How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Guarana
Guarana: a small dose of extract (37.5 to 75 mg) slightly improves attention and memory for a few hours in small trials. No proven fat-burning effect.
Benefits
- Attention: 75 mg of extract, providing only 9 mg of caffeine, improved attention and mental arithmetic in 28 young adults over the six hours following ingestion.
- Memory and mood: in 26 people, a dose of 37.5 to 300 mg of extract improved memory and made them feel more alert and happier; the two smallest doses performed best.
- Mental fatigue: in 129 young adults, a drink containing vitamins, minerals, and guarana made them faster and more accurate during an hour of tasks, and curbed mental fatigue.
- Perceived exertion: in 10 pentathletes, 300 mg of a guarana complex during 40 minutes of running lowered perceived exertion, like 200 mg of caffeine, and accelerated post-run information processing.
- Fasted running: in 40 active men, vitamins and minerals with guarana before 30 minutes of running slightly lowered perceived exertion and improved working memory.
- Fatigue under chemotherapy: in women treated for breast cancer, 50 mg twice daily for 21 days improved fatigue scores compared to placebo, with no serious adverse effects.
Precautions
Blood pressure: a mixture of green tea and guarana providing 200 mg of caffeine three times daily raised blood pressure by about 7 and 5 mmHg over 24 hours, with a clear effect on diastolic pressure. Mixtures with ephedra: two doses increased pulse (+9.4 beats per minute), pressure (+11.5 mmHg), and postprandial blood glucose; the authors consider these effects harmful in cases of hypertension or glucose intolerance. Limits: fat-burning: the green tea and guarana mixture increased energy expenditure by about 750 kJ more per day, without burning more fat; with bitter orange, no extra expenditure, and more carbohydrates burned instead of fat. Fatigue after radiotherapy: in 36 female patients treated for breast cancer, 75 mg daily did no better or worse than placebo on either fatigue or depression. Fatigue under chemotherapy, other cancers: in the placebo-controlled phase of a trial on 40 patients, the extract did no better than placebo. Few trials: the 2022 review on guarana and health highlights the lack of human studies, and most trials in this fact sheet involve 10 to 40 people.
Recommended dosage
Extract: 37.5 to 300 mg in a single dose in concentration trials, often 75 mg; 50 mg twice daily against chemotherapy-induced fatigue.
How to take it
- One dose, one-day effect: trials on concentration test a single dose and measure its effects over one to six hours.
- Small dose: 37.5 and 75 mg of extract performed better than 150 and 300 mg on memory and attention, in a trial of 26 people.
- Not just caffeine: 75 mg of extract contains only 9 mg of caffeine, and the authors consider that the effect does not come from caffeine alone.
- With a multivitamin: compared to the same multivitamin without guarana, the version with guarana performed better on a mental arithmetic test in 20 people.
- Around training: in sports trials, guarana is taken just before and during 30 to 40 minutes of moderate running.
Did you know?
Less is more: in a trial of 26 people, 37.5 and 75 mg of guarana extract had better effects on memory and attention than 150 and 300 mg.
What the studies say
This randomized, placebo-controlled study examined the effects of a vitamin and mineral complex with guarana, taken before fasted exercise, in 40 active men. The supplement led to a significant reduction in perceived exertion during exercise and improved the accuracy of numerical working memory and image recognition speed. These results suggest that consumption of this complex can positively impact memory performance and reduce perceived exertion during moderate physical effort.
Veasey RC, Haskell-Ramsay CF, Kennedy DO, Wishart K, Maggini S, Fuchs CJ, Stevenson EJ. — Nutrients (2015) — View the source study
Pairs well with
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more