An unspeakable question: Why does my poop always float?

After releasing yourself in the bathroom, do you look back at the ups and downs in the toilet bowl?

Most of the time, people's feces will sink quietly in the water - however, a few people will find that their feces float on the water, and it is said that this situation accounts for 10%-15% of the population.

Why does poop float? Is it a sign of some disease?

Why does feces float on water?

This may be a difficult question, but scientists have actually conducted serious research on it. As early as 1972, a paper titled "Floating Feces - Gas or Fat" was published, and it was even published in the famous New England Journal of Medicine [1].

The fact that feces float on water means that they must contain some components with a lower density than water. In the past, people speculated that these low-density components could be fat or gas - and this study confirms that the latter is generally the correct answer. In other words, feces float because they contain more gas.

The researchers collected fresh fecal samples from 33 healthy volunteers for the study, of whom 9 always pulled out floating feces, while the feces of the remaining 24 always sank. The researchers cut the samples into small pieces with a thread, carefully dropped them into 25°C distilled water, observed their sinking and floating states, and then analyzed the differences in their components.

They found that the floating samples always contained more gas, and their fat content was not significantly different from those that sank. If the gas inside the sample was completely removed by vacuuming, the density of the floating and sinking samples would become basically the same.

Who inflated the poop?

The gases in the feces are produced by intestinal bacteria. They metabolize food residues that are not digested and absorbed by humans, and can produce gases such as hydrogen, methane, carbon dioxide, and hydrogen sulfide. Individual differences in intestinal flora lead to differences in the amount of gas produced, which also leads to differences in the sinking and floating of feces.

Another recently published study in mice demonstrated that changes in the gut microbiota can directly affect the sinking and buoyancy properties of feces. The researchers accidentally discovered that after the germ-free mice were given gut bacteria, their feces became less dense and more likely to float in the fixative solution used to process the samples [2].

Different bacteria contribute differently to gas production. Through metagenomic analysis, this study found that the species that "gases" the most feces is Bacteroides ovatus - of course, this is just an animal experiment, and whether the conclusions are applicable to humans needs further verification.

In addition to differences in bacterial flora, factors such as diet (such as the fiber content of food) can also affect the amount of gas produced.

Is it a disease if poop floats?

Some abnormal conditions do make stool more floatable, such as steatorrhea due to poor nutrient absorption or certain intestinal infections. These conditions often also cause other changes in stool characteristics and intestinal symptoms.

If it's just floating stool and nothing else is unusual, then there's generally no need to worry.

References
[1]https://www.nejm.org/doi/full/10.1056/NEJM197205042861804
[2]https://www.nature.com/articles/s41598-022-22626-x

Author: Window Knocking Rain

Editor: odette

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