. The combined caffeine and paraxanthine condition improved 2000-m performance and mean power output compared to placebo. Caffeine was associated with poorer sleep quality, while paraxanthine showed more favorable sleep outcomes.
Immune modulation in response to coffee intake: a pilot study.
Randomized pilot trial with 10 healthy volunteers comparing the effects of coffee brew, pure caffeine, and water on cytokine secretion. Both caffeine and coffee influenced immune homeostasis, with caffeine inducing a higher anti-inflammatory response compared to coffee.
Caffeine and Beetroot Juice Optimize 1,000-m Performance: Shapley Additive Explanations Analysis.
This study used a randomized crossover design to evaluate the effects of caffeine and beetroot juice on 1,000-m running performance in 20 healthy male participants. The combination of caffeine and beetroot juice significantly improved performance compared to placebo and beetroot juice alone. SHAP analysis identified key factors influencing performance, suggesting that tailored dietary supplement strategies can enhance performance and recovery.
Performance-enhancing effects of caffeine and L-Theanine among Iranian elite wrestlers: a focus on cognitive and specific physical performance.
This double-blind, placebo-controlled, crossover study investigated the effects of caffeine, L-theanine, and their combination on physical performance, cognitive function, and anxiety in 12 elite male wrestlers. The combination of caffeine and L-theanine improved strength, endurance, cognitive speed, and accuracy while reducing anxiety and caffeine-induced side effects compared to caffeine alone.
Acute Effects of Caffeine and Taurine Co-Ingestion on Time to Exhaustion and Thermoregulatory Responses to Cycling in the Heat.
Double-blind crossover study with 10 participants evaluating the effects of caffeine and taurine co-ingestion on time to exhaustion and thermoregulatory responses during cycling in the heat. No differences in time to exhaustion were observed, but increased ventilatory and metabolic demand was noted without ergogenic effects.
Acute Co-Ingestion of Caffeine and Sodium Bicarbonate on Muscular Endurance Performance.
This study evaluated the acute effects of co-ingesting caffeine and sodium bicarbonate on muscular endurance in 27 recreationally trained participants. Caffeine alone increased the number of repetitions, mean velocity, and power output in bench press and back squat exercises, but these effects were not observed when sodium bicarbonate was co-ingested.
The effect of caffeine dose on caffeine and paraxanthine changes in serum and saliva and CYP1A2 enzyme activity in athletes: a randomized placebo-controlled crossover trial
This randomized, double-blind, placebo-controlled crossover trial evaluated the effects of different doses of caffeine on caffeine and paraxanthine levels in serum and saliva, and CYP1A2 enzyme activity in 26 moderately-trained athletes. The study found dose- and time-dependent effects of caffeine supplementation on caffeine and paraxanthine levels, but no effect on CYP1A2 enzyme activity.
Comparative effects of caffeine, beta-alanine, and their combination on mechanical, physiological, and perceptual responses to upper-body superset resistance training.
This study used a randomized, triple-blinded, placebo-controlled crossover design to assess the acute effects of caffeine, beta-alanine, and their combination on mechanical, physiological, and perceptual responses during upper-body superset resistance training in 21 young resistance-trained males. The supplements had minimal effects on performance and physiological responses, with beta-alanine showing a slight decrease in the velocity of the last repetition compared to placebo.
Pharmacokinetic Profile of Caffeine and Its Two Main Metabolites in Dried Blood Spots After Five Different Oral Caffeine Administration Forms-A Randomized Crossover Study.
This randomized crossover study investigated the impact of five different caffeine formulations and administration routes on blood concentrations of caffeine and its metabolites in 16 healthy recreational athletes. The study found no significant differences in overall bioavailability, but the liquid caffeine formulation showed superior absorption in the first 5, 10, and 15 minutes compared to other forms.
The Effect of Creatine Nitrate and Caffeine Individually or Combined on Exercise Performance and Cognitive Function: A Randomized, Crossover, Double-Blind, Placebo-Controlled Trial.
