IBS hasn’t become a different condition. What’s changed is how well we understand it.
Today, IBS is classified as a Disorder of Gut-Brain Interaction (DGBI). That name matters, because it explains why IBS can cause real, sometimes significant symptoms even when your colonoscopy, scans and bloodwork all come back normal. It also explains why treatment usually needs to go beyond changing what you eat.
Rome V, the newest international framework for diagnosing DGBIs, pushes that understanding even further. It comes from the Rome Foundation, the international group of gastroenterologists and gut-brain researchers whose diagnostic criteria the rest of the field builds on, not a single practitioner’s opinion or a trending theory online. So what does it actually mean to call IBS a DGBI?
First, what is a DGBI?
DGBI stands for Disorder of Gut-Brain Interaction. It describes a group of digestive conditions where symptoms come from changes in how the digestive system operates and communicates, rather than from visible structural damage or disease. IBS is the best known of these, alongside chronic upper abdominal discomfort (dyspepsia), chronic constipation, chronic diarrhea, and disorders of bloating and distension.
These conditions can involve several interconnected systems: how the digestive tract moves, how sensitive its nerves are, how the gut and brain communicate, immune and intestinal barrier function, the microbiome, and how the brain processes signals from the gut. The mix looks different from person to person, which is part of why two people can both have IBS and still need very different treatment plans.
IBS is not “all in your head”
This is the misconception worth clearing up first. Calling IBS a Disorder of Gut-Brain Interaction doesn’t mean it’s psychological, or that symptoms are caused by anxiety. The nervous system is part of normal digestive physiology. Your brain and digestive tract are in constant communication through nerves, hormones and immune signals, and that communication regulates digestion, motility, bowel habits, appetite, nausea, and how you experience sensations from your gut.
That communication runs both ways. The brain influences the gut, and the gut influences the brain. When the system becomes dysregulated, digestive symptoms can develop or intensify.
How can IBS cause symptoms when your tests are normal?
This is one of the more confusing parts of an IBS diagnosis. You can have abdominal pain, bloating, constipation, diarrhea or urgency and still have a completely normal colonoscopy, gastroscopy, ultrasound or CT scan. That doesn’t mean nothing is happening.
Most GI investigations are built to find structural disease: inflammation, an ulcer, a tumour, celiac disease, or another condition that could explain your symptoms. DGBIs raise a different question entirely, which is how well the digestive system is working. A colon can look completely normal on a colonoscopy while still having problems with movement, sensitivity, evacuation or gut-brain signalling. The structure can be normal while the process is dysregulated.
Three pieces of IBS: movement, sensitivity and communication
Movement. Your digestive tract is constantly moving, using coordinated muscular contractions to push food, gas and stool through the intestines. When that movement is too slow, too fast or poorly coordinated, symptoms follow. Slow movement tends to show up as constipation, bloating and pressure; faster movement tends to show up as loose stools and urgency. Bowel frequency alone doesn’t tell the whole story either. It’s possible to have a bowel movement every day and still struggle to empty completely, which is why evacuation is such an important part of IBS care.
Sensitivity. The digestive tract has an extensive nerve network, and in IBS those nerves can become more sensitive, a phenomenon called visceral hypersensitivity. Think of it like turning up the volume on a speaker: a normal amount of intestinal stretch, gas or movement that another person barely registers can be experienced as significant pressure, bloating or pain. The sensation is real. What’s different is how strongly the gut and nervous system are detecting and processing that signal.
Communication. Your gut and brain exchange information constantly. Signals from the digestive tract tell the brain what’s happening inside the gut, and signals from the brain influence intestinal movement, secretion and sensation. When that communication becomes dysregulated, factors like stress, poor sleep, illness, or even anticipating symptoms can affect digestion. It’s also why treatments like gut-directed hypnotherapy and GI-focused psychological therapy improve IBS symptoms for many people. These aren’t treatments built on the idea that symptoms are imagined. They target one of the biological systems driving IBS: the gut-brain axis.
Why does someone develop IBS?
There’s no single cause. Genetics, GI infections, motility, visceral hypersensitivity, immune signalling, the microbiome, diet, medications, sleep, hormones, stress and pelvic floor dysfunction can all play a role, in different combinations for different people.
Sometimes there’s a clear starting point, like post-infectious IBS: someone develops gastroenteritis, the infection resolves, but changes in immune signalling, intestinal sensitivity, motility and gut-brain communication persist even after the original trigger is gone. For other people, IBS develops gradually with no single identifiable trigger.
What about bloating?
Bloating is a good example of why the DGBI framework is useful. For years the explanation was simple: bloating meant too much gas. We now know it’s more complicated than that. Bloating can involve fermentation and intestinal contents, but also constipation, altered motility, visceral hypersensitivity, gut-brain signalling, and changes in how the diaphragm and abdominal wall respond to digestive sensations.
