Fatigue associated with chemotherapy

• In 2011 the Journal of Alternative and Complementary Medicine published a clinical trial in which 65 breast cancer patients receiving chemotherapy were given either a placebo or 50 mg guarana twice daily for 21 days. Compared to the placebo, guarana significantly improved chemotherapy-related fatigue. [Source]

Physical and mental performance

• In 2015 Nutrients published a double-blind, placebo-controlled, crossover study involving 40 active males which found that a vitamin and mineral complex with guarana taken before moderate-intensity exercise improved cognition speed and working memory post exercise, when compared with a placebo. [Source]

Mood and behavior effects

• In 2007 the Journal of Psychopharmacology published a double-blind study involving 26 participants which found that 75 mg of guarana improved cognition, increased alertness and improved mood when compared to a placebo. [Source]

Cognitive performance

• In 2004 Pharmacology, Biochemistry and Behavior published a double-blind, placebo-controlled study which compared the cognitive effects of guarana, ginseng and a combination of both substances in a group of 28 participants. Compared to the placebo all three treatments improved task performance throughout the day. [Source]