This randomized, crossover, double-blind, placebo-controlled trial examined the effects of creatine nitrate and caffeine, alone and combined, on exercise performance and cognitive function in twelve resistance-trained male athletes. Co-ingestion of creatine nitrate and caffeine significantly enhanced cognitive function, particularly in cognitive interference tasks, without altering short-term exercise performance. No adverse events were reported.
Caffeine Gum Improves Reaction Time but Reduces Composure Versus Placebo During the Extra-Time Period of Simulated Soccer Match-Play in Male Semiprofessional Players.
This study investigated the effects of caffeine gum on perceptual-cognitive and physical performance during extra-time in simulated soccer match-play among semiprofessional male players. Caffeine gum improved reaction time but reduced composure compared to placebo, with no significant effects on neuromuscular or sprint performance.
Acute caffeine supplementation offsets the impairment in 10-km running performance following one night of partial sleep deprivation: a randomized controlled crossover trial.
RCT with 10 healthy recreational male runners testing caffeine supplementation's effect on 10-km running performance after partial sleep deprivation. Caffeine improved time trial performance by 7.7% following sleep deprivation and by 2.8% with normal sleep compared to placebo.
The Effect of Pre-Exercise Caffeine and Glucose Ingestion on Endurance Capacity in Hypoxia: A Double-Blind Crossover Trial.
Double-blind crossover trial with 8 healthy active young males examining the effect of pre-exercise caffeine and glucose supplementation on endurance performance in hypoxic conditions. Caffeine, glucose, and their combination significantly enhanced endurance capacity compared to placebo.
The Effect of Acute Pre-Workout Supplement Ingestion on Basketball-Specific Performance of Well-Trained Athletes.
Double-blind placebo-controlled study on the acute effects of a pre-workout supplement containing caffeine, creatine monohydrate, beta-alanine, citrulline malate, and BCAAs on basketball-specific performance. Significant improvements in counter-movement jump, agility, RAST average, minimum power, and fatigue index were observed in the supplement group, but no differences in sprinting, aerobic performance, and blood lactate concentrations.
Effect of single or combined caffeine and L-Theanine supplementation on shooting and cognitive performance in elite curling athletes: a double-blind, placebo-controlled study.
Double-blind, randomized controlled crossover study with 22 elite curling athletes examining the effects of caffeine and L-theanine supplementation on shooting and cognitive performance. The combined intake of caffeine and L-theanine significantly improved shooting scores and cognitive performance compared to placebo and single supplement intake.
Caffeine ingestion stimulates plasma carnitine clearance in humans.
A randomized placebo-controlled study with six healthy young adults investigated the effect of high-dose caffeine ingestion on plasma carnitine clearance during hypercarnitinemia. Caffeine ingestion stimulated plasma carnitine clearance, likely via increased Na/KATPase activity, suggesting a potential strategy for muscle carnitine loading to improve exercise performance.
Altered Caffeine Metabolism Is Associated With Recurrent Hypoglycemia in Type 2 Diabetes Mellitus: A UPLC-MS-Based Untargeted Metabolomics Study.
Case-control study of 80 T2DM patients investigating metabolic profiles associated with recurrent hypoglycemia. Caffeine and its metabolites were significantly lower in patients with recurrent hypoglycemia, suggesting caffeine metabolism abnormalities. Caffeine may serve as a biomarker and potential prevention strategy for recurrent hypoglycemia.
Effects of caffeine, methylliberine, and theacrine on vigilance, marksmanship, and hemodynamic responses in tactical personnel: a double-blind, randomized, placebo-controlled trial.
A double-blind, randomized, placebo-controlled trial tested the effects of caffeine, methylliberine, and theacrine on vigilance, marksmanship, and hemodynamic responses in tactical personnel. Both caffeine and the combination of caffeine, methylliberine, and theacrine improved reaction times during a vigilance task compared to placebo, though caffeine alone resulted in less favorable hemodynamic changes.
Acute Effect of Caffeine-Based Multi-Ingredient Supplement on Reactive Agility and Jump Height in Recreational Handball Players.
