Two capsules. The same ~5 mg/kg of caffeine. Only one of them produced a statistically significant jump in peak power. A new crossover trial in Sport Sciences for Health put guarana head to head with anhydrous caffeine, and the result is more interesting, and more nuanced, than the headline suggests.
What the Study Did
Researchers led by da Rocha Rodrigues and colleagues recruited 18 physically active young men (average age 21.8 ± 2.5 years). The design was randomized, double-blind, placebo-controlled and crossover, so every participant tried all three conditions:
- Guarana (Paullinia cupana) capsules
- Anhydrous caffeine capsules
- Placebo capsules
The key detail is that the two active supplements were matched for relative caffeine dose, about 5 mg of caffeine per kg of body weight. Any difference between them therefore can't be put down to one simply containing more caffeine. Participants took the capsules 60 minutes before the 30-second continuous jump test (30CJ), a valid and reliable anaerobic capacity test that is popular in team-sport settings.
The researchers tracked maximum jump height, mean jump height, peak power output (PPO), lowest power output, fatigue index and total number of jumps.
What It Found: The Numbers
The standout result was peak power output. Guarana was the only treatment to reach statistical significance there:
- Guarana vs placebo: PPO up 4.0% (dz = 0.82, p = 0.022)
- Guarana vs pre-test values: PPO up 4.4% (dz = 0.55, p = 0.041)
- Caffeine: no statistically significant PPO effect (p > 0.05)
For maximum jump height, mean jump height and lowest power output, there were no significant main effects. Even so, the effect sizes for guarana versus placebo pointed in a favorable direction (dz = 0.73, 0.86 and 0.58 respectively). The authors also noted a reduction in total jump volume alongside these trends.
The authors read this as guarana producing more mechanical output per jump, even though the athletes completed fewer jumps overall.
The Catch: Guarana Did Not Beat Caffeine
This is the part the clickbait version of the story would skip. The two active treatments did not differ significantly from each other. Guarana did not statistically beat caffeine in this trial.
The head-to-head gaps were descriptive only, with guarana numerically ahead in:
- Mean jump height: +1.5%
- Peak power output: +1.4%
- Maximum jump height: +0.9%
- Lowest power output: +0.7%
Those are small margins, and the study did not show them to be reliable. "Guarana worked, caffeine didn't" is also a trap. Reaching significance against placebo while another treatment narrowly misses it does not prove the two differ. Caffeine's results pointed the same way, just without clearing the threshold. The honest summary is that both supplements may help, and guarana had the cleaner statistical signal for peak power.
Other Limitations
- Small sample: 18 participants limits statistical power and generalizability.
- Young, active men only: the findings can't be assumed to apply to women, older adults, elite athletes or people with different caffeine habits.
- Single acute dose: this tells us nothing about repeated use, tolerance or long-term effects.
- One test format: a 30-second jump test is a specific kind of anaerobic effort. It doesn't automatically translate to sprinting, lifting or sport performance.
- Mechanism unclear: the idea that guarana's multi-compound matrix offers "distinct metabolic advantages" is a hypothesis in the paper's framing, not something this trial demonstrated.
How to Use It: Practical Takeaways
Dose by caffeine, not by guarana weight. The study dosed guarana to deliver roughly 5 mg/kg of caffeine. Guarana products vary widely in caffeine content, so check the label for caffeine per serving and calculate from that. As simple arithmetic, an 80 kg person would be targeting about 400 mg of caffeine. That is a large single dose, and it sits at the level commonly cited as a daily upper limit for healthy adults. Many people may prefer to start well below it.
Timing: The protocol used capsules 60 minutes before the effort. That's a reasonable starting point for pre-workout timing.
Form: The trial used capsules. Powders, energy drinks and blended pre-workouts may differ in how much caffeine they deliver and how quickly, so don't assume the same results.
Who it might suit: Active people doing repeated explosive efforts such as jumping, sprinting or team-sport drills, who already tolerate caffeine well and want to try a plant-based source.
Who should skip it or be cautious:
- Anyone sensitive to caffeine, or prone to jitters, anxiety, palpitations or poor sleep
- People with heart conditions, high blood pressure or who are pregnant (talk to a clinician first)
- Athletes training in the evening, when late caffeine can hurt sleep
- Anyone already getting caffeine from coffee, pre-workouts or energy drinks, since guarana is caffeine and the totals add up
A sensible approach is to trial any dose in training, never for the first time on competition day, and to lower the dose if side effects appear.
The Bottom Line
With caffeine matched at ~5 mg/kg, guarana raised peak power by about 4% over placebo and caffeine did not reach significance. But guarana and caffeine were statistically indistinguishable from each other, and the numerical edges for guarana were small. This is an encouraging early signal from a small, well-controlled trial, not proof that guarana is a superior ergogenic aid. Treat it as a viable caffeine source worth testing, dosed carefully by its caffeine content.
