The mystery of why our number twos sometimes rise to the surface of toilet water while others sink without a trace has been solved – and it could be a window into the health of the bacteria living in our guts .
Before we dive in, Nagarajan Kannan has a question: “Are you a floater or a sinker?” “It’s a surprisingly intimate thing to ask someone you’ve only exchanged emails with, but it’s exactly this line of thinking that led to a somewhat exciting project for the stem cell lab director and in Cancer Biology from the Mayo Clinic in Rochester, Minnesota. .
Most of her daily work is devoted to studying the cellular and molecular mechanisms that lead to breast cancer. But during rare moments of inactivity, Kannan found himself grappling with another conundrum: why feces sometimes float.
Most of us have probably experienced it at some point: the poop that simply refuses to empty, bobbing on the surface of the water like an incriminating brown buoyancy aid. At other times, however, our number twos simply sink without a trace. A mystery indeed.
The answer to this scatological riddle, however, offers surprising insights into what’s happening inside our bodies and the health of the microbes that live there, Kannan believes.
It was initially thought that the reason for these occasional unmentionable fluctuations had something to do with the levels of fat that got into it. But in the early 1970s, a few gastroenterologists at the University of Minnesota, with some time on their hands, decided to test it with a series of experiments. After subjecting the feces of 39 volunteers – and some of their own solid waste for good measure – to a series of tests, the answer they came up with was that it was not fat, but gas.
Specifically, the amount of gas found in a stool can vary to such degrees that it can either float on the surface or sink like a brick (with a good portion of the middle of the bowl drifting between the two). If the gas in a float were compressed, the researchers found, they would sink.
The reason for this difference, they concluded, was too much methane production. In other words, excessive flatulence.
And this is where Kannan enters the increasingly fragrant arena. In the years since, medical science has revealed the enormous role our microbiota plays in many aspects of our health – Since obesity to heart disease. Kannan suspected that changes in the composition of the 100 trillion bacteria, fungi, and other microorganisms that inhabit our intestines might be responsible for whether or not our stools are buoyant.
“The majority of fecal matter is essentially made up of processed food particles forming a bacterial mass,” he explains.
To put the theory to the test, he and his colleagues at the Mayo Clinic studied feces from mice raised in sterile conditions. These germ-free rodents have no microbes in their intestines. In the fecal flotation tests developed by the team, the droppings of these mice instantly sank into the water, while about 50% of the feces of mice carrying gut microbes floated, before eventually drifting downward. Upon closer inspection, the reason became clear.
“Germ-free stools are filled with undigested, submicroscopic food particles and have a higher fecal density than microbe-laden stools,” says Kannan. The team then gave some germ-free mice a fecal transplant from normal mice whose feces floated, meaning they received their gut bacteria. The once germ-free mice then also began producing feces that floated.
Even when the mice received bacteria from human donors, they floated, too.
“It appears that once these microbes take hold, it’s a universal ‘rise to the top’ situation for mouse droppings, regardless of the donor species,” says Kannan.
He and his colleagues also conducted a large-scale genetic analysis of the bacterial species found in floating mouse feces and found that they had high levels of 10 bacterial species known to produce gas. The dominant among them was Oval bacteroidswhich is known to produce gases through the fermentation of carbohydrates and has been linked to excessive flatulence in human patients.
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Although the findings in mice should be treated with caution – their relevance to human “floaters” and “sinkers” has not yet been confirmed – Kannan thinks the buoyancy of our droppings could be an indicator of changes in different communities of bacteria in our guts.
“I feel like a ‘floater’ might temporarily become a ‘lead’ while on antibiotics,” he says. But he adds that he hasn’t seen anyone study this yet. “Ensuring funding for fecal flotation is unfortunately not a walk in the park.”
Many factors, including our diet, if we smoke, stress we are under and a wide range of medications we take can all modify the composition of the bacteria present in our intestines. Kannan now wants to explore what leads to the particular flourishing of gas-producing bacteria.
“Whether you’re attending a crowded social event or taking a trip to deep space, you probably won’t like sitting next to someone with a gut full of these gas-producing microbes and a penchant for frequent flatulence. “
It’s a dirty job, but someone has to do it.
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