This information describes the common uses of Guarana, how it works, and its possible side effects.

Common Name

Guarana gum, Guarana seed, Zoom cocoa, Brazilian cocoa

How It Works

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.

Purported Uses

  • 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.

Do Not Take If

  • You are taking anticoagulant or antiplatelet medications: Guarana has antiplatelet activity and can have additive effects.

Side Effects

  • Increased water lost from the body as urine
  • Insomnia

Case Reports

  • 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.