What Changes in the Gut Microbiome Occur at the Onset of Inflammatory Bowel Disease? At the onset of inflammatory bowel disease, the gut microbiome shows a clear loss of beneficial, obligate anaerobic bacteria that help digest complex carbohydrates, and a rise in oxygen-tolerant bacteria, including species that normally live in the mouth. These shifts were detected in newly diagnosed people with Crohn’s disease and ulcerative colitis before any treatment, across a combined dataset of more than 1,700 participants from 11 countries.

At IBD onset, helpful anaerobes fade while oxygen-tolerant microbes surge—reshaping the gut ecosystem. Could early interventions target this shift? #CrohnsDisease #InflammatoryBowelDisease #Microbiome #OxygenHypothesis #UlcerativeColitis