Guarana (Paullinia cupana) is a Brazilian climbing shrub whose seeds contain substantial amounts of caffeine as well as two other alkaloids also found in tea and coffee – theobromine and theophylline; it also contains tannins. The seeds are used to make a paste that is used medicinally. Guarana is also the base for the most popular soft drink in Brazil. Natives of the Amazonian rain forest chewed the seeds or added them to foods or drinks in order to increase alertness and reduce fatigue. It is not widely used as a supplement in the UK but one major chocolate manufacturer launched a chocolate bar in 2002 that contained guarana promoting it as a ‘tasty stimulating snack’.
Guarana seeds contain about twice as much caffeine as coffee beans and so, given the well-known stimulant effects of caffeine as well as theobromine and theophylline, it clearly would act as a general CNS stimulant. The caffeine in guarana is sometimes referred to as guaranine to make it sound unique. The caffeine content of guarana extracts may vary between 30 and 50% depending upon brand: one 200 mg tablet contains around 80 mg of caffeine and one cup of brewed coffee contains about 100 mg. A can of cola contains about half the caffeine in a cup of brewed coffee but it varies according to brand and variety. Some other soft drinks marketed upon their ability to boost energy levels and ‘give you wings’ contain several times the concentration of caffeine found in cola drinks.
Guarana is claimed to increase alertness, ‘boost’ energy levels and reduce fatigue. Given that caffeine and the other alkaloids in guarana and in tea and coffee are accepted to be CNS stimulants such effects are to be expected from consuming any of these.
Caffeine, and therefore guarana, is known to have some capacity to boost athletic performance in large doses. For this reason, until 2004 the International Olympic Committee classified caffeine as a restricted substance and set a threshold on the amount of caffeine (12 mg/L) that is permissible in competitors’ urine samples. To exceed this threshold requires a large caffeine intake – about eight cups of brewed coffee, ten 200 mg guarana tablets, 18 cans of cola or 800 mg of caffeine (note these figures are for illustrative purposes only and will obviously vary depending upon body size and other factors).
Claims that tolerable doses of caffeine promote weight loss have not been substantiated.
The adverse effects of taking large doses of guarana are similar to those experienced when large amounts of strong coffee are consumed: nervousness, insomnia, palpitations, stomach irritation and a rise in blood pressure. Whether a supplemental source of caffeine is useful or desirable must be left for individual consumers to decide. Supplements typically contain up to 200 mg of guarana extract.