Overview
Caffeine is a central nervous system stimulant and ergogenic aid found in coffee, tea, chocolate, and dietary supplements. It enhances athletic performance by improving endurance, high-intensity efforts, resistance exercise, and cognitive-motor function in team and combat sports, likely through adenosine receptor antagonism, increased catecholamine release, and enhanced fat oxidation [1][2]. Caffeine also exhibits antioxidant properties, which may contribute to its protective effects against certain chronic diseases, though these benefits are dose- and source-dependent [4]. Acute supplementation improves exercise performance regardless of habitual caffeine intake, indicating that tolerance does not significantly blunt its ergogenic effects [2]. Caffeine ingestion before exercise can increase postexercise energy expenditure, particularly at higher doses (4.5 mg/kg), suggesting a role in energy metabolism [3]. While generally safe, adverse events—including cardiovascular and neurological symptoms—have been reported, especially with high-dose or energy drink formulations [5].
Dosage Guide
Therapeutic Doses
For treatment of specific conditions
Upper Intake Limit
Maximum safe daily intake
400 mg— For healthy adults; up to 400 mg/day considered safe by FDA. Higher doses linked to adverse events.
Special Forms
Alternative forms for specific needs
Common in supplements; more concentrated and consistent dosing
Faster absorption, useful for pre-competition or when rapid onset is desired
Clinical Notes
- High-dose caffeine (>400 mg/day) may cause insomnia, anxiety, tachycardia, and gastrointestinal distress.
- Energy drinks and concentrated supplements are associated with higher risk of adverse events including arrhythmias and hypertension [5].
- Individual response varies due to genetics (e.g., CYP1A2 polymorphism), habitual intake, and sex differences.
- Avoid in individuals with uncontrolled hypertension, cardiac arrhythmias, or anxiety disorders.
- Pregnant women should limit intake to <200 mg/day due to potential fetal risks.
Research
Caffeine improves performance in endurance, explosive efforts, resistance training, and team/combat sports; efficacy varies by form, with capsules, water, and gum being most effective.
Habitual caffeine consumption does not diminish the performance-enhancing effects of acute caffeine supplementation in endurance athletes.
Ingestion of 4.5 mg/kg caffeine before exercise significantly increases postexercise energy expenditure over 3 hours.
Caffeine has dose- and source-dependent antioxidant properties, contributing to potential health benefits beyond stimulation.
Caffeine-containing products, especially energy drinks, are associated with higher rates of adverse events including hospitalization and emergency department visits.
Caffeine chewing gum significantly enhances exercise performance, especially in trained individuals and for endurance and anaerobic efforts.
Caffeine improves sports performance in both men and women, though sex-specific responses may exist due to hormonal and metabolic differences.
Green tea consumption (a source of caffeine and catechins) significantly reduces systolic blood pressure by ~2 mmHg in randomized trials.