A randomized, double-blind, crossover study examined the acute effect of a caffeine-based multi-ingredient supplement on reactive agility and jump performance in 24 recreational handball male players. The supplement improved reactive agility but not jump height compared to placebo, with no significant difference between caffeine + guarana and the multi-ingredient supplement.
Effects of 3 mg/kg Body Mass of Caffeine on the Performance of Jiu-Jitsu Elite Athletes.
Double-blind, counterbalanced, crossover study on 22 traditional jiu-jitsu athletes examining the effects of 3 mg/kg body mass of caffeine. Caffeine increased performance in the Special Judo Fitness Test (SJFT), decreased fatigue perception, and increased power and endurance perception, but did not improve offensive and defensive technical actions during combat.
A double-blind, randomized, two-part, two-period crossover study to evaluate the pharmacokinetics of caffeine versus d9-caffeine in healthy subjects.
This study compares the pharmacokinetics of caffeine versus d9-caffeine in 20 healthy adults. Both substances were rapidly absorbed, with d9-caffeine showing higher plasma concentrations and lower exposure to active metabolites compared to caffeine. Both were well tolerated.
Does Single or Combined Caffeine and Taurine Supplementation Improve Athletic and Cognitive Performance without Affecting Fatigue Level in Elite Boxers? A Double-Blind, Placebo-Controlled Study.
Double-blind, randomized crossover study in 20 elite male boxers examining the effects of caffeine and taurine supplementation on physical and cognitive performance. Co-ingestion of caffeine and taurine improved peak power, balance, agility, and cognitive performance compared to placebo. The combination was more effective than single use of either supplement.
Acute Ketone Salts-Caffeine-Taurine-Leucine Supplementation but not Ketone Salts-Taurine-Leucine, Improves Endurance Cycling Performance.
RCT comparing the effects of ketone salts-caffeine-taurine-leucine (KCT) supplementation to caffeine-free ketone salts-taurine-leucine (KT) and an isoenergetic carbohydrate placebo (CHO-PLAC) on endurance cycling performance. KCT improved 20-km cycling time-trial performance and average power output compared to CHO-PLAC, with greater power output than both KT and CHO-PLAC.
Effect of different patterns of consumption of coffee and a cocoa-based product containing coffee on the nutrikinetics and urinary excretion of phenolic compounds.
A repeated-dose, randomized, crossover human intervention with 21 healthy volunteers studied the nutrikinetics and urinary excretion of phenolic compounds following different patterns of coffee and cocoa-based product containing coffee consumption. Significant differences in phenolic metabolite profiles were observed among treatments, with coffee hydroxycinnamates showing notable bioavailability.
Daily Caffeine Intake Induces Concentration-Dependent Medial Temporal Plasticity in Humans: A Multimodal Double-Blind Randomized Controlled Trial.
Double-blind, randomized, cross-over study examining the impact of 10-day caffeine intake (3×150 mg/day) on human gray matter volumes and cerebral blood flow in 20 habitual caffeine consumers compared to placebo. Caffeine intake resulted in significant reduction in gray matter volume in the medial temporal lobe, with larger reductions associated with higher caffeine concentrations. No link was found between sleep depth and changes in brain morphology.
Pain Bloc-R Alleviates Unresolved, Non-Pathological Aches and Discomfort in Healthy Adults-A Randomized, Double-Blind, Placebo-Controlled, Crossover Study.
This randomized, double-blind, placebo-controlled, crossover study compared the effects of Pain Bloc-R, acetaminophen, and placebo on unresolved aches and discomfort in 27 healthy adults. Pain Bloc-R significantly reduced 'pain at its worst' scores and improved 'pain at its least' scores compared to acetaminophen, with significant reductions in pain severity and interference in male participants ≤45 years.
