Smart underwear: A novel wearable for long-term monitoring of gut microbial gas production via flatus

The temporal dynamics of gut microbial metabolism, including how quickly and variably microbes respond to dietary changes, remain largely invisible to current research methods. While measuring metabolic outputs like short-chain fatty acids (SCFAs) in stool or blood provide insights into microbial metabolism, sampling frequency is severely limited, preventing observation of the temporal dynamics of how gut microbes respond to dietary inputs and environmental changes on an hour-by-hour basis. Hydrogen gas, produced by gut microbial metabolism, represents an underutilized biomarker for continuous monitoring of microbial metabolic activity. Following its production, hydrogen is expelled through two major routes: breath and flatus, with flatus containing dramatically higher hydrogen concentrations compared to breath, making it an ideal target for sensitive detection. Currently, no tools exist for continuous, non-invasive monitoring of hydrogen in flatus to track changes in gut microbial metabolism. To address this gap, we developed the Smart Underwear, the first wearable device that continuously measures hydrogen gas expelled in flatus, providing unprecedented temporal resolution of gut microbial activity. In a week-long User Experience Study, the Smart Underwear successfully tracked hydrogen in flatus with participants reporting high comfort and compliance. In a second study, the Smart Underwear accurately detected increased hydrogen production following inulin ingestion with 94.7 % sensitivity in 38 healthy participants, demonstrating its capability to track diet-induced changes in microbial metabolism. This novel platform enables longitudinal studies of microbiome function, capturing both inter-individual differences and intra-individual temporal dynamics, while opening new avenues for investigating diet-microbiome interactions, circadian patterns, and the functional consequences of changes in microbial composition. • The Smart Underwear is the first wearable for monitoring gut microbiome activity via flatus hydrogen. • Participants wore the Smart Underwear >11 hours/day with high adherence to the study protocol and rarely reported discomfort. • Validated detection of diet-driven shifts in gut microbial activity via the Smart Underwear with 94.7% sensitivity. • The Smart Underwear enables novel longitudinal studies of gut microbial metabolism.