Guarana and thinking skills in older volunteers
What it found
In 45 healthy older volunteers, taking guarana for five months did not change memory, attention or other thinking skills compared with placebo or caffeine.
The authors say the results were mostly the same across the three groups.
What they found
Studies in people
Memory
Tests of immediate and recent memory showed no significant differences between the guarana, caffeine and placebo groups at any point.
Attention and psychomotor speed
All three groups improved on the Digit Symbol test by the end, but there were no differences between groups. The authors say this was likely due to learning.
Visual-spatial organisation
The guarana group improved on the Mosaic test, but their starting scores were already higher than the other groups. The authors say one isolated result is not relevant.
Anxiety and reasoning
There were no significant changes in anxiety levels or in reasoning ability (Raven test) in any group.
Side effects
Four volunteers reported burning in the stomach (three on guarana, one on caffeine), which improved with lower doses taken after meals. One volunteer on guarana stopped treatment because of a clinically confirmed fast heart rate.
Sleep
One volunteer on placebo had persistent insomnia that stopped when treatment was interrupted. No other sleep changes were reported.
What the authors conclude
“Results show that guarana, in the studied doses, did not cause enough alterations to characterize any detectable clinical manifestation.”
Also in their conclusions
- They say guarana, at the doses studied, did not cause enough alterations to produce any detectable clinical effect.
- They suggest that guarana's reputation comes mainly from its popularity and from the placebo effect, and that caffeine's stimulant action may explain some reported effects.
- They note that guarana is not totally free from side effects, as one volunteer stopped treatment due to tachycardia.
How it was done
Guarana is a Brazilian plant widely believed in popular medicine to stimulate brain function. The authors wanted to test whether long-term use actually improves thinking in normal, elderly people.
Forty-five volunteers over 60 years old, free of medications and with no significant health problems, were randomly split into three groups: placebo, caffeine, or guarana. They took two capsules a day for 150 days (guarana group got 1 gram of guarana daily; caffeine group got 25 mg daily; placebo got brown sugar). Thinking, sleep and anxiety were tested at the start, at 3 months and at 5 months.
What it can’t tell you
- This was a five-month study in healthy older volunteers. It cannot show whether guarana affects thinking in younger people or in people with memory problems.
- The authors note that the treatment time may have been too short, or the tests not sensitive enough, to detect any effect.
Who paid
- Authors work at
- Federal University of São Paulo, Brazil
The paper
- Title
- The effects of long-term administration of guarana on the cognition of normal, elderly volunteers
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Galduróz JC, Carlini EA (1996). The effects of long-term administration of guarana on the cognition of normal, elderly volunteers. Sao Paulo medical journal = Revista paulista de medicina. doi:10.1590/s1516-31801996000100003Free full textPubMed 8984582DOI
Summary written 29 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error