‘Smart underwear’ could help unlock secrets of human flatulence

By Claire Cameron edited by Tanya Lewis

Whether you’re breaking wind, farting hard or just letting out a quick toot, flatulence is—whether you want to admit it or not—as much a daily necessity as breathing. But exactly how often the average person lets one rip and what that says about their body is something of a mystery.

“We don’t actually know what normal flatus production looks like,” said Brantley Hall, an assistant professor at the University of Maryland, in a statement. (Flatus is the technical term for a fart.) “Without that baseline, it’s hard to know when someone’s gas production is truly excessive,” he added.

Smart Underwear, a wearable device co-created by Hall and his colleagues, could help provide an answer to the pungent question.

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The wearable isn’t truly underwear but rather a device that snaps on to garments and uses chemical sensors to track intestinal gas, especially hydrogen, which is produced by microorganisms in the gut. Typically, farts are a mix of microbe-derived hydrogen and occasionally methane, as well as carbon dioxide and oxygen produced by the body.

In a study of the device, Hall and his team found that healthy adults fart some 32 times a day—although some tooted a mere four times, while others passed wind 59 times in a day. The study did not measure whether the farts were smelly or audible, however.

Hall and his team tested the device on 38 healthy adults, who all wore it in their underwear for a week while they were awake, except when they were engaged in heavy exercise or traveling. The participants followed a special low-fiber diet, although half were given fiber supplements partway through the study—making them produce more hydrogen gas—to see if the Smart Underwear could tell the difference. As hoped, the Smart Underwear detected the heightened microbiome activity in the presence of fiber, according to a paper describing the study, which was published in Biosensors and Bioelectronics: X.

The range in daily fart frequency challenges “the assumption that a median amount of flatus per day can adequately describe human physiology,” Hall and his co-authors write in the paper. Knowing how much the average person farts can help inform treatments for people who experience excessive flatulence or other problems.

The Smart Underwear is just a first step. Hall also launched the Human Flatus Atlas to recruit and measure flatulence across the population. In particular, the researchers are interested in studying people who eat high-fiber diets but don’t fart much and people who fart a lot.

“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 in the statement. The Human Flatus Atlas could help establish a population-wide baseline for flatulence. And that, in turn, could help researchers develop better treatments for gut health.

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