The herb guarana has long been used as a stimulant because of its high caffeine content. Native to the Amazon rain forest, guarana's use in traditional herbal medicine includes headache treatment and fever alleviation. Commercially, it's promoted for several purposes such as suppressing appetite, losing weight and reducing fatigue. Manufacturers commonly add it to energy drinks and sports beverages for purported benefits such as improved mental function and enhanced sports performance.
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Rich in Caffeine
Guarana seeds contain more caffeine than any other known plant, according to a September 2010 article in the journal "Evidence-Based Complementary and Alternative Medicine." The seeds contain between 2 percent and 7.5 percent caffeine and about four times as much caffeine as coffee on average, according to the review. Guarana also contains a small amount of other alkaloids in the caffeine family such as theobromine and theophylline.
Potential for Caffeine Overload
Guarana stimulates the nervous system, but its effects last longer than coffee, according to the authors of the "Evidence-Based Complementary and Alternative Medicine" review. The abundant use of guarana combined with other sources of caffeine in energy drinks raise concern over potential health problems from excess stimulants. The review reported that emergency-room visits because of caffeine overdose from guarana-containing products are becoming common.
Increases Risk of Dehydration
Guarana-containing energy drinks are commonly promoted in conjunction with sports activities. The caffeine from guarana, however, exerts diuretic effects. Caffeine promotes water loss at a rate of 1 milliliter of water per milligram of caffeine, according to a safety review published in the 2008 edition of the "Journal of the American Pharmacists Association." This increases your risk of dehydration. Consuming caffeine-containing beverages during athletic activities is not a good idea, according to the review.
The side effects reported from guarana use are related to its caffeine content and include anxiety, insomnia, rapid heart beat and upset stomach. There are rare reports of seizures in four young adults after they consumed energy drinks containing guarana and other ingredients, according to NYU Langone Medical Center. The typical dose of guarana only supplies about 50 milligrams of caffeine, which is about the same as 1/2 cup of strong coffee. A moderate amount of caffeine, which is about 200 milligrams, is not considered harmful, according to the U.S. Food and Drug Administration. Guarana, however, is commonly found with other caffeine ingredients in energy drinks, and this increases the total caffeine content.