Guarana
EVIDENCE: MODERATEAlso sold as: Paullinia cupana, guaraná seed extract
Guarana is a Brazilian seed that is naturally rich in caffeine. Its effects on alertness and focus are mostly the effects of that caffeine. Labels that list guarana without a caffeine amount leave the caffeine dose unknown.
Compiled by iSupplementReviews editorial team ·Researched 2026-10-16 · 3 sources
- Type
- Botanical stimulant (caffeine source)
- Studied dose
- 37.5–300 mg extract in single-dose cognition studies
- Best form
- extract with a stated caffeine content
- Our rating
- MODERATE — Several human trials — limits in size, duration, or independence
What is guarana?
Guarana (Paullinia cupana) is a climbing plant from the Amazon whose seeds are a concentrated natural source of caffeine. It is common in energy drinks and sodas in Brazil.
Other names and forms
Guaraná, Paullinia cupana seed extract, guarana powder. Extracts vary widely in caffeine content, so the caffeine number matters more than the guarana number.
Where does guarana come from?
The seeds of a vine grown in the Brazilian Amazon. The seeds are roasted and ground or extracted.
How does guarana work in the body?
Caffeine blocks adenosine receptors, which reduces drowsiness and raises alertness. Guarana also contains tannins and small amounts of related stimulants (theobromine, theophylline).
What is guarana claimed to do?
Boost energy, sharpen focus, “stimulate metabolism” and support weight loss.
What does the research show?
| Claim | Evidence | Dose studied | Verdict |
|---|---|---|---|
| Alertness and attention | Single-dose RCTs + meta-analysis | 37.5–300 mg extract | Short-term positive |
| Weight loss on its own | No good standalone trials | — | Insufficient |
| Long-term metabolic benefit | None | — | Not shown |
Cognition
Single doses of guarana extract improved attention and memory tasks in small trials. Kennedy et al. (2004) tested 37.5–300 mg of extract in healthy volunteers and found better scores on several tasks in the hours after a dose. Hack et al. (2023) pooled the human studies and found a modest benefit for some attention measures.
Weight
Weight-loss claims rest on products that combine guarana with other stimulants. Pittler et al. (2005) reviewed adverse events in herbal weight-loss supplements and flagged stimulant combinations as a recurring safety concern.
What dose was studied?
| Goal | Dose | Duration |
|---|---|---|
| Attention and mood | 37.5–300 mg extract | Single doses |
Side effects
Those of caffeine: jitteriness, sleep trouble, fast heartbeat, stomach upset.
Drug interactions
- Other stimulants and caffeine: effects add up (moderate).
- Blood thinners: guarana may slightly slow clotting (minor, theoretical).
- Certain antibiotics and fluvoxamine: can slow caffeine breakdown (moderate).
Who should not take guarana?
People who are pregnant, sensitive to caffeine, or have heart rhythm problems, anxiety disorders or uncontrolled high blood pressure.
What the authorities say
Health regulators treat guarana as a caffeine source. The U.S. FDA says up to about 400 mg of caffeine a day is not generally linked to harm in healthy adults; guarana counts toward that total.
What to know about guarana
Guarana works mainly through caffeine, with short-term evidence for alertness. A label that lists guarana without a caffeine figure leaves the stimulant dose unknown.
Frequently asked questions about Guarana
Does guarana contain caffeine?
Yes. Guarana seeds contain more caffeine by weight than coffee beans. Most of guarana's effects on energy and focus come from that caffeine.
Does guarana help weight loss?
There is no good evidence that guarana alone causes weight loss. Studies that reported weight changes used it inside multi-ingredient products, so its own contribution is unclear.
Is guarana safe?
At modest amounts it behaves like caffeine. People sensitive to caffeine, pregnant people and those with heart rhythm problems should count it toward their caffeine total.
References
- [1]Kennedy DO et al. — Improved cognitive performance in human volunteers following administration of guarana (Paullinia cupana) extract (Pharmacol Biochem Behav, 2004)
- [2]Hack B et al. — Effect of Guarana (Paullinia cupana) on Cognitive Performance: A Systematic Review and Meta-Analysis (Nutrients, 2023)
- [3]Pittler MH et al. — Adverse events of herbal food supplements for body weight reduction: systematic review (Obes Rev, 2005)
Products we reviewed containing Guarana
Based on recorded labels or seller-described formulas. Inclusion does not establish a match to the strains, preparations or amounts studied here; check each review's disclosure limits.