JMIR Publications

ABSTRACT

Continuous monitoring of intestinal gas production in natural home settings remains technically challenging, yet offers unique potential for personalized gastrointestinal health tracking. We developed a digital toilet system with gas sensors (MQ-4, MQ-136) and iOS app enabling continuous monitoring of relative CH₄ and H₂S production normalized to individual baselines (R0 calibration). In a 99-day intensive study of a married couple (one male, one female, middle-aged) sharing the same household, meals, and daily routines, we integrated gas monitoring with stool form assessment (Bristol Stool Scale), dietary logging, and bi-weekly gut microbiome profiling (16S rRNA sequencing). This cohabiting design was conducted under shared environmental conditions, allowing evaluation of whether the system could detect individual-specific biological differences within a naturally shared living context. Despite 99 days of shared living conditions, the two individuals maintained profoundly distinct metabolic signatures. CH₄ remained at low baseline in both subjects, but the male subject showed sporadic 300-fold spikes versus stable patterns in the female subject. H₂S demonstrated consistent 10-15× higher baseline in the male subject. Even with shared meals, individual dietary choices differed: protein-dominance in the male subject (44.4%) versus carbohydrate-dominance in the female subject (32.3%), with strong CH₄-dairy/dessert correlation (r=0.889). Most remarkably, gut microbiome composition remained completely separated throughout the study (PERMANOVA p<0.01): Prevotella-dominant in the male subject (46.58%) versus Bacteroides/Bifidobacterium-enriched in the female subject (26.25%/17.13%), representing a 463-fold difference. Gas-microbiome correlation networks also diverged, with the female subject showing ultra-high CH₄ correlations (r>0.9 for 8 genera) while the male subject exhibited denser, moderate networks. This study demonstrates that individual metabolic signatures persist despite shared environment, validating the biological necessity of personalized monitoring. Our platform successfully distinguished true biological variation from environmental variability within a shared real-world household context.The intensive longitudinal design provides a scalable foundation for precision gastroenterology, N-of-1 trials, and early disease detection through personalized baseline tracking.