How often do people really fart? Scientists built smart underwear to find out

UNITED STATES, March 21 — Researchers at the University of Maryland have developed Smart Underwear, the first wearable device designed specifically to measure human flatulence. The small sensor tracks hydrogen in flatus, allowing scientists to reexamine long held assumptions about how often people pass gas. The technology also offers a new way to observe gut microbial metabolism during everyday life.

For many years, doctors have had limited tools to evaluate patients who report problems with intestinal gas. Gastroenterologist Michael Levitt, widely known in the field as the "King of Farts," highlighted the challenge in 2000 when he wrote: "It is virtually impossible for the physician to objectively document the existence of excessive gas using currently available tests."

To tackle this issue, a research group led by Brantley Hall, an assistant professor in the Department of Cell Biology and Molecular Genetics at UMD, created Smart Underwear, a compact wearable device that clips discreetly onto regular underwear. The device contains electrochemical sensors that continuously monitor intestinal gas production throughout the day and night.

In research published in Biosensors and Bioelectronics: X , a study led by UMD assistant research scientist Santiago Botasini used the device to measure flatulence in healthy adults. Participants produced flatus an average of 32 times per day, about twice the 14 ( 6) daily events often cited in earlier medical literature. However, results varied widely among individuals, with totals ranging from just four flatus events per day to as many as 59.

Older estimates were likely lower because previous studies depended on invasive measurement techniques conducted in small groups or relied on self reporting. Both approaches can miss events, depend on imperfect memory, and cannot record gas production while someone is asleep. In addition, people differ significantly in visceral sensitivity, meaning two individuals may produce similar amounts of flatus yet perceive it very differently.

"Objective measurement gives us an opportunity to increase scientific rigor in an area that's been difficult to study," said Hall, the study's senior author.

In most people, flatus is composed primarily of hydrogen, carbon dioxide and nitrogen. Some individuals also produce methane. Hydrogen is generated exclusively by microbes living in the gut, so continuously measuring hydrogen in flatus provides a direct signal of microbial fermentation activity as gut bacteria break down food components.

"Think of it like a continuous glucose monitor, but for intestinal gas," Hall said, explaining that the device detected increased hydrogen production after participants consumed inulin, a prebiotic fiber. The sensor identified these increases with 94.7% sensitivity.

Scientists have established normal ranges for many health measures such as blood glucose and cholesterol. For flatulence, however, there is no widely accepted 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 gap, Hall's laboratory is launching a large project called the Human Flatus Atlas. The study will use Smart Underwear to measure flatulence patterns continuously in hundreds of participants while also analyzing their diets and gut microbiome composition. Devices will be shipped directly to volunteers, allowing adults across the United States to participate from home. The goal is to determine the normal range of flatus production among people in the United States over the age of 18.

To capture the full spectrum of variation, researchers are recruiting volunteers who fit several categories identified during early research. Zen Digesters are people who eat high fiber diets (25-38 grams of fiber daily) but produce very little flatus. Studying them may help researchers understand how the microbiome adapts to diets rich in fiber. Hydrogen Hyperproducers are individuals who pass gas frequently. Examining this group may reveal biological factors that drive high gas production. Normal People represent those who fall between these two extremes.

To better understand the microbes responsible for these differences, the team will collect stool samples from Zen Digesters and Hydrogen Hyperproducers 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."

People interested in participating can learn more at flatus.info. Enrollment is open to adults ages 18 years or older in the U.S. Participants will receive a Smart Underwear device and will wear it both day and night during the study period. Enrollment is limited.