Researchers have created "Smart Underwear," a wearable device that measures flatulence by detecting hydrogen produced by gut microbes. The innovation represents a significant shift in how scientists can study what has long been one of the most difficult bodily functions to measure objectively. For decades, medical professionals have struggled with this challenge: a patient complains of excessive gas, but the doctor has no reliable way to verify the claim.
Researchers led by Brantley Hall, an assistant professor in the Department of Cell Biology and Molecular Genetics at the University of Maryland, developed the device, which snaps discreetly onto any underwear and uses electrochemical sensors to track intestinal gas production around the clock. The device is elegantly simple in its design. It listens for a chemical signature: hydrogen released when microbes ferment carbohydrates in the gut. This continuous monitoring produces a record of intestinal activity impossible to obtain through other methods.
What the researchers discovered upended conventional medical wisdom. Participants produced flatus an average of 32 times per day, about twice the 14 (±6) daily events often cited in earlier medical literature. Yet the variation between individuals was enormous. Results ranged from just four flatus events per day to as many as 59.
Why was the older estimate so far off the mark? Previous research relied on invasive techniques in small studies or self-reporting, which suffers from missed events, imperfect memory and the impossibility of logging gas while asleep. The fundamental problem is one of measurement error. When you ask people to keep a diary of their own emissions, you are asking them to notice something they may not perceive, remember it accurately, and record it consistently over days. People miss events, particularly during sleep. They also may undercount simply because they do not always notice, or they may feel embarrassed and consciously minimise what they report.
The research has implications beyond settling a point of scientific curiosity. There is no widely accepted baseline for flatulence, and without that baseline, it's hard to know when someone's gas production is truly excessive. Doctors treating patients with irritable bowel syndrome, food intolerances, or other gastrointestinal disorders often rely on subjective descriptions of symptoms. If a patient says they have excessive gas, the doctor can offer symptomatic treatment, but without an objective measure of what normal looks like, clinical assessment remains imprecise.
The device detected increased hydrogen production after participants consumed inulin, a prebiotic fibre, with 94.7% sensitivity. This suggests the technology can reliably track how diet influences gas production and how the gut microbiome responds to dietary changes. That capability opens new research pathways for understanding how probiotic and prebiotic interventions affect digestive health.
The research team is now launching a broader study called the Human Flatus Atlas, which will use Smart Underwear to measure flatulence patterns continuously in hundreds of participants while also analysing their diets and gut microbiome composition. The team will collect stool samples from Zen Digesters and Hydrogen Hyperproducers for microbiome analysis. These are two extremes the researchers identified: people who eat high-fibre diets yet produce minimal gas, and people who produce far more gas than typical. By studying what is different about their microbiomes, scientists may understand the biological factors that drive variation in gas production.
For consumers and patients, the practical value is straightforward. Objective measurement offers reassurance: a person can know whether their perceived excess gas is genuinely excessive or simply their perception. For researchers and clinicians, it offers a foundation for future diagnostics. Scientists have learned much about which microbes live in the gut, but less about what they're actually doing at any given moment; 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.