Yesterday was International IBD Day. And whether you live with Crohn's disease or ulcerative colitis, love someone who does, or have simply spent years being told your gut symptoms are "normal," this day is worth a moment of your attention.
IBD (inflammatory bowel disease) affects an estimated 6.8 million people worldwide [1]. That's not a rare condition. That's multiple stadiums worth of people navigating something that most of us have never been taught to talk about.
The most useful thing we can do is look at what the science actually suggests. Because the research into IBD and the gut microbiome is pointing somewhere genuinely significant, and it matters not just for people with IBD, but for all of us who are paying attention to gut health.
What IBD Actually Is (and Why the Gut Microbiome Is Central to It)
IBD is an umbrella term for two chronic inflammatory conditions of the digestive tract: Crohn's disease, which may affect any part of the gastrointestinal system, and ulcerative colitis, which is primarily associated with the colon and rectum. Both involve chronic inflammation, and both appear to have a complex relationship with the gut microbiome.
Research published in Nature Reviews Gastroenterology and Hepatology found that IBD is not simply a genetic condition. Environmental factors, including diet, early-life exposures, and gut microbiome composition, appear to play a significant role in who develops IBD and how severe it becomes [2].
The gut microbiome -- the vast community of bacteria, fungi, and other microorganisms living in the digestive tract -- seems to be one of the most important variables in this picture. And the relationship between the microbiome and IBD is not straightforward: it appears to be bidirectional, meaning the microbiome may influence IBD, and IBD may influence the microbiome.
What Research Suggests About the Gut Microbiome in IBD
One of the most consistent findings in IBD research is the apparent reduction in gut microbiome diversity among people with the condition.
Research published in PNAS in 2007 was among the first to characterise the microbial community imbalances in human IBD in detail. The study found that people with Crohn's disease and ulcerative colitis showed significantly reduced gut microbiome diversity compared to healthy controls, with notable reductions in bacteria from the Firmicutes and Bacteroidetes groups [3].
This finding has since been replicated and expanded. Research published in Nature Microbiology in 2017 followed people with IBD over time and found that gut microbiome instability -- meaning a microbiome that shifts unpredictably rather than holding a steady, diverse state -- appeared to be a consistent feature of active IBD. The researchers found that this instability was more pronounced in people with Crohn's disease than ulcerative colitis, and suggested it may be a useful marker for understanding disease activity [4].
Further research published in Gastroenterology in 2017 reviewed the role of intestinal bacteria in IBD pathogenesis and found that while cause and effect are complex and not fully understood, evidence suggests gut microbial imbalance (sometimes called dysbiosis) appears to be both a feature and a potential contributing factor in IBD [5].
None of this means the microbiome is the whole story. IBD is a complex condition with genetic, immunological, and environmental components. But it does suggest that the gut microbiome is a meaningful piece of the puzzle.
Why This Matters Beyond IBD
Here is the part that we want every person reading this to sit with for a moment.
The research into IBD and the gut microbiome has, somewhat indirectly, illuminated something much broader: gut microbiome diversity appears to matter. Not just for people with a diagnosis, but for everyone who has a gut, which is all of us.
When researchers study what the microbiome looks like in IBD and compare it to what it looks like in people without IBD, they are telling us something about the characteristics of a gut ecosystem that appears to be under strain versus one that appears to be in a more stable state. Lower diversity, less stability, greater fluctuation: these are patterns that keep showing up in gut health research far beyond IBD.
For women, especially those in perimenopause and menopause, the gut microbiome shifts significantly alongside changing hormone levels. Symptoms like bloating, constipation, abdominal discomfort, and irregular digestion are among the most commonly reported gut symptoms during this period. They are not IBD. But they are a signal that something in the gut environment is changing, and that paying attention to those patterns may be worth doing.
International IBD Day is a reminder that the gut is not a background organ. For millions of people, it is the site of daily struggle. For the rest of us, it is still one of the most under-monitored, under-discussed systems in the body.
A Note on IBD Specifically
If you have IBD, or suspect you might, please speak to your GP or gastroenterologist. IBD is a diagnosed medical condition that requires clinical care and monitoring. Nothing in this post replaces that.
This post is written in the spirit of awareness: for the 6.8 million people living with IBD globally [1], for the many more whose gut symptoms have never been properly investigated, and for everyone who thinks the gut deserves more of our collective attention.
Today of all days, it does.
This content is for informational purposes only and does not constitute medical advice. If you have concerns about your digestive health, please speak to a healthcare professional.
References
1. GBD 2017 Inflammatory Bowel Disease Collaborators. (2020). The global, regional, and national burden of inflammatory bowel disease in 195 countries and territories, 1990--2017. The Lancet Gastroenterology and Hepatology, 5(1), 17--30. https://doi.org/10.1016/S2468-1253(19)30333-4
2. Ananthakrishnan, A. N. (2015). Epidemiology and risk factors for IBD. Nature Reviews Gastroenterology and Hepatology, 12(4), 205--217. https://doi.org/10.1038/nrgastro.2015.34
3. Frank, D. N., et al. (2007). Molecular-phylogenetic characterization of microbial community imbalances in human inflammatory bowel diseases. Proceedings of the National Academy of Sciences (PNAS), 104(34), 13780--13785. https://doi.org/10.1073/pnas.0706625104
4. Halfvarson, J., et al. (2017). Dynamics of the human gut microbiota in inflammatory bowel disease. Nature Microbiology, 2, 17004. https://doi.org/10.1038/nmicrobiol.2017.4
5.Sartor, R. B., & Wu, G. D. (2017). Roles for intestinal bacteria, viruses, and fungi in pathogenesis of inflammatory bowel diseases and therapeutic approaches. Gastroenterology, 152(2), 327--339. https://doi.org/10.1053/j.gastro.2016.10.012
