Scientists have created smart underwear that can track how often a person farts, potentially offering new insights into digestion and metabolism. Until now, researchers have relied on self-reported data, which can be unreliable because people often forget or miscount their gas emissions. Earlier attempts at direct measurement involved uncomfortable rectal tubes, which were impractical for long-term studies. Now, a new non-invasive method has been developed using wearable sensors that are both comfortable and capable of continuous monitoring. The smart underwear works by tracking the release of hydrogen gas, which is produced by the gut microbiome during the digestion of food. A small, discreet device attaches to the underwear and uses sensors to monitor hydrogen levels continuously. In a study published in the journal Biosensors and Bioelectronics, nearly 60 healthy participants tested the device. Nineteen wore the underwear for seven days during normal daily activities to assess comfort and continuous monitoring. Another 38 participated in a controlled diet study to see if the device could detect changes in gas production caused by different foods. The study found that healthy adults typically pass gas an average of 32 times a day, significantly higher than the 14 times often cited in medical literature. Individual variation was wide, ranging from as few as four farts to as many as 59. The device specifically tracks hydrogen, which is a key component of flatulence. Most farts contain hydrogen, carbon dioxide, and nitrogen, with some people also producing methane. Because hydrogen is made only by gut microbes, tracking it provides a clear indication of how actively the microbes are fermenting food in the intestines. Researchers plan to expand the study by using the smart underwear to track flatulence patterns in hundreds of people over time. They aim to correlate these patterns with diet and the composition of the gut microbiome. Establishing objective baselines for microbial activity is crucial for understanding how changes in diet, probiotics, or prebiotics affect gut health. This research could lead to better diagnostic tools and more effective treatments for digestive disorders.