Quick answer
"Leaky gut" is the popular name for increased intestinal permeability. In medicine, changes in permeability are clearly seen in conditions like celiac disease and inflammatory bowel disease. In other situations, it is less clear whether permeability is the main cause of symptoms or a side effect of inflammation. If you suspect it, focus on the drivers: inflammation, infections, medication factors, alcohol excess, and nutrient gaps.
- Best starting point: diagnose and treat underlying conditions, improve diet quality, and reduce irritants.
- Testing exists but is imperfect: many markers are not specific and can be hard to interpret.
- Big picture: barrier function usually improves when inflammation and triggers are addressed.
What intestinal permeability means
Your intestinal lining is a selective barrier. Nutrients and water pass through. Many microbes, toxins, and large food proteins should not. "Increased permeability" is when that filtering becomes less tight, often alongside inflammation or injury.
Permeability is not automatically "bad". The gut has to be permeable enough to absorb nutrients. The problem is when permeability increases in a way that contributes to immune activation, symptoms, or nutrient problems.
What we know (and what we do not)
Where the science is strongest
Barrier changes are well described in celiac disease and inflammatory bowel disease. Treating the underlying disease tends to improve barrier integrity.
Where things get fuzzy
For IBS-like symptoms or vague systemic complaints, "leaky gut" is sometimes used as a universal explanation. Research is mixed. Permeability may be increased in some subsets, but it is not always clear whether it is the root cause, a consequence, or one piece of a bigger picture (motility, visceral hypersensitivity, diet, stress, infections).
Symptoms people often blame on "leaky gut"
There is no symptom list that proves permeability is the issue. Still, people commonly report:
- Bloating, discomfort after meals, irregular stools
- Food reactions or new sensitivities (not the same as true allergies)
- Fatigue
- Skin flares that seem linked to digestion
- Brain fog (many possible causes)
Common drivers that can increase permeability
- Inflammatory gut conditions: celiac disease, Crohn's, ulcerative colitis.
- Infections: gastroenteritis can cause temporary barrier disruption; some chronic infections can contribute too.
- Medications: NSAIDs can irritate the GI lining; other meds can affect microbiome or motility.
- Alcohol excess: associated with barrier disruption and inflammation.
- Diet patterns: highly processed diets may worsen inflammation in susceptible people; very low fiber can reduce beneficial microbial metabolites.
- Stress and poor sleep: can amplify gut symptoms and may affect neuro-immune regulation.
Testing: options and limits
Lactulose-mannitol (dual sugar) testing
This urine-based approach is commonly used in research and sometimes clinically. It can be informative, but interpretation depends on the protocol.
Zonulin
Zonulin is often marketed as a "leaky gut" marker. Some commercial tests have limitations, and elevated levels are not always specific. If you use it, interpret it cautiously and in context.
What to do in practice
- Rule out major disease: persistent symptoms deserve a real workup.
- Reduce irritants: limit alcohol and ultra-processed foods; be thoughtful with frequent NSAID use.
- Support basics: adequate protein, fiber as tolerated, sleep, and stress recovery.
- Avoid supplement whack-a-mole: one product rarely fixes a multi-factor problem.
Medical disclaimer: Educational content only. If you have red flags like blood in stool, persistent fever, severe pain, unexplained weight loss, anemia, or ongoing diarrhea, seek medical evaluation.