The quantity of caffeine in guarana is higher than that contained in equivalent weight of coffee beans. Guarana can contain 3.6-5.8% caffeine, while coffee has 2%.
The derivatives of xanthine theobromine and theophylline are two substances with stimulant and invigorating properties.
Other derivatives of xanthine are the methylxanthines which can stimulate the muscular system and overcome the feeling of fatigue. Tannins are also beneficial because they seem to promote adrenaline secretion.
Guarana increases heart rate and contractility, raises blood pressure, inhibits platelet aggregation (a study in rabbits showed a 37% decrease in platelet aggregation), stimulates gastric acid secretion, causes diuresis, relaxes bronchial smooth muscles, and stimulates the release of catecholamines.
70% of guarana production is used in energy drinks (e.g. Red Bull) and the rest in dietary supplements aimed at enhancing athletic performance or for weight loss.
Guarana is believed to:
A specific daily dosage has not been determined but should not exceed 3 grams of powder. It is not recommended as a coffee alternative. The pills in supplements provide 40-200 mg (this dosage is considered low). Generally, when used for stimulation, continuous intake of large quantities for more than a week is not recommended, due to its caffeine content.
Side effects are generally the same as those of coffee. They include sleep problems, anxiety, stomach issues, and rapid heartbeat. High doses of caffeine can increase heart rate and blood pressure - note that individuals with hypertension should not drink coffee.