Short term effects of coffee components consumption on gut microbiota in patients with non-alcoholic fatty liver and diabetes: A pilot randomized placebo-controlled, clinical trial
Pilot RCT of 26 patients with diabetes and NAFLD assessing the effects of caffeine and chlorogenic acid on gut microbiota and metabolic disturbances. The CFCA group showed significant weight reduction compared to other groups, with a non-significant increase in gut Bifidobacteria.
Energy Drink Doses of Caffeine and Taurine Have a Null or Negative Effect on Sprint Performance.
This study investigated the effects of caffeine and taurine coingestion on repeat-sprint cycling performance in 11 male subjects. The caffeine and taurine supplement did not improve performance and seemed to induce greater fatigue within selected sprints, particularly at the end of the trial, along with increased heart rate and glycolytic metabolic by-products.
Cognitive enhancement effects of stimulants: a randomized controlled trial testing methylphenidate, modafinil, and caffeine.
RCT testing the cognitive enhancement effects of caffeine, methylphenidate, and modafinil in healthy male participants. Caffeine showed a positive effect on sustained attention, while methylphenidate improved self-reported fatigue and declarative memory. Modafinil showed no significant effects.
Effects of Coffee Components on Muscle Glycogen Recovery: A Systematic Review.
Systematic review analyzing the effects of coffee and its components on muscle glycogen metabolism. Caffeine was shown to increase glucose levels and glycogen resynthesis rates in humans and rats. Cafestol and caffeic acid increased insulin secretion and glucose uptake, while chlorogenic acid showed no effect. Coffee components generally had a neutral or positive role in glucose and muscle glycogen metabolism.
Evidence-based treatment of neurogenic orthostatic hypotension and related symptoms.
Systematic review of therapeutic options for neurogenic orthostatic hypotension and related symptoms. Strong recommendations for midodrine and droxidopa, with caffeine among alternative agents with weak recommendation due to low quality of evidence.
Effects of coffee and caffeine anhydrous on strength and sprint performance.
RCT comparing the effects of acute coffee and caffeine anhydrous intake on strength and sprint performance in 54 resistance-trained males. Coffee improved leg press 1RM more than caffeine anhydrous, but neither improved strength outcomes more than placebo. Both coffee and caffeine anhydrous attenuated sprint power reductions similarly.
Ingesting a preworkout supplement containing caffeine, creatine, β-alanine, amino acids, and B vitamins for 28 days is both safe and efficacious in recreationally active men.
Double-blind, placebo-controlled study on the safety and efficacy of a preworkout supplement containing caffeine, creatine, beta-alanine, amino acids, and B vitamins in recreationally active men over 28 days. Significant improvements in body composition and performance metrics were observed, with no adverse effects on renal and hepatic markers, heart rate, or blood pressure.
Serum metabolite/caffeine ratios as a test for liver function.
The study tested the usefulness of metabolite/caffeine ratios for evaluating hepatic dysfunction. Subjects with liver cirrhosis, chronic hepatitis, and healthy volunteers were given 300 mg caffeine. Pharmacokinetic parameters and metabolite/caffeine ratios were calculated, showing decreased caffeine elimination in cirrhotic patients compared to healthy volunteers.
The effects of a thermogenic supplement on metabolic and hemodynamic variables and subjective mood states.
RCT with 23 female participants examining the effects of a thermogenic supplement on metabolic rate, hemodynamic responses, and mood states. The supplement increased resting energy expenditure and reduced fatigue without adverse hemodynamic effects.
Caffeine, Paraxanthine, Theophylline, and Theobromine Content in Human Milk
Observational study assessing caffeine and its metabolites in breast milk from 100 women in Poland. Higher caffeine levels were found in milk from women living in cities, with secondary education, aged 34–43, and in later lactation periods. A positive correlation was found between caffeine consumption and its level in milk.
Evaluation of a six-probe cocktail (caffeine, tolbutamide, omeprazole, dextromethorphan, midazolam, and digoxin) approach to estimate hepatic drug detoxification capability and dosage requirements after a single oral dosing in healthy Chinese volunteers.
