Guarana extract is a form of guarana, known as Brazilian cocoa, which is derived from a scrub that is native to the Amazon. Guarana extract contains caffeine and functions as a stimulant; therefore, it is included in some energy drinks.
Because of its caffeine content, guarana acts as an appetite suppressant and weight-loss aid. Studies have shown that it increases metabolism and reduces body fat. Common side effects of consuming products containing guarana extract include nervousness and insomnia.
Guarana is not recommended to be used by women who are pregnant or lactating or by people with cardiovascular disease. Possible drug interaction occurs when taken along with lithium, theophylline or clozapine.