Not thoroughly, and not together. Many energy drinks contain high levels of herbal substances like guarana, ginseng, gingko biloba, taurine, and other stimulants that are unproven and not analyzed by the FDA. The synergistic effect of these substances has not been properly tested. One of the most common energy drink ingredients, taurine, has not been assessed or approved as a food additive for use in conventional foods by the FDA; it is only considered GRAS (“Generally Recognized as Safe”) for use by the Flavor and Extract Manufacturers Association.
The New York Times published an extensive article on these ingredients in 2013 under the headline, “Energy Drinks Promise Edge, but Experts Say Proof Is Scant,” in which author Barry Meier notes that “the energy drink industry is based on a brew of ingredients that, apart from caffeine, have little, if any benefit for consumers.”
Due to concerns over the effects of taurine, France, Denmark, Norway, and Uruguay outlawed Red Bull outright for several years. The European countries were forced to legalize it in 2008 because of EU regulations, but French authorities remain skeptical of the drinks’ ingredients and their neurophysiological effects. (Red Bull is still illegal in Uruguay.)
Given the dearth of research, the fact that energy drink companies aren’t required by the FDA to disclose the quantity of these ingredients in their products, and the drinks’ alarming amounts of caffeine and sugar, it is no wonder that in 2011 alone there were 20,783 emergency room visits involving energy drinks.