Guarana
Paullinia cupana, a climbing plant from the Amazon
The seed of an Amazon climbing plant, naturally rich in caffeine, and studied mostly for attention, thinking and mood, and for tiredness in people having cancer treatment. Here is every study in people we could find, sorted from each study's summary.
- Part used: seed
- Taken as seed powder or extract
- Often a single dose
From every paper to the studies that matter
Most research on guarana is in the lab or about the plant and the drinks made from it. Only a small share tests it in people, and that is what this page is about.
-
425 papers mention guarana.Every record in PubMed, all years
-
62 are about people.The rest: 143 lab and animal studies, 66 reviews, 154 on chemistry, farming and more
-
21 give guarana on its own.25 more test it in an energy drink or inside a blend
-
17 are randomised against a placebo.Randomised controlled trials In a randomised controlled trial, people are put into groups by chance, one taking the treatment and one a placebo or other comparison. Chance spreads differences such as age and health evenly, so a difference between the groups is more likely to be down to the treatment., the strongest kind of study
Bar lengths use a square-root scale so the small numbers stay visible.
How much research there is
- 21 studies giving guarana to people
- 17 of them randomised against a placebo A placebo-controlled trial compares a real treatment with a dummy that looks the same, the placebo. People often feel better when they expect to, so comparing against a placebo shows how much of the change comes from the treatment itself.
- 609 people taking part, where studies say
- 15 systematic reviews A systematic review searches for every study on a question in a set, written-down way, judges the quality of each and sums up what they show together. Many include a meta-analysis. The Atlas lists these as pooled reviews. pooling the trials
Studies in people, by year published
Guarana on its own. More than half were published since 2016.
What the studies looked at
Each study can measure several things. Choose a topic to see its studies in the list below.
Studies in people with a diagnosed condition are counted here and listed with their population. We describe what they measured, not what they might treat. Most studies also report safety; see below.
What was tested, and how much
Guarana is taken as dried seed powder or as extracts such as PC-18, and how much caffeine it holds varies (up to about 5% of the seed), so the same number of milligrams can mean different amounts of caffeine. Many studies gave one dose shortly before testing, while studies in people having cancer treatment mostly gave 75 to 100 mg a day.
Daily amount, one dot per study
Studies per extract
Named extracts are the maker's brand. "Not named" means the study didn't say.
Have a label with a %? Work out the caffeine in your own label
All studies in people
Filter the list, then open a study on PubMed. Each row comes from the study's published summary. Studies of caffeine on its own aren't included, because caffeine alone isn't guarana.
| Study | Who took part | People | Extract and daily dose | Length |
|---|---|---|---|---|
| Rekik 2026Crossover, placebo | Male amateur soccer players | 32 | Not named, 300 mg | – |
| Amaritei 2025Single-arm or open-label | University students | 33 | Not named, 2,000 mg | 1 weeks |
| Estrázulas 2024Crossover, placebo | Under-17 male soccer players | 27 | Not named, 3,000 mg | – |
| Talik 2024Crossover, placebo | Healthy adults | 20 | Not named, 500 mg | – |
| Penna 2024Crossover, placebo | Endurance-trained cyclists and non-cyclists | 11 | Not named, 500 mg | – |
| Gurney 2023Crossover, placebo | Healthy active adults | 25 | Not named | – |
| Pomportes 2019Crossover, placebo | High-level modern pentathlon athletes | 10 | Guarana complex, 300 mg | – |
| Sette 2018RCT, placebo | Early breast cancer patients with chemotherapy fatigue | – | PC-18, 75 mg | – |
| Martins 2017RCT, placebo | Head and neck cancer patients on chemoradiotherapy | 60 | Not named, 100 mg | – |
| Pomportes 2017Crossover, placebo | Healthy exercising adults | 24 | Guarana complex | – |
| Palma 2016Single-arm or open-label | Advanced cancer patients with anorexia | 30 | Not named, 100 mg | 4 weeks |
| Yonekura 2016Single-arm or open-label | Healthy overweight adults | 12 | Not named, 3,000 mg | 2 weeks |
| del Giglio 2013RCT, placebo | Patients with solid tumours on chemotherapy | 40 | PC-18, 75 mg | 6 weeks |
| Silvestrini 2013Crossover, placebo | Healthy volunteers | 27 | Not named, 1,050 mg | 1 weeks |
| Oliveira 2013Single-arm or open-label | Breast cancer survivors with hot flashes | 18 | Not named, 100 mg | 6 weeks |
| de Oliveira Campos 2011Crossover, placebo | Breast cancer patients on chemotherapy | 75 | Not named, 100 mg | 3 weeks |
| da Costa Miranda 2009Crossover, placebo | Breast cancer patients on radiotherapy | 36 | Not named, 75 mg | – |
| Haskell 2007Crossover, placebo | Healthy young adults | 26 | PC-102 | – |
| Kennedy 2004Crossover, placebo | Healthy young adults | 28 | Not named, 75 mg | – |
| Galduróz 1996RCT, placebo | Healthy elderly volunteers | 45 | Not named | – |
| Galduróz 1994RCT, placebo | Healthy volunteers | 30 | Not named | – |
What's known about safety
-
In trials
The trials are mostly small and short, and the reviews we opened don't report side effects. Guarana's caffeine can cause sleeplessness, restlessness and palpitations at high intakes, and case reports link very large amounts to heart rhythm problems.
Hack 2023, review of 8 trials; de Araujo 2021, review of 7 trials; FSA, food supplements containing caffeine, Sept 2024; Ciszowski 2014, case report
-
In the UK
Guarana fruit and seed were eaten in the EU before May 1997, so they aren't a novel food and can be sold in food supplements. Its caffeine counts towards the FSA's advice of no more than 400 mg a day for most adults. We found no guarana product registered with the MHRA as a traditional herbal medicine.
EU Novel Food Status Catalogue (fruits and seeds, not novel); FSA, food supplements containing caffeine, Sept 2024; MHRA list of traditional herbal registrations, Oct 2025
-
Check first
It isn't recommended in pregnancy, while breastfeeding or under 18, and in pregnancy all caffeine should stay under 200 mg a day. Speak to a doctor first with stomach ulcers, high blood pressure, heart rhythm problems or an overactive thyroid, or if you take MAOI antidepressants or other medicines.
EMA herbal monograph on guarana seed, 2013; FSA, food supplements containing caffeine, Sept 2024
Where these studies come from
We list every published study of guarana in people. Caffeine on its own isn't counted, and guarana in energy drinks or blends is counted as in a blend. This first version is built from each study's summary; full-paper checks come next.
-
We search
PubMed, the world's main library of medical research, for every paper on L-theanine.
-
We keep studies in people
Lab and animal work is counted but left out of the list, because it doesn't tell you what happens in people.
-
We note the basics
Who took part, how many, how much and for how long, from each study's published summary. A second check corrects what the first read gets wrong.
-
We read them in full
Results appear once we've read the whole paper and checked every number. The date at the top shows when this entry was last updated.
Download the study list
Every study in people as a spreadsheet, 21 rows, free to reuse with a link back.
Versions
Each update to the data gets a new version number, so you can tell what changed and when.
See every version
1.0 · 24 Oct 2026. First release. Every published study giving guarana on its own to people is listed from its summary. None is read in full yet.
Related
- What are nootropics? A UK guideWhat nootropics are, which ones have real evidence behind them, what UK law says and how to choose a supplement.
- Nootropic stacks: a beginner's guideA nootropic stack is two or more supplements taken together for focus, memory or calm. Here's which pairings have research behind them, what L-thea...
- Free toolCaffeine calculator