Have you ever noticed your stool doing a little bob on the surface of the toilet water, while other times it sinks straight to the bottom? This common occurrence, whether your poop is a floater or a sinker, isn’t just a bathroom quirk; it can actually offer insights into the bustling world of bacteria within your gut.
Before we delve into the science, consider this question posed by Nagarajan Kannan: “Are you a floater or a sinker?” It might seem like an overly personal question for a casual acquaintance, but for Kannan, director of the Mayo Clinic’s stem cell and cancer biology lab, it’s a question that sparked a fascinating side project. While his primary research focuses on the complexities of breast cancer at a cellular and molecular level, Kannan has become intrigued by a more everyday enigma – why faeces sometimes float.
Most people have experienced the phenomenon: the unmistakable floater, stubbornly resisting the flush, drifting on the water’s surface. Conversely, other bowel movements disappear without a trace, sinking rapidly. What dictates this difference? Kannan believes the answer to this scatological puzzle reveals surprising details about our internal processes and the health of our gut microbiome.
Initial theories suggested that fat content was the culprit behind floating faeces. However, in the early 1970s, two curious gastroenterologists at the University of Minnesota embarked on a series of experiments to investigate this. By meticulously analyzing excrement from 39 volunteers, including their own contributions, they discovered that gas, not fat, was the key factor determining buoyancy.
The amount of gas present in stool varies significantly, causing it to either float or sink. The researchers found that if the gas was removed from a floating stool, it would sink. The initial conclusion pointed towards excessive methane production, or in simpler terms, too much flatulence, as the reason for floaters.
But the story doesn’t end there. In the years since, medical science has increasingly highlighted the profound impact of our gut microbiota on numerous aspects of our health, ranging from obesity to heart disease. Kannan hypothesized that the composition of the trillions of bacteria, fungi, and other microorganisms residing in our guts might be the deciding factor in whether our faeces are buoyant.
“The majority of faecal matter primarily comprises transformed food particles forming a bacterial mass,” Kannan explains.
To test this theory, Kannan and his team at the Mayo Clinic conducted a study using mice raised in germ-free environments. These mice lacked any microbes in their guts. In faecal floatation tests, the poop from these germ-free mice sank immediately. In contrast, approximately 50% of the droppings from mice with normal gut microbes floated, before eventually sinking. Upon closer examination, the reason for this difference became apparent.
“Germ-free faeces are packed with sub-microscopic undigested food particles and have a higher faecal density than microbially loaded faeces,” says Kannan. To further solidify their findings, the team performed faecal transplants. They introduced gut bacteria from normal mice (whose poop floated) into the germ-free mice. Remarkably, the formerly germ-free mice then began to produce droppings that also floated.
Intriguingly, when the mice received bacteria from human donors, their stool also floated. “It seems that once those microbes set up shop, it’s a universal ‘rise to the top’ situation for mouse poop, regardless of the donor species,” Kannan notes.
The researchers also conducted comprehensive genetic analyses of the bacterial species present in the floating mouse poop. They discovered elevated levels of ten bacterial species known to produce gas. Bacteroides ovatus emerged as a dominant species, recognized for its gas production through carbohydrate fermentation and previously linked to excessive flatulence in humans.
While these findings in mice provide valuable insights, it’s important to note that they need to be confirmed for human “floaters” and “sinkers.” Nevertheless, Kannan suggests that the buoyancy of our poop could serve as an indicator of shifts in the bacterial communities within our guts.
“I have this inkling that a ‘floater’ might transiently become a ‘sinker’ while on antibiotics,” he speculates, though he acknowledges the lack of research in this specific area. “Securing funding for faecal floatation isn’t a walk in the park, unfortunately.”
Numerous factors can influence the composition of our gut bacteria, including our diet, smoking habits, stress levels, and various medications. Kannan is now eager to explore the specific conditions that promote the flourishing of gas-producing bacteria.
“Whether you’re at a packed social event or on a deep space journey, you probably don’t fancy being seated next to someone with a gut full of these gasogenic microbes and a penchant for frequent flatulence.”
It might be a somewhat undignified area of scientific inquiry, but understanding why our poop floats holds potential clues to our gut health and the complex world within.
