Scientific Name(s): Paullinia cupana Kunth var. sorbilis (L.)
Common Name(s): Brazilian cocoa, Guarana, Guarana gum, Guarana paste, Zoom
P. cupana or Paullinia sorbilis are fast-growing, woody, perennial shrubs native to Brazil and other regions of the Amazon. The trees have large leaves and clusters of flowers that bear orange-yellow fruits containing up to 3 seeds each, similar in size to a coffee bean. Guarana is the dried paste made from the crushed seeds of P. cupana.1, 2
Historically, guarana seeds were collected and dry roasted over fire; the kernels were then ground to a paste with cassava and molded into cylindrical sticks, which were then sun dried. Guarana has been traditionally used in South America and by Amazonian Indians to increase awareness and energy. In certain regions, the extract is believed to be an aphrodisiac and protectant against malaria and dysentery. In 19th century France, guarana became popular as an ingredient in beverages, due to its stimulant properties. In 1880, guarana was introduced as an official drug in the United States Pharmacopeia, where it remained listed until 1910. Natural diet aids containing daily doses of guarana (occasionally combined with glucomannan) have been advertised in the lay press. Guarana has also been used during periods of fasting to suppress appetite. Today, the most common forms of guarana include syrups, extracts, and distillates used for flavoring and as sources of caffeine by the soft drink industry. Indian tribes in Brazil use guarana for its stimulant properties in beverages such as tea or coffee; it is sometimes mixed with alcohol to make a more intoxicating beverage.3, 4, 5, 6, 7
In 1840, caffeine was identified as guarana's principal constituent, with levels ranging from 3% to greater than 5% by dry weight.7 By comparison, coffee beans contain approximately 1% to 2% of caffeine and the content in dried tea leaves varies from 1% to 4%.8 The related alkaloids theophylline and theobromine have also been identified in guarana. Guarana is high in tannins (primarily catechutannic acid and catechol), which are present in concentrations of 5% to 6% dry weight; these impart an astringent taste.8
Trace amounts of a saponin known as timbonine, related to compounds reported in timbo fish poisons used by Amazonian Indians, have been reported.4
Uses and Pharmacology
Cognitive stimulant/CNS effects
One study examined behavioral effects in rats and mice after acute and chronic guarana administration. Animals treated with guarana doses of 2,000 mg/kg showed no difference when compared with control groups in motor activity, tremor, or salivation parameters.10 Another study showed an increase in physical capacity when mice were subjected to a stressful situation, such as forced swimming, after 3 to 6 months of guarana treatment.11
In a small study, 3 groups of healthy volunteers 20 to 35 years of age were given placebo, caffeine 25 mg, or 1,000 mg of guarana containing 2.1% caffeine (21 mg) daily. After 4 days, no reproducible improvement in cognition was noted in any group according to neuropsychological testing, assessment of sleep quality, and a State-Trait Anxiety Inventory.12 In another small study, the effects of long-term guarana administration on the cognition of healthy, elderly volunteers was assessed. Guarana did not result in statistically significant memory improvement.13
In an Italian randomized, single-blind, crossover trial of 27 healthy volunteers, guarana 350 mg (2.5% caffeine) 3 times daily for 5 days did not produce any effects on psychological well-being, anxiety, or mood compared with placebo. However, a subpopulation of female participants reported an increase in self-acceptance scores.14
Some researchers suggest that the revitalizing effects of guarana result partly from its antioxidant action.10
Guarana's potential appetite suppressant and energy-inducing effects are likely related to its caffeine content. Numerous investigational studies have shown the sympathetic stimulant ephedrine, when combined with caffeine, demonstrates a synergistic effect on increasing metabolic rates, with subsequent increased energy expenditure (thermogenesis), as well as lipolytic actions.19 These effects resulted in statistically significant weight loss when guarana was combined with diet in short-term animal and clinical trials. However, a review reports a lack of unequivocal benefits of guarana over water or sports drinks.3
A study in rats with diet-induced hypercholesterolemia demonstrated reductions from baseline levels in total cholesterol and low-density lipoprotein cholesterol with guarana doses of 12.5, 25, or 50 mg/day for 4 weeks.20
The effects of a guarana extract (12.24 mg/g of caffeine) on 7 chemotherapeutic drugs used in the treatment of breast cancer were tested in vitro in a breast cancer cell line. Cell proliferation decreased about 20% to 25% with the extract alone, but guarana extract plus cyclophosphamide resulted in an 80% decrease in cancer cell population compared to the control group after 72 hours. Guarana added to the other 6 agents resulted in decreases in cell proliferation of 40% to 50%.21
Doses ranging from 75 mg to 1,000 mg daily have been used in limited clinical trials evaluating stimulant effects.9
Pregnancy / Lactation
Use is contraindicated. Low birthweight, birth defects, and premature birth have been documented with guarana use.22
The Food and Drug Administration (FDA) has ruled that caffeine is unsafe as a food additive when combined with alcohol (ie, alcoholic beverages with added caffeine).1, 23 In vitro, guarana extract inhibited aggregation of platelets, possibly due to inhibition of platelet thromboxane synthesis.24
Based on the caffeine content of guarana, interactions with clozapine, lithium, anxiolytic agents, pseudoephedrine, and antihypertensive agents are theoretically possible.25
Individuals sensitive to caffeine, including those taking herbal weight loss preparations, should use guarana with caution. Guarana use has led to excessive nervousness and insomnia.
Case reports of dysrhythmias and seizures related to overconsumption of energy drinks exist in the literature;3, 26, 27 however, most cases of toxicity in adults appear to be mild and clinically benign. Accidental overdose in children may be more serious.27, 28 Pure caffeine/guaranine is potentially fatal at a dose of 10 g.8
Because of its high tannin content, excessive use of guarana may lead to an increased risk of cancer of the oropharynx.29
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