This phase I clinical study evaluated a 6-probe cocktail including caffeine to assess drug metabolizing enzyme activity in 20 healthy Chinese volunteers. The study found the cocktail to be safe and effective for assessing drug metabolism, with genetic variations correlating with phenotypic status.
Quantification of Caffeine Interactions in Choline Chloride Natural Deep Eutectic Solvents: Solubility Measurements and COSMO-RS-DARE Interpretation
The study measures the solubility of caffeine in choline chloride natural deep eutectic solvents (ccNADES) with various polyalcohols. It uses COSMO-RS-DARE to assess intermolecular interactions and optimize caffeine solubility, providing methodological insights into solubility computations.
Energy drinks and population health: consumption pattern and adverse effects among Saudi population
Cross-sectional study of 783 Saudi individuals assessing consumption patterns and adverse effects of caffeine-containing energy drinks. Consumers reported using EDs for fatigue reduction, increased alertness, and focus, but also experienced adverse effects like diuresis, palpitations, and insomnia. An inverse association was found between knowledge of EDs and consumption rate.
Energy Drinks Induce Acute Cardiovascular and Metabolic Changes Pointing to Potential Risks for Young Adults: A Randomized Controlled Trial.
This randomized crossover trial examined the cardiovascular and metabolic effects of energy drinks (EDs) and their components in 38 young adults. A single high-volume intake of ED caused adverse changes in blood pressure, QTc interval, and insulin sensitivity, with caffeine contributing to increased blood pressure.
Identification of the caffeine to trimethyluric acid ratio as a dietary biomarker to characterise variability in cytochrome P450 3A activity.
The study evaluated the caffeine to trimethyluric acid ratio as a biomarker for variability in CYP3A activity in 28 healthy males. Correlations between midazolam clearance and caffeine/TMU ratio were strong both pre- and post-rifampicin dosing, suggesting the ratio may be a useful tool for assessing CYP3A activity variability.
Effects of acute caffeine, theanine and tyrosine supplementation on mental and physical performance in athletes.
RCT with 20 male collegiate athletes testing a supplement containing caffeine, theanine, and tyrosine versus placebo. The supplement improved movement accuracy and dynamic performance measures, suggesting potential ergogenic value for sports requiring rapid and accurate movements.
Acute Ingestion of a Mixed Flavonoid and Caffeine Supplement Increases Energy Expenditure and Fat Oxidation in Adult Women: A Randomized, Crossover Clinical Trial.
This randomized, double-blinded, crossover study measured the acute effect of a mixed flavonoid-caffeine supplement on energy expenditure and fat oxidation in premenopausal women. The supplement increased energy expenditure compared to placebo, with a small effect on fat oxidation.
Postprandial glycaemic and lipaemic responses to chronic coffee consumption may be modulated by CYP1A2 polymorphisms.
RCT investigating the effects of regular coffee intake on glucose and lipid metabolism in coffee-naïve individuals, analyzed by CYP1A2 genotype. No significant differences were found between groups overall, but genotype-specific differences were observed in glucose and NEFA levels.
Cognitive Performance Enhancement Induced by Caffeine, Carbohydrate and Guarana Mouth Rinsing during Submaximal Exercise.
RCT with 24 participants investigating the effects of mouth rinsing with caffeine, carbohydrate, and guarana on cognitive performance during 40-min submaximal exercise. Caffeine mouth rinsing likely improved cognitive control, while carbohydrate and guarana improved temporal performance. Carbohydrate also decreased subjective perception of effort.
Acute effects of energy drinks in medical students.
RCT involving 80 healthy medical students to assess the acute effects of energy drinks containing caffeine on cardiovascular parameters, stress levels, and working memory. Significant increases in systolic blood pressure and heart rate were observed in some groups, while cortisol levels and cognitive performance varied across groups.
Twelve weeks supplementation with an extended-release caffeine and ATP-enhancing supplement may improve body composition without affecting hematology in resistance-trained men.
