Guarana contains caffeine, and therefore has stimulant effects. Long-term effects of using guarana are not known.
Guarana is extracted from the seed and gum of a plant found in the Amazon Basin. It is commonly used in beverages because of its flavor and because it contains high levels of caffeine. Scientists are very familiar with how caffeine affects the body: it prolongs the action of the sympathetic nervous system (responsible for our “fight or flight” response) and therefore stimulates the brain, heart and muscles, and increases blood pressure.
Guarana showed anticancer, neuroprotective, and anti-anxiety properties in laboratory studies. An epidemiological study showed that guarana intake protected elderly subjects against metabolic disorders. Guarana improved fatigue in healthy young adults and in breast cancer patients undergoing chemotherapy, but was not useful in reducing fatigue following radiation therapy. More studies are needed.
As an appetite suppressant
No scientific evidence supports this use.
As a stimulant
Guarana contains caffeine, which has known stimulant effects.
To treat fatigue
Guarana was shown to be effective against mental fatigue in young healthy adults. Its effects in treating fatigue in cancer patients are mixed.
To improve sexual performance
No scientific evidence supports this use.
Do Not Take If
You are taking anticoagulant or antiplatelet medications (guarana has antiplatelet activity and can have additive effects.)
Diuresis (increased water lost from the body as urine)
Premature ventricular contractions have been reported with use of guarana.
Seizures were reported in four healthy young adults following consumption of energy drink that contained guarana along with other ingredients.
Guarana, a bushy plant prevalent in the Amazon Basin, has been used in traditional medicine to treat fevers, headaches, and dysentery. Actions of guarana are attributed primarily to caffeine present in its seeds (2)(3). It is promoted as an appetite suppressant, stimulant, as an aphrodisiac, and to alleviate fatigue. There are extensive data regarding caffeine and its activity.
In vitro studies indicate that guarana has chemopreventive (11)(12), neuroprotective, (13) and anxiolytic (14) properties. Epidemiologic data suggest its protective effects against metabolic disorders in elderly population (15). Improvements in cognitive performance and mental fatigue were also observed following supplementation of guarana in healthy adults (16).
In studies of breast cancer patients, guarana did not confer any protection against post-radiation fatigue (17), but was useful as a short-term treatment for fatigue during chemotherapy (22). Further research is needed.
Central nervous system stimulation
Mechanism of Action
Many of guarana’s effects are thought to be due to its high caffeine content. Caffeine’s actions include CNS stimulation, cardiac stimulation, diuresis, increase in blood pressure, inhibition of platelet aggregation, skeletal muscle stimulation and causing hyperglycemia (2)(3). Guarana demonstrated antioxidant effects by inhibiting lipid peroxidation (19). Chronic exposure to Guarana seed extract produced an anxiolytic effect involving the dopaminergic and serotonergic neurotransmission systems (14).
Premature ventricular contractions were reported following consumption of guarana (7).
Seizures were reported in four healthy young adults following consumption of energy drink that contained guarana along with other ingredients (18).
Anticoagulant or Antiplatelet drugs: Guarana demonstrated antiplatelet activity and can therefore have additive effects (20)(21). Amiodarone: A study done in rats showed that Guarana extract decreases the bioavailability of amiodarone (24).
Herb Lab Interactions
May cause arrhythmia
Blood pressure may be elevated (7)
Dosage (OneMSK Only)
McGuffin M. A Botanical Safety Handbook. Boca Raton (FL): CRC Press; 1997.
Gruenwald J, et al. PDR for Herbal medicines, 2nd ed. Montvale (NJ): Medical Economics Company; 1998.
Schulz V, et al. Rational Phytotherapy: A Physicians Guide to the Use of Herbs and Related Remedies, 3rd ed. Berlin (Germany): Springer; 1998.
Fetrow CW, et al. Professional’s Handbook of Complementary and Alternative Medicines. Philadelphia: Springhouse; 1999.
McEvoy GK, et al. AHFS Drug Information. Bethesda (MD): ASHP; 1998.
Brinker F. Herb Contraindications and Drug Interactions, 2nd ed. Sandy (OR): Eclectic; 1998.