Energy Drinks comparison

Taurine

What is it?: One of the most abundant amino acids in your brain, where it can act as a neurotransmitter—a chemical messenger that allows your cells to communicate with one another. You'll find anywhere from 20 mg to 2,000 mg of taurine in most 16-ounce energy drinks.

Does it work?: Scientists aren't sure, but it doesn't seem likely. When taurine is dumped into your bloodstream—when you down a Red Bull, for instance—it can't pass through the membranes that protect your brain, says Neil Harrison, Ph.D., a professor of pharmacology at Weill Cornell Medical College.

But even if it could, Harrison's research suggests that taurine might behave more like a sedative than a stimulant. When he and his team applied the amino acid to the brain tissue of rodents, they discovered that it mimicked a neurotransmitter called gamma-aminobutyric acid, or GABA, a chemical that slows brain activity.

Is it safe?: Taurine is probably fine in small doses, but chug too many energy drinks and the picture becomes less clear. According to a recent case report from St. Joseph's Hospital in Phoenix, Arizona, three people had seizures after drinking approximately two 24-ounce energy drinks in a short period of time. However, the researchers don't know whether to blame the taurine or the caffeine, or what role preexisting health conditions may have played.

The fact is, there's been little research on taurine consumption in humans, so it's impossible to conclude whether it's safe to consume in high doses. Of course, there's no strong evidence to support its role as an energy booster, either.
http://www.menshealth.com/mhlists/effectiveness_of_energy_drinks/Taurine.php