RCT of 21 resistance-trained men supplementing with extended-release caffeine and ancient peat and apple extracts for 12 weeks. The supplement group showed increased muscle cross-sectional area and thickness compared to placebo, suggesting enhanced muscle hypertrophy without affecting blood chemistry.
Effects of a Novel Fixed Combination of Nutraceuticals on Serum Uric Acid Concentrations and the Lipid Profile in Asymptomatic Hyperuricemic Patients : Results from the PICONZ-UA Study.
Double-blind, placebo-controlled RCT assessing the effects of ZinutriK (a combination of kampferol, baicalin, caffeine, and rutin) on serum uric acid levels and lipid profile in 16 asymptomatic hyperuricemic patients. ZinutriK reduced serum uric acid, decreased LDL cholesterol, increased HDL cholesterol, and improved the Framingham risk score over 4 weeks without side effects.
The Safety, Pharmacokinetics, and Nervous System Effects of Two Natural Sources of Caffeine in Healthy Adult Males.
Double-blind crossover clinical trial with 12 adult males comparing 200 mg caffeine from green coffee extract, guayusa leaf extract, and a synthetic control. No significant changes in blood pressure or heart rate were observed. Guayusa extract showed a lower increase in epinephrine compared to control, while green coffee extract had a similar effect to control.
The Effect of Caffeine on Repeat-High-Intensity-Effort Performance in Rugby League Players.
Double-blind, placebo-controlled, crossover RCT with 11 semiprofessional rugby league players examining the effect of 300 mg caffeine on repeat-high-intensity-effort performance. Caffeine ingestion resulted in a 1.0% faster total time for 20-m sprints compared to placebo, with improvements more pronounced in early test stages.
A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood.
A double-blind, placebo-controlled crossover study examined the effects of caffeine and L-theanine on cerebral blood flow, cognition, and mood in 24 participants. Caffeine improved attention and mood but reduced oxygenated haemoglobin. Combining L-theanine with caffeine eliminated caffeine's vasoconstrictive and behavioural effects, with no positive impact on behaviour at tested levels.
The Effect of Caffeine Ingestion during Evening Exercise on Subsequent Sleep Quality in Females.
RCT with 10 females on monophasic oral contraceptives examining the effect of evening caffeine ingestion on sleep quality. Caffeine ingestion impaired sleep latency and quality, with no differences in feelings upon awakening.
Effects of energy drink major bioactive compounds on the performance of young adults in fitness and cognitive tests: a randomized controlled trial
This randomized controlled trial tested the effects of caffeine and taurine, individually and in combination, on physical and cognitive performance in 14 male soldiers. The study found no statistically significant differences in performance measures between the treatments and placebo, and no adverse effects were reported.
Effect of post-exercise caffeine and green coffee bean extract consumption on blood glucose and insulin concentrations.
RCT investigating the effects of caffeine and green coffee bean extract on blood glucose and insulin concentrations during a post-exercise oral glucose tolerance test in 10 male cyclists. No significant differences in blood glucose and insulin levels were found between the caffeine, green coffee bean extract, and placebo trials.
Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task.
RCT with 27 participants assessing the effects of caffeine and theanine on vigilance during a sustained attention task. Caffeine and theanine reduced error rates compared to placebo, but the combination did not provide additional benefits. Caffeine reduced alpha-band oscillatory activity, while theanine did not affect it.
Ingesting a pre-workout supplement containing caffeine, B-vitamins, amino acids, creatine, and beta-alanine before exercise delays fatigue while improving reaction time and muscular endurance
RCT with 12 recreationally-trained males testing the effects of a pre-workout supplement containing caffeine, B-vitamins, amino acids, creatine, and beta-alanine. The supplement improved lower body muscular endurance, agility choice reaction performance, perceived energy, and reduced subjective fatigue.
Evaluation of the efficacy of a topical cosmetic slimming product combining tetrahydroxypropyl ethylenediamine, caffeine, carnitine, forskolin and retinol, In vitro, ex vivo and in vivo studies.
