Passing wind and the complaint of “too much gas” are not quite the same, yet both have baffled clinicians for years. The topic is uncomfortable, an easy punchline, and typically avoided in polite chat.
Even so, each fart is a recordable biological moment, influenced by the trillions of microbes that inhabit the human gut.
Researchers have now developed something that has not previously existed: a practical way to measure those moments accurately in everyday life, continuously throughout the day.
How Smart Underwear works
A research group at the University of Maryland (UMD) has produced Smart Underwear, described as the first wearable built to measure human flatulence.
The device attaches discreetly to ordinary underwear and relies on electrochemical sensors to monitor intestinal gas 24/7. In particular, it measures hydrogen in flatus.
Hydrogen is important because gut microbes generate it when they ferment certain foods-especially fibres the body cannot digest by itself. As a result, hydrogen levels provide a direct window into what the microbiome is doing inside the body.
For decades, doctors have had difficulty supporting patients who say they have excessive gas. The issue was never a lack of interest; it was the absence of suitable measurement tools.
As gastroenterologist Michael Levitt-well known in the field as the “King of Farts”-put it: “It is virtually impossible for the physician to objectively document the existence of excessive gas using currently available tests.” That limitation helped motivate a different strategy.
A surprising number of daily farts
To evaluate the device, a team led by UMD assistant research scientist Santiago Botasini trialled it with healthy adults. The outcomes surprised even experienced investigators.
On average, participants passed flatus 32 times a day-more than twice the 14 daily events often cited in medical literature. At the low end, some people passed wind only four times per day; at the high end, others reached 59.
Earlier estimates were probably low for straightforward reasons. Many studies depended on self-reporting: people forget, miss episodes, and are unlikely to record gas during sleep.
Other studies used invasive approaches and included only small numbers of volunteers. There is also the fact that gas is felt differently from person to person-two people may produce similar amounts, yet experience them very differently.
Brantley Hall, an assistant professor in UMD’s Department of Cell Biology and Molecular Genetics, served as the study’s senior author and led the work to develop the device.
“Objective measurement gives us an opportunity to increase scientific rigor in an area that’s been difficult to study,” said Hall.
What farts reveals about the gut
Flatus is typically a mixture of hydrogen, carbon dioxide, and nitrogen. Some individuals also generate methane. Hydrogen is distinctive because it is produced only by gut microbes-human cells do not make it.
By monitoring hydrogen continuously, Smart Underwear provides an ongoing read-out of microbial fermentation. When particular fibres are eaten, microbes ferment them and release hydrogen as a byproduct, and the device can pick up that shift.
“Think of it like a continuous glucose monitor, but for intestinal gas,” Hall said, adding that the device detected increased hydrogen production after consumption of inulin, a prebiotic fibre, with 94.7 percent sensitivity.
That level of sensitivity is significant. The microbiome is now a major area in health research, and scientists have already catalogued which microbes live in the gut.
However, it has been much harder to determine what those microbes are doing in real time. Intestinal gas may be one of the most direct signals available.
Defining “normal” gas levels
Clinicians have well-established normal ranges for blood pressure, cholesterol, and blood sugar. For flatulence, there is no agreed baseline.
“We don’t actually know what normal flatus production looks like,” Hall said. “Without that baseline, it’s hard to know when someone’s gas production is truly excessive.”
To address this, Hall’s lab is starting the Human Flatus Atlas. Using Smart Underwear, the project will track flatulence patterns day and night in hundreds of adults across the United States.
People can take part remotely, with devices posted directly to their homes.
The researchers will then compare gas patterns with diet and microbiome composition, aiming to define what is typical among adults over 18 in the U.S.
Mapping digestive extremes
Early findings already point to notable extremes. Some individuals eat high-fibre diets-around 25 to 38 grams of fibre per day-yet report very little flatus.
The team refers to these people as Zen Digesters. At the other end are those who produce large amounts of hydrogen and pass wind often; these Hydrogen Hyperproducers could help explain why some digestive systems are more active than others.
To explore this further, the researchers will collect stool samples from people at both ends of the spectrum for microbiome analysis.
“We’ve learned a tremendous amount about which microbes live in the gut, but less about what they’re actually doing at any given moment,” Hall said.
“The Human Flatus Atlas will establish objective baselines for gut microbial fermentation, which is essential groundwork for evaluating how dietary, probiotic or prebiotic interventions change microbiome activity.”
Smart underwear and human health
Gas is a normal part of digestion. Still, for some people it brings genuine discomfort, embarrassment, and anxiety. Without robust data, doctors have often had little to offer beyond reassurance.
Objective measurement could change that. Researchers may finally be able to compare an individual’s gas production against a meaningful baseline.
They can also assess how particular foods, fibres, or supplements influence microbial activity. Over time, this could support more personalised guidance on diet and gut health.
The idea may sound comical at first-Smart Underwear, a flatus atlas-but the humour masks a serious change.
For the first time, researchers can measure one of the most common human experiences precisely, and sometimes progress begins in the most unexpected places.
The complete study appeared in Biosensors and Bioelectronics.
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