Why Do Some Poops Float While Others Sink? A Scientific Inquiry
Written on
Understanding the Phenomenon of Floating and Sinking Poop
As the holiday season approaches, bringing with it a feast of culinary delights, it’s the perfect time to ponder a topic that piqued our curiosity as children: why do some stools float while others sink? This question, once a source of embarrassment at family gatherings, is rooted in science.
In the past, particularly during the late Pleistocene era, medical professionals believed that the fat content in meals was the main factor influencing stool buoyancy. However, recent research indicates that this may not be the only explanation for floating stools in healthy individuals. It’s essential to note that conditions like gastrointestinal infections or pancreatitis, which impair fat digestion and absorption, can indeed result in floating stools.
The Role of Gas in Stool Buoyancy
Your childhood intuition may be on point; the ability of stools to float is closely linked to the presence of gas. Essentially, gas bubbles trapped in the stool are responsible for this phenomenon. This raises a further question: why do some individuals experience more gas than others?
A group of researchers stumbled upon the answers to these intriguing questions while investigating a different aspect of gut health. They were examining the gut microbiomes of laboratory mice to determine how specific bacterial species influenced digestion and health. Some mice had their gut flora sterilized, while others were allowed to maintain their natural microbiome.
During their experiments, the scientists observed that the sterilized mice consistently produced sinking stools, while about 50% of the stools from the normal mice floated.
The Impact of Gut Bacteria
This unexpected finding led the researchers to hypothesize that the gut's bacterial community is responsible for the buoyancy of stools. To test this theory, they collected floating stools from healthy mice not involved in the study and introduced these samples into the sterilized mice. (The method of introduction, as you might imagine, is best left to the imagination.)
After reintroducing normal stool samples into the sterilized mice, these subjects began producing floating stools. This pivotal discovery suggested that the gut microbiota is crucial in generating floating stools, as certain bacterial species produce more gas than others.
To further clarify this relationship, the researchers attempted to identify which specific bacterial species were responsible for gas production but found it challenging. They discovered over ten gas-producing bacterial species within the typical gut microbiome. Notably, Bacteroides ovatus, a prevalent anaerobic bacterium, was linked to increased flatulence and intestinal disorders when it proliferates excessively.
Source: Syed Mohammed Musheer Aalam, Daphne Norma Crasta, Pooja Roy, A. Lee Miller II, Scott I. Gamb, Stephen Johnson, Lisa M. Till, Jun Chen, Purna Kashyap & Nagarajan Kannan (2022). Genesis of fecal floatation is causally linked to gut microbial colonization in mice, Scientific Reports | doi:10.1038/s41598–022–22626-x
Keep updated with my writing by subscribing to my free newsletter.