The study evaluated a topical cosmetic slimming product containing caffeine, carnitine, forskolin, and retinol. A double-blind, randomized, placebo-controlled clinical study on 78 women showed significant reductions in body circumference and improvements in skin aspect after 12 weeks of application.
Effects of coffee consumption on subclinical inflammation and other risk factors for type 2 diabetes: a clinical trial.
Clinical trial investigating the effects of coffee consumption on biomarkers of inflammation, oxidative stress, and lipid metabolism in 47 habitual coffee drinkers. Coffee consumption increased serum caffeine, chlorogenic acid, and caffeic acid metabolites, improved HDL cholesterol levels, and reduced subclinical inflammation markers, but showed no changes in glucose metabolism.
Positive effects of Red Bull® Energy Drink on driving performance during prolonged driving.
Double-blind placebo-controlled crossover study with 24 healthy volunteers examining the effects of Red Bull Energy Drink on driving performance. Red Bull significantly improved driving performance, reduced sleepiness, and enhanced subjective driving quality during prolonged driving.
Acute effects of a caffeine-containing supplement on bench press and leg extension strength and time to exhaustion during cycle ergometry.
The study examined the acute effects of a caffeine-containing supplement on 1RM bench press and leg extension strength, as well as time to exhaustion during cycle ergometry in 21 untrained men. The results indicated no effect of the supplement on strength or time to exhaustion, suggesting it is not an effective ergogenic aid in untrained individuals.
Caffeine and paraxanthine HPLC assay for CYP1A2 phenotype assessment using saliva and plasma.
The study developed a reverse-phased C(18) HPLC assay to measure caffeine and paraxanthine concentrations in saliva and plasma, using ethyl acetate liquid-liquid extraction. The assay was tested on two healthy volunteers who received a single 100 mg oral dose of caffeine, demonstrating its utility in assessing CYP1A2 activity.
Improved cycling time-trial performance after ingestion of a caffeine energy drink.
Double-blind, randomized, crossover study with 12 trained cyclists investigating the effects of Red Bull Energy Drink on endurance performance. Consuming the energy drink improved cycling time-trial performance compared to placebo, without increasing perceived exertion.
Metabolic and hormonal effects of caffeine: randomized, double-blind, placebo-controlled crossover trial.
A double-blind, randomized, placebo-controlled crossover study evaluated the effect of 200 mg caffeine taken twice daily for 7 days on glucose metabolism and hormone levels in 16 healthy adults. Caffeine intake significantly increased insulin levels and reduced insulin sensitivity, with no differences observed in glucose, DHEA, androstenedione, and melatonin levels.
The effect of caffeine, green tea and tyrosine on thermogenesis and energy intake.
RCT with 12 healthy men testing the effects of caffeine, green tea extract, and tyrosine on thermogenesis and energy intake. Caffeine increased thermogenesis by 6% above baseline, while green tea extract and tyrosine did not show significant effects. Energy intake was slightly reduced with all treatments compared to placebo.
Diuretic potential of energy drinks.
Cross-over study with 12 healthy male volunteers examining diuretic effects of caffeine and taurine in energy drinks. Caffeine significantly increased urinary output and natriuresis, while taurine showed no significant effects. The diuretic effects of the energy drink were largely attributed to caffeine.
Electrocardiographic effects of an Ephedra-Free, multicomponent weight-loss supplement in healthy volunteers.
Randomized, double-blind, placebo-controlled, crossover study of Metabolife Ephedra Free, a weight-loss supplement containing caffeine, green tea, garcinia cambogia, and yerba mate, in 20 healthy volunteers. No significant differences in the QTc interval or other ECG variables were observed between the supplement and placebo groups over a 5-hour period.
The effect of an herbal supplement containing black tea and caffeine on metabolic parameters in humans.
A double-blind, placebo-controlled, crossover study on 16 healthy subjects tested an herbal supplement containing black tea and caffeine for thermogenesis. The supplement significantly increased resting metabolic rate and systolic blood pressure compared to placebo.
Population pharmacokinetics of caffeine and its metabolites theobromine, paraxanthine and theophylline after inhalation in combination with diacetylmorphine.
