Guarana

Studies in people

• No harm found

  Cancer-related fatigue²

  In cancer patients, guarana did not reduce fatigue any better than a placebo.

• Open question

  Memory and thinking in older adults³

  In older people, taking guarana for a long time did not clearly improve memory or thinking.

• Open question

  Thinking, anxiety and sleep⁴

  In people, guarana taken once did not change thinking, anxiety or sleep, but long-term effects are still unknown.

• No harm found

  Herbal supplement risks⁵

  Guarana is not known to cause serious health risks when consumed properly, research found.

• Benefit

  Oxidative stress in the body⁷

  In people, guarana seed powder raised antioxidant enzymes and lowered signs of oxidative stress in the blood.

• No harm found

  Mood and anxiety⁸

  In people, taking guarana for five days made no difference to mood, anxiety or well-being.

• Concern

  Caffeine levels in powders⁹

  Some guarana powders sold in Korea had enough caffeine to exceed daily limits for teens in one serving.

Animal and lab studies only

• Benefit

  Blood sugar control¹²

  In lab studies, guarana powder's insoluble-bound polyphenols inhibited alpha-glucosidase more strongly than its soluble ones.

• Benefit

  Blood cholesterol levels¹³

  In lab studies, guarana seed powder extract blocked some cholesterol from being taken up by cells.

• Benefit

  Cholesterol and heart health¹⁴

  In lab studies, guarana showed antioxidant activity and less LDL oxidation, which may help explain heart benefits.

• Benefit

  Blood clotting¹⁵

  Guarana seeds contain natural compounds that may help stop blood from clotting too easily, though scientists are still studying this.

• Benefit

  Weight gain in rats¹⁶

  In animal studies, guarana seed powder stopped rats on a Western diet from gaining weight.

Study type not stated

• Open question

  Human health effects¹⁰

  Guarana may help with energy, inflammation and weight, but scientists say there are not enough studies in people yet.

How it’s made and used

• Fat burning during exercise⁶

  In men, guarana in a blend shifted how the body made energy, using more carbs and less fat.

• Caffeine content in energy drinks¹¹

  Guarana contains a lot of caffeine, and some product labels do not make this clear.

• Muscle fat burning¹⁷

  In animal studies, guarana changed how rats' muscles used fat, but decaffeinated guarana did not.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.