Quick answer: “Leaky gut” describes increased intestinal permeability: the tight junctions that seal the one-cell-thick lining of your intestine loosen, so more food proteins, bacterial fragments (like LPS) and other particles can reach the bloodstream and activate the immune system. It is linked with digestive symptoms and body-wide inflammation, and it can be assessed with specific stool and blood markers.
Key takeaways
Leaky gut refers to increased intestinal permeability, where the tight junctions in the gut lining loosen.
When this happens, more food proteins and bacterial fragments can reach the bloodstream and stir up the immune system.
Stress, certain medications, alcohol and gut imbalances can raise permeability, and specific stool and blood markers can help assess it.
What happens in a “leaky” gut?
The lining of your small intestine is only one cell thick. Neighboring cells are held together by tight junctions, which act like gates: they let water and nutrients through while keeping larger particles out. When those junctions loosen, larger particles can pass into the bloodstream. These include undigested food proteins, bacterial fragments such as lipopolysaccharide (LPS), and toxins. The result can be low-grade, body-wide inflammation and immune activation.
One protein researchers study here is zonulin, which helps regulate how open or closed those tight junctions are.
Common signs that leaky gut may be playing a role
Common signs include chronic bloating, gas, or irregular bowels, food sensitivities that seem to keep expanding, and brain fog, anxiety, or mood changes. Joint pain or skin issues (eczema, acne, rosacea), autoimmune flares or fatigue, and difficulty losing weight despite effort can also be part of the picture.
None of these symptoms is specific to leaky gut. They are clues that the gut may be part of the bigger picture.
What can increase intestinal permeability?
- Dysbiosis: an imbalance in gut bacteria, including low diversity (see why microbiome diversity matters)
- Gut infections and overgrowth: parasites, yeast, or bacterial overgrowth (see hidden pathogens in the gut and SIBO)
- Low short-chain fatty acids: such as butyrate, which fuels the cells lining the colon (see the gut–brain link and SCFAs)
- Other contributors: psychological stress, heavy alcohol use, frequent NSAID use, and diets low in fiber and high in ultra-processed foods
How it is assessed: key biomarkers
Fecal zonulin is a marker related to tight-junction regulation, and secretory IgA is your gut’s front-line immune defense. Anti-LPS antibodies suggest whether bacterial toxins are crossing the barrier, and calprotectin and other inflammatory markers help separate gut inflammation from functional symptoms.
The value of testing is that we don’t have to guess. Together, these markers can show how permeable the gut may be and what is likely driving it, such as dysbiosis, pathogens or low SCFAs. In my practice, functional labs are available to patients working 1-on-1 with me.
How the gut barrier is supported
Support is matched to what is driving the problem. Common building blocks include specific fibers, glutamine, zinc, quercetin, polyphenol-rich foods, and strain-specific probiotics when appropriate. Many people also need to address stress, sleep and food triggers. If you already work with me, you can find the products I commonly use in my microbiome gut support plan on Fullscript. Please discuss any supplement with your provider before you start it.
Repairing the gut barrier is often foundational work. It can support energy, mood, skin and immunity downstream.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have digestive symptoms that keep coming back despite diet changes or probiotics, or a growing list of food sensitivities. The same is true if you have gut symptoms together with skin, joint, mood or energy problems, or if you want to understand why, not just manage symptoms.
See a medical provider promptly for blood in the stool, black stools, unintended weight loss, persistent vomiting, severe abdominal pain, or fever. These need prompt evaluation.
Ongoing digestive or whole-body symptoms? Let’s talk about what may be driving them.
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Are there stool or blood markers we could use to see whether gut permeability is part of my picture?
Which labs or assessments would help us understand the health of my gut lining in my case?
Which daily habits are most likely to make a difference for the health of my gut lining for me?
How long would it be reasonable to try these steps for the health of my gut lining before we review them together?
Frequently asked questions
Is leaky gut a real medical diagnosis?
Increased intestinal permeability is real and measurable in research settings, and it is studied in conditions such as celiac disease and inflammatory bowel disease. “Leaky gut syndrome” is not a formal diagnosis, and research on how it affects symptoms in otherwise healthy people is still developing.
What are common signs that gut permeability may be involved?
People often describe bloating, gas, irregular bowels, a growing list of food sensitivities, brain fog, skin flares, joint aches or fatigue. These symptoms have many possible causes, so they are a reason to look deeper, not proof of leaky gut.
How is intestinal permeability tested?
Options include stool markers such as zonulin, secretory IgA and calprotectin, and blood markers such as antibodies to bacterial LPS. No single test is perfect, so results are interpreted together with your history and symptoms.
How long does it take to support the gut lining?
It varies from person to person. Gut-support plans are usually reassessed over several weeks to a few months, with changes based on how symptoms respond.
Sources
- Fasano A. Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer. Physiol Rev 2011. PMID: 21248165. https://pubmed.ncbi.nlm.nih.gov/21248165/
- Vanuytsel T, et al. Psychological stress and corticotropin-releasing hormone increase intestinal permeability in humans by a mast cell-dependent mechanism. Gut 2014. PMID: 24153250. https://pubmed.ncbi.nlm.nih.gov/24153250/
- Bjarnason I, et al. Mechanisms of Damage to the Gastrointestinal Tract From Nonsteroidal Anti-Inflammatory Drugs. Gastroenterology 2018. PMID: 29221664. https://pubmed.ncbi.nlm.nih.gov/29221664/
- Mantis NJ, Rol N, Corthésy B. Secretory IgA’s complex roles in immunity and mucosal homeostasis in the gut. Mucosal Immunol 2011. PMID: 21975936. https://pmc.ncbi.nlm.nih.gov/articles/PMC3774538/
- van Rheenen PF, Van de Vijver E, Fidler V. Faecal calprotectin for screening of patients with suspected inflammatory bowel disease: diagnostic meta-analysis. BMJ 2010. PMID: 20634346. https://pmc.ncbi.nlm.nih.gov/articles/PMC2904879/
- Camilleri M. Leaky gut: mechanisms, measurement and clinical implications in humans. Gut. 2019 (PubMed)
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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