Here's some more info for you about it. http://en.wikipedia.org/wiki/Guarana

I'd just be careful with herbs, I studied herbology for years, you need to be careful of any medications, presecribed or OTC you take, also along with (as in this case) foods or drinks...and remember a lot of these things are not approved by the FDA, so there is no regulation of purity, dosage, etc... I am very picky about where I buy these type of things, and the product brands.

L