The seeds of the guarana, a climbing shrub native to South America, are being added to energy drinks and teas, dietary supplements and other food products in the United States at a rapid pace. They are packed with up to four times the amount of caffeine found in coffee beans, and are reported to be a stimulant that boosts energy, fights fatigue, increases stamina, and increases mental alertness.
Amazonian Indians have used guarana for centuries during fasting periods to help suppress the appetite, and modern man is continuing the tradition by adding it to weight-loss products. Several small studies have hinted that guarana does indeed help with weight control, but the studies are usually short-term and involve products with additional ingredients.
According to Sloan-Kettering, an in vitro study suggested Guarana may even have chemopreventative effects.
The claims that guarana boosts energy and mental function make sense because of the high amounts of caffeine, Kevin A. Clauson, associate professor at Nova Southeastern University in Fort Lauderdale, Fla., told the Wall Street Journal. A British study gave college students guarana tablets and tested their memory, mood, and alertness. They scored higher than they scored on the same tests given on a different day after taking a placebo.
The boost to scores after taking guarana, according to British researchers, was higher than would have been expected with caffeine alone. While the reason is unknown, senior author Andrew Scholey believes that saponins, a class of phyto-chemicals found in guarana, may enhance blood flow to the brain.
With so many products containing guarana entering the marketplace, it's easy to over-consume since, unlike coffee, the amount doesn't have to be listed on guarana drinks.
Guarana should be avoided by people who are sensitive to caffeine, and Clauson says that pregnant women should be wary because of it's high levels of caffeine. Those with heart problems should also be cautious since severe heart-related reactions have been reported.
Guarana may interact with numerous drugs including MAO inhibitors, lithium, aspirin, ephedrine, clozapine, and acetaminophen.
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