Some people with visible abdominal distension experience abdominophrenic dyssynergia, where the diaphragm and abdominal wall respond abnormally as the abdomen distends. This is why someone can become visibly distended without necessarily having an excessive amount of intestinal gas.
Food can trigger IBS without being harmful
People with IBS understandably spend a lot of time thinking about food, but symptoms after eating don’t necessarily mean a food is damaging your digestive system. Eating naturally activates the gut: the stomach stretches, digestive secretions are released, the intestines begin moving, certain carbohydrates get fermented by gut bacteria, and gas and other metabolites are produced. If your digestive system is particularly sensitive, these normal processes can produce real symptoms without any allergy or underlying damage.
Dietary therapy can be genuinely useful for IBS, but the goal shouldn’t be to eliminate more and more foods over time. It should be finding the least restrictive approach that adequately manages symptoms while maintaining good nutrition and food variety.
And the microbiome?
The microbiome is part of the IBS story, but it isn’t the whole story, and it’s also where a lot of confusing marketing happens.
Research does show dysbiosis, an imbalance in gut bacteria, in a large share of people with IBS. But that finding hasn’t translated into a reliable test you can act on. Expert reviews of commercial microbiome testing have found that, given current knowledge and technology, these tests don’t provide much value for clinical decision-making. Major GI societies reflect the same caution: the American Gastroenterological Association’s technical review on IBS with diarrhea doesn’t recommend microbiome analysis, and the Rome Foundation’s own review of the microbiota research stops short of endorsing clinical testing.
Part of the problem is technical. There’s substantial variation from person to person, which makes results difficult to interpret meaningfully. But the bigger issue is what these tests actually measure. Most commercial tests identify which bacteria are present, at the family or genus level, which tells you who’s there. It doesn’t reliably tell you what they’re doing. Different types of bacteria can carry out the same chemical processes, and two people with very similar bacterial populations can have very different gut function. The more useful information, which genes those bacteria are actively expressing and which metabolites they’re producing, requires a different, far more resource-intensive kind of testing that most direct-to-consumer panels don’t do. That gap between who’s there and what they’re actually doing is where a lot of “your results show X, so take these supplements” advice tends to live, often without evidence that the recommendation improves symptoms.
None of this means the microbiome doesn’t matter. It clearly does. It means the more useful question usually isn’t “which bad bacteria are causing my IBS,” but “which parts of my digestive system aren’t working the way they should.” That second question is one a thorough clinical assessment can actually help answer, in a way a standalone stool test currently can’t.
Does an IBS diagnosis mean doctors have stopped looking?
No. Appropriate medical investigation is still an important part of digestive care, and new symptoms, significant changes, or warning signs may call for further evaluation. But once that investigation is complete, repeating tests in search of structural disease usually won’t provide answers if the underlying problem is a DGBI. An IBS diagnosis shouldn’t mean “we tested you and couldn’t find anything.” It should give you a framework for understanding what’s driving your symptoms, and where treatment can be directed.
How does understanding DGBI change treatment?
It moves care away from searching for one cause or one universal fix. Depending on the person, treatment might focus on improving bowel movement and flow, addressing constipation or diarrhea, improving evacuation and pelvic floor coordination, soluble fibre, targeted dietary strategies, medication when appropriate, pelvic floor physiotherapy and biofeedback, gut-directed hypnotherapy, GI-focused psychological therapy, regular meal patterns, sleep and activity, or reducing visceral hypersensitivity. Not everyone needs all of these. The relevant question is which mechanisms appear to be contributing to your IBS specifically.
What Rome V means for you?
Rome V continues an important shift in digestive medicine. IBS isn’t simply a diagnosis given when every test comes back normal. It’s a disorder involving the systems that regulate gastrointestinal movement, sensation and communication, and that shift opens up better questions than “what’s wrong with my gut.” Does your digestive system need help moving? Emptying? Tolerating normal stretch? Coordinating the pelvic floor? Processing digestive signals? Regulating communication between gut and brain? Those are questions that actually lead somewhere.
If you’ve spent years trying to track down the one food, bacteria or hidden problem behind your IBS, understanding it as a DGBI offers a different way forward. Your symptoms are real, normal test results can be reassuring rather than dismissive, and there are evidence-based ways to improve how your digestive system operates.
That starting point is different for everyone, which is why it usually takes a proper assessment to find. At The Tummy Clinic, every new patient starts there: a comprehensive naturopathic assessment that looks at which of these mechanisms are actually driving your symptoms, before building a plan around nutrition, motility, pelvic floor care, gut-brain therapies or medical care as needed. If you’re ready to find out what’s behind yours, [book an assessment] to get started.
Clinical Perspective by
Dr. Tracey Beaulne, ND
Co-Founder of The Tummy Clinic, a virtual clinic focused on evidence-based care for Disorders of Gut–Brain Interaction (DGBIs), including IBS. Dr. Beaulne works with patients across Ontario to help them understand and manage complex digestive symptoms using a whole-system approach grounded in modern neurogastroenterology.
