Leaky Gut - symptoms, causes and how to heal it

Saskia Knight, Gut Health Nutritionist
Written by Saskia Knight, DipNT Published 11 February 2025
Sonia Khan, Pharmacist
Medically reviewed by Sonia Khan, Pharmacist Last reviewed 17 August 2026

What is leaky gut?

Leaky gut, known in research as increased intestinal permeability, describes a gut lining that has become more porous than it should be. When the lining is weakened, partly digested food, toxins and bacteria can pass through the intestinal wall into the bloodstream, where they can trigger inflammation and immune reactions.

Increased intestinal permeability is real and measurable. Leaky gut syndrome as a condition in its own right is different: it is not a recognised medical diagnosis, and the NHS does not list it as a condition. A 2019 review in the journal Gut found that a leakier lining is seen in several diseases, but that none has been shown to be cured by restoring the barrier.

What is the gut barrier?

The gut barrier absorbs water and essential nutrients from food while keeping harmful substances out of your circulation.

It is a system with several layers:

  • Epithelial cells: these form a tight barrier lining the intestines.
  • Tight junction proteins: these hold the epithelial cells together, controlling what passes into the bloodstream.
  • Mucus layer: this protects the gut lining and supports beneficial gut bacteria. A 2024 review found low-fibre diets and emulsifiers can weaken this layer.
  • Gut microbiome: the trillions of microbes in the intestines that help regulate immunity and digestion.

Where permeability increases, it usually reflects consistent, prolonged pressure on the lining from common everyday factors.

What causes leaky gut?

There is no definitive understanding of what causes increased intestinal permeability, but several factors are believed to contribute:

Poor diet

A diet high in processed foods, refined sugars and unhealthy fats can weaken the gut lining. Specific culprits include:

The western diet, high in alcohol, added sugar, food additives and processed foods and low in fibre, is often a contributing factor.

Chronic stress

Stress measurably changes the gut. In one experiment, the stress of public speaking increased intestinal permeability in healthy volunteers within two hours, driven by the body’s stress hormones. Ongoing stress and cortisol can also alter the composition of the gut microbiome.

Gut dysbiosis: an imbalance of bacteria

A healthy gut microbiome consists of trillions of beneficial and harmful bacteria; the beneficial types keep harmful ones in check and support the gut lining. When harmful bacteria overgrow, causing gut dysbiosis, it can lead to inflammation and increased permeability.

Infections

  • Bacterial infections (e.g. H. pylori)
  • Fungal overgrowth (e.g. Candida)
  • Environmental toxins, pesticides, and heavy metals

The evidence for each of these varies, and much of it is early.

Medications

Certain medications have been linked to gut barrier dysfunction, directly or by altering the balance of bacteria within the gut microbiome:

None of this is a reason to stop a prescribed medicine. If you are worried, speak to your GP or pharmacist before changing anything.

Chronic inflammation and autoimmune diseases

Increased permeability is seen in coeliac disease, Crohn’s disease and irritable bowel syndrome (IBS), and has been reported in autoimmune diseases such as rheumatoid arthritis, type 1 diabetes and multiple sclerosis. Which comes first is not settled: a leakier gut may contribute to these conditions, result from them, or both.

What are the symptoms of leaky gut?

There is no agreed set of symptoms for leaky gut, because it is not a defined condition. Those most often linked to increased permeability are general gut and inflammation symptoms, and each has other, more common explanations.

Symptoms discussed in connection with leaky gut include:

Digestive symptoms

Other symptoms

  • Fatigue and brain fog
  • Joint pain
  • Skin and gut issues (eczema, acne, psoriasis)
  • Frequent headaches

Immune and inflammatory symptoms

  • Autoimmune flare-ups
  • Allergies and asthma
  • Chronic inflammation

Having several of these symptoms does not mean your gut is leaky. If they persist, look for the cause with your GP rather than assuming a label.

What conditions are linked to leaky gut?

Research links increased intestinal permeability with a range of conditions, including:

  • Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD)
  • Food sensitivities and allergies
  • Autoimmune diseases such as rheumatoid arthritis and multiple sclerosis
  • Skin conditions like eczema, psoriasis, and acne
  • Mood disorders such as anxiety, chronic fatigue, depression, and brain fog
  • Joint pain
  • Metabolic disorders such as obesity and type 2 diabetes

A 2025 review in The Lancet Gastroenterology and Hepatology describes how a disturbed gut barrier is being studied across these conditions, with treatments targeting it now in development. These remain associations: it has not been shown that a leaky gut causes them, or that repairing the barrier prevents or treats them.

Why addressing your gut health is still worthwhile

Even without a formal diagnosis, a struggling gut is worth taking seriously. Your gut affects digestion, immunity and energy, and research suggests a persistently disturbed gut microbiome can contribute to chronic diseases over time. Supporting it through diet and lifestyle is low risk and worth doing, but it is not a treatment for any disease, and persistent symptoms still need a proper explanation from a clinician.

How to test for leaky gut

There is no definitive way to diagnose leaky gut, and no test confirms it as the cause of your symptoms. Some tests can measure aspects of permeability or overall gut health, each with caveats:

Urine test

You drink a solution containing two different sizes of sugar molecule; if the larger ones reach your urine, it can indicate increased permeability. It is the closest thing to a direct measurement, but mainly a research tool, not routine NHS care.

