There is exactly one ingredient in energy drinks that actually perks you up, a new study suggests: good old caffeine. None of the other ingredients that supposedly give the drinks an edge actually improve alertness, researchers concluded. They gave participants water, water with caffeine, and 5-Hour Energy, and had them attempt to respond to changing letters on a screen while scanning their brains, LiveScience reports.
The result? There was zero difference between the group that had the caffeinated water and the group that had the 5-Hour Energy. "A lot of people take the energy drinks because they think they have that extra boost over caffeine," one of the researchers said. But a cup of coffee "would do you just as well," assuming it had the same amount of caffeine. Of course, that's usually not the case; each 2-ounce 5-Hour Energy bottle packs about as much caffeine as two cups of joe. (Read more energy drink stories.)