Energy drink benders have been sending an alarming number of people to the emergency room lately. ER admissions have doubled since 2007, and lawmakers are now demanding to know what energy drink makers put in these brews.

Today, Senators Richard J. Durbin and Richard Blumenthal, along with Representative Edward J. Markey, mailed letters to 14 energy drink makers, basically asking, "What on Earth is going into these drinks?" The Congressmen want to know the exact amount of caffeine in these concoctions. And after increased attention from watchdog groups, they also want the makers of drinks like Monster, Rockstar, and Red Bull to come clean about why they've chosen to market their potions in certain categories (for example, 5-Hour Energy markets itself as a "dietary supplement," meaning it's subject to different regulatory guidelines than beverages like Pepsi's Amp). And if these companies have conducted any studies on the health effects of their drinks, they'll have to disclose them. The FDA has also been conducting its own investigation into these pick-me-up elixirs, which have played a roll in many heart attacks, dozens of deaths, and at least one "spontaneous abortion." 

Certain studies have suggested that the only "energizing" ingredient energy drinks contain is plain old caffeine. All that guarana and taurine and ginseng is just for show, according to science. So why exactly are so many people mixing a little too much Red Bull in their Red Bull vodkas ending up in the hospital? We might soon find out. And don't think lawmakers won't take action against energy drinks if they find anything suspicious. Remember how they neutered Four Loko

Inset photo: zoëSocial via Flickr