You've probably experienced this before. You're on vacation, but your bowel movements aren't responding well. It's like you forgot to bring them on vacation too. An article over at The Atlantic explains why as many as 40 percent of people experience constipation while they're away from the throne at home.

The reason is the 100 over trillion intestinal microbes in your gut. They control how much you poop.

When you're at a foreign place, other than what you're used to, those microbes stop working. Because...

They're shy!!!

According to Brooke Alpert, a New York-based registered dietician, it's because your intestinal microbes can tell they're in a new environment and it makes them kind of shy.

"Any time you leave your general habitat, it's throwing your gut microflora off balance," Alpert explained. Introverted microbes aren't the only thing ruining your morning constitutional, however.

"...sitting on a plane or in a car for long periods of time can cause the intestines to clog; ignoring the urge to go while in the air or on the road can also make it more difficult once you finally sit down on the toilet.

Time differences can also pose a problem. Many people have a normal bowel-movement routine, pooping at regular intervals throughout the day. But when jetlag or a new time zone shifts that schedule ahead or backwards by a few hours, it can mess up that routine, causing constipation.