There’s nothing like a delicious cup of coffee in the morning — and for some, it triggers another morning routine involving a toilet. But why does a cup of joe make some people have to go? The latest installation of the American Chemical Society’s "Reactions" video series has answers.

Contrary to popular belief, coffee’s laxative nature doesn’t come from caffeine. Instead, acid in coffee can trigger a gut reaction in the stomach that prompts it to unload its contents into the intestines. The video notes that coffee also causes an uptick in hormones that jumpstart the large intestine. Scientists still aren’t sure exactly which specific coffee compounds are at play.

For better or for worse, coffee’s laxative features only affect a fraction of the population. While everybody poops, only some people poop after drinking coffee.