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 lab studies. A population study showed that guarana intake protected elderly subjects against metabolic disorders. A few small studies in cancer patients suggest guarana may help reduce chemotherapy-related fatigue, stabilize weight, and increase appetite. However, it did not reduce fatigue after radiation therapy, or in patients with head and neck cancers, and some symptoms worsened compared with a placebo. Further research is 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
Results from studies of guarana to treat fatigue in cancer patients are mixed, and in one study of head and neck cancer patients, some symptoms worsened. Additional research is needed.
To improve sexual performance
No scientific evidence supports this use.
You are taking anticoagulant or antiplatelet medications: Guarana has antiplatelet activity and can have additive effects.
Increased water lost from the body as urine
Seizures: In 4 healthy young adults following consumption of energy drinks that contained guarana along with other ingredients.
Vomiting, agitation, irregular heartbeat, high blood pressure, or nausea: With abuse or misuse of guarana-containing supplements.
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 populations (15). Improvements in cognitive performance and mental fatigue were also observed following supplementation withguarana in healthy adults (16).
A few small studies in cancer patients suggest guarana may help reduce chemotherapy-related fatigue, stabilize weight, and increase appetite (22)(25)(26). However, it did not reduce fatigue post-radiation (17) or in patients with head and neck cancers, and some symptoms worsened compared with a placebo (27). Further research is needed.
Central nervous system stimulation
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).
Vomiting, agitation, tachycardia, hypertension, or nausea: Pediatric cases with abuse or misuse of guarana-containing supplements (28).
Tachycardia: In 2 women consuming guarana-containing supplement/energy drinks (29).
Premature ventricular contractions: In a 25-year-old woman with pre-existing mitral valve prolapse following consumption of guarana (7).
Seizures: In 4 healthy young adults following consumption of an 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).
May cause arrhythmia
Blood pressure may be elevated (7)
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