Scientists Accidentally Reveal Why Some Feces Float and Others Sink

In a new chapter of unsolved mysteries, by accident, a group of scientists revealed why some feces float and others simply sinkone of the many questions that we have ever asked ourselves and that has been answered in a study published in IFL Science.

As you recall the report published on the website of gizmodoscience tried to clarify this in 1972 through research published in The New England Journal of Medicinein which they analyzed the feces of 33 healthy subjects, nine floating24 who sank and six patients with “greasy” stools.

That study found that those that sank did so when the gas within the feces was “compressed by positive pressure.”

After outgassing, feces that previously floated and sank had similar specific gravities, indicating that the floating or sinking propensity of such feces depends on differences in gas rather than fat content. Thus, the feces float due to increased gas or water content (or both); floating stools should not be considered a sign of steatorrhea,” they detailed at the time.

Now this new research resolves the difference in gas and water content. The experts used mice that had been bred to be germ-free and noted that their poop was unusual.

The study of “flying” feces

While about 10 percent of healthy humans consistently produce “flying” stool, this percentage is much higher in mice, at about 50%.


The researchers found that mouse poop tended to sink: “Our serendipitous finding of ‘sinking’ and ‘floating’ feces in germ-free and gut-colonized mice, respectively, led to the question of whether gut colonizers were fundamentally linked to the genesis of the fecal floating phenomenon.”

To confirm this, they analyzed intestinal bacteria from healthy mice and put them into the stomachs of germ-free mice. Sure enough, their poop began to float.

“By introducing microorganisms into the gut of germ-free mice, we have conclusively shown that gut microbiota colonization is a prerequisite for feces to float.”

Leave a Comment