BY KORIN MILLER
It’s one of those weird things everyone knows, but nobody talks about: When you get sick with a stomach bug, it’s pretty likely you’re also going to get the runs. Apparently, scientists aren’t totally sure why this happens, so an international team of researchers conducted a new study to try to get to the bottom of the issue.
Their finding? While it may be wildly unpleasant, diarrhea may actually serve a vital function in your body by helping it clear out illnesses that are making you sick.
First, some basics: Diarrhea happens when you get extra water in your poop. Your intestinal wall is lined with cells that allow some water to enter the digestive process but, when you’re sick, more water than usual seeps in. Thus, diarrhea.
So, in a new study published in the journal Cell Host & Microbe, researchers made mice sick with bugs that messed up their intestines to try to figure out why this happens. Here’s what they found: When the mice became sick, their immune cells travelled to the wall of their intestines and released a protein called interleukin-22. The protein then bound itself to the cells on the intestines and prompted them to release another protein called claudin-2, which started a leak where the cells meet, allowing more water in. Thus, mice diarrhea.
The study’s researchers compared different types of mice that they had genetically engineered and found that those that made a lot of claudin-2 always had diarrhea (even when they were healthy), while regular mice only got it when they were sick. So, claudin-2 seems to be an important part of the equation.
Of course, this is a study on mice—not humans—and while human bodies produce interleukin-22 and claudin-2 as well, it’s hard to know if the mechanics are the same for people unless it’s tested first.