Zonulin test

Zonulin is a protein involved in opening the tight junctions between gut cells, and zonulin blood tests are sold as leaky gut tests. Treat the results with caution: when researchers examined the two most widely used commercial zonulin kits, the kits were detecting other proteins, not zonulin itself.

Microbiome test

A gut microbiome test does not measure permeability, and no home test diagnoses leaky gut or any other condition. What a microbiome test can show is the balance and variety of your gut bacteria, pointing to gut dysbiosis or bacterial overgrowth, two factors linked with a weakened barrier.

Regardless of the method used, testing for leaky gut is likely to be multi-faceted, combining testing, symptom assessment and dietary and lifestyle changes, ideally alongside your GP.

How to heal leaky gut naturally

No diet or supplement has been proven to heal leaky gut, so be wary of anything sold on that promise. What you can do is reduce the pressures known to weaken the gut barrier and give your gut bacteria what they need.

Adopt a gut friendly diet

Focus on gut friendly foods that support your gut bacteria and, through them, the gut lining.

Foods to include

  • Fermented foods with live cultures (kefir, sauerkraut, kimchi, yoghurt, miso) may help support beneficial bacteria like Bifidobacterium. In a Stanford trial of 36 adults, 17 weeks of a fermented-food-rich diet increased the variety of gut bacteria and lowered markers of inflammation.
  • Omega-3-rich foods (e.g. oily fish, flaxseeds, chia seeds) may help calm inflammation.
  • Leafy greens and colourful vegetables: high in antioxidants and fibre to nourish gut bacteria.
  • Prebiotic foods (e.g. garlic, onions, bananas) feed good bacteria.

Foods to avoid

  • Processed foods and refined sugars
  • Gluten (if sensitive)
  • Dairy (if lactose intolerant)
  • Alcohol and caffeine in excess

Do not cut out whole food groups long term on suspicion alone; if you think a food is a problem, ask your GP or a registered dietitian before eliminating it.

Lifestyle changes

Chronic stress weakens the gut barrier, so managing it matters. Practices that help include:

  • Mindfulness and meditation
  • Gentle exercise (e.g. yoga, walking)
  • Adequate sleep
  • Spending time outdoors
  • Socialising

Medicines and your gut

Antibiotics and NSAIDs can disturb the gut, but that is never a reason to stop a prescribed medicine. Take antibiotics exactly as directed and finish the course, and if you often use anti-inflammatory painkillers you buy yourself, ask your pharmacist about protecting your stomach and gut. Once a course of antibiotics is finished, our guide to how to help your gut recover after antibiotics covers what helps.

Treatments for leaky gut

Because leaky gut is not a single recognised diagnosis, there is no licensed treatment for it. An appropriate protocol should begin by identifying and treating any underlying condition causing symptoms. Beyond that, the most supportive measures include a balanced diet with adequate soluble fibre, limiting alcohol, avoiding unnecessary NSAID use, and fermented foods or supplements with live cultures. A 2025 analysis pooling dozens of trials found such supplements improved some blood markers linked to permeability, though trial quality varied widely, so this is promising rather than proven.

L-glutamine and zinc carnosine have early human evidence. In one trial, 106 people whose IBS began after a gut infection took glutamine or a placebo for 8 weeks; the glutamine group improved markedly and their raised permeability returned to normal, though larger trials are needed. Zinc carnosine reduced the rise in permeability caused by anti-inflammatory painkillers in a study of 10 volunteers. Neither is proven, and if you are considering supplements alongside other medicines, check with your pharmacist first. BPC-157 peptides are being investigated for their possible protective effects on the intestinal barrier, particularly following NSAID-related damage, but the evidence is predominantly preclinical and based on animal studies and it is not an approved treatment for leaky gut and likely won’t be for some time. We cover the full evidence picture in our guide to BPC-157 and gut health. Read the published BPC-157 research here.

When should you see a GP?

Most gut symptoms settle on their own, but some need a doctor rather than a diet change or a test kit. Book a GP appointment promptly if you notice any of the following:

  • Blood in your stool, or black, tarry stools
  • Unexplained weight loss
  • A change in your usual bowel habit lasting more than three weeks
  • Difficulty or pain when swallowing
  • Persistent vomiting
  • A new lump in your tummy, or ongoing tummy pain
  • Iron-deficiency anaemia found on a blood test
  • New digestive symptoms starting over the age of 50, or a family history of bowel or ovarian cancer

These symptoms have many possible causes, most of them treatable, but they need proper investigation, and a home gut test is never a substitute for seeing a GP about them. This guide is for information only and does not replace medical advice. If ongoing symptoms affect your daily life, even without the warning signs above, your GP is still the right first stop.

Saskia’s thoughts

Gut permeability is one of the most active areas of gut health research. The barrier is real and it matters; the syndrome built around it is not yet a recognised condition. What the evidence supports now is unglamorous: a varied, fibre-rich diet, less alcohol and ultra processed food, managed stress and decent sleep, with persistent symptoms properly investigated rather than labelled.

If you suspect your gut is struggling, start with those foundations. A microbiome test can show what is happening with your gut bacteria, and working with a healthcare professional can help you act on anything it finds.

Sources

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Medically reviewed by Nutritionist Saskia Knight BA DipNT