Study of the population pharmacokinetics of caffeine and its metabolites after inhalation in combination with diacetylmorphine in 10 individuals. Caffeine was rapidly absorbed, with a bioavailability of approximately 60%. The pharmacokinetics were described by a linear multi-compartment model.
Salivary caffeine metabolic ratio in alcohol-dependent subjects.
The study assessed caffeine clearance and salivary paraxanthine/caffeine ratio in alcohol-dependent subjects compared to healthy controls. It found that caffeine clearance and PX/CA ratio were altered in alcohol-dependent patients with abnormal liver function. The study also evaluated the effect of NAT2 genotypes on PX/CA ratio, finding no significant impact.
Effect of caffeine-containing versus decaffeinated coffee on serum clozapine concentrations in hospitalised patients.
A randomised placebo-controlled cross-over study with 12 hospitalised clozapine-using patients examined the effect of caffeine-containing versus decaffeinated coffee on serum clozapine concentrations. Caffeine-containing coffee increased the mean serum trough concentration of clozapine by 26% in compliant patients, though this was not statistically significant. The study suggests that caffeine may inhibit clozapine metabolism via CYP1A2 enzyme inhibition.
Use of oral contraceptives blunts the calciuric effect of caffeine in young adult women.
This study evaluated the influence of oral contraceptive use on the urinary excretion of minerals and caffeine metabolites in response to a high caffeine dose in young adult women. The study found that oral contraceptive users had a significantly lower net increase in urinary excretion of calcium and other minerals compared to non-users, suggesting that oral contraceptives may limit the renal effect of caffeine on mineral excretion.
Two novel methods for the determination of CYP1A2 activity using the paraxanthine/caffeine ratio.
The study compared two novel methods for estimating CYP1A2 activity using the paraxanthine/caffeine ratio in eight healthy volunteers. The methods showed good predictive performance for caffeine clearance without requiring long periods of caffeine abstinence.
Influence of the urine flow rate on some caffeine metabolite ratios used to assess CYP1A2 activity.
The study assessed the influence of urine flow rate on caffeine metabolite ratios used to measure CYP1A2 activity. It involved 27 subjects undergoing caffeine tests before and after 14 days of omeprazole treatment. Results showed that certain metabolite ratios were enhanced after treatment, with changes inversely associated with urine flow rate. The study highlights the need for controlling liquid intake in studies using caffeine metabolite ratios to assess CYP1A2 activity.
Efficacy of a 'functional energy drink' in counteracting driver sleepiness.
RCT investigating the effectiveness of a functional energy drink containing caffeine, taurine, and glucuronolactone in reducing driver sleepiness. The drink significantly reduced sleep-related driving incidents and subjective sleepiness for the first 90 minutes of driving after sleep restriction.
Urinary biomarkers for assessing dietary exposure to caffeine.
The study investigates the use of urinary metabolites as biomarkers for estimating dietary caffeine intake. It examines inter-individual differences in caffeine metabolism and the effect of phenotype on biomarker interpretation, using data from up to 20 human volunteers. The study identifies three metabolites as potential biomarkers for caffeine intake.
Urinary caffeine after coffee consumption and heat dehydration.
This study evaluated the effect of heat-induced dehydration on urinary caffeine excretion after coffee consumption in ten healthy males. Dehydration reduced urine flow and delayed peak urinary caffeine concentration, but did not lead to higher caffeine concentration in urine due to elimination in sweat.
The effects of acute falciparum malaria on the disposition of caffeine and the comparison of saliva and plasma-derived pharmacokinetic parameters in adult Nigerians.
The study evaluated the pharmacokinetics of caffeine and its metabolites in ten healthy Nigerians and ten Nigerians with acute uncomplicated Plasmodium falciparum malaria. The study found significant changes in the disposition of caffeine metabolites in malaria patients compared to healthy controls. Saliva analysis was found to be a useful non-invasive method for monitoring caffeine kinetics.