A good chunk of regular coffee drinkers know that coffee isn’t just great at getting them awake in the morning—it also makes them get up and go poop. But while coffee’s laxative powers are well-known, it’s not clear why exactly this happens. To get to the bottom of this mystery, some scientists decided to do exactly what you’d expect scientists to: giving lab rats some coffee.

Their preliminary results, presented this weekend at a research conference aptly named Digestive Disease Week, seem to reaffirm a suspicion that coffee’s poop-making prowess has nothing to do with caffeine. Coffee might also kill off bacteria found in our guts.

Read more at Gizmodo.