Leaky gut. Real condition or myth?

In 2026, a team tried to make healthy volunteers’ guts “leaky” on purpose with a strong painkiller, a classic method in research. It did not work. Their gut barriers held up far better than expected.

That small study says a lot. The gut barrier is real, and it can weaken. Yet the version of leaky gut you see on social media, with home tests, strict diets and costly supplements, goes well beyond the science. In this guide I explain what is real, what is myth and what actually helps your gut lining.

What is leaky gut?

Leaky gut is a popular name for increased intestinal permeability, which means the gut lining lets more through than it should. Doctors use the term “intestinal barrier dysfunction” instead.

Your gut barrier has several layers. A 2019 review in the journal Gut, led by Mayo Clinic expert Michael Camilleri, describes them simply. There is a layer of mucus, a single layer of cells joined by tight seals, and the immune defences underneath. Together they let nutrients in and keep most bacteria and toxins out.

Is leaky gut a real condition or a myth?

Increased gut permeability is real, but “leaky gut syndrome” as a cause of almost every illness is not proven. The 2019 Gut review is clear on both points.

It says inflammatory and ulcer-causing gut diseases do cause a leaky gut. Yet no such disease can be cured simply by fixing the barrier. It also says it is still unproven that restoring the barrier improves symptoms in gut or whole-body diseases.

The review also warned that online claims about a “healthy” or “leaky” gut need confirmation. That covers food exclusions, special healing foods and supplements to repair the damage. So the honest answer is this. A leaky barrier is a real finding in some people, but it is usually a sign of something else, not a diagnosis on its own.

What causes a leaky gut?

Several everyday stresses can loosen the gut barrier for a while. The 2019 review lists endurance exercise, painkillers called NSAIDs, pregnancy, bile acids and food additives called emulsifiers.

Stress

Mental stress can open the gut barrier in humans. In a 2014 study in Gut, 23 healthy volunteers had their gut permeability tested under different conditions. Giving a public speech made their small intestine more leaky, but only in people whose stress hormone cortisol went up.

The researchers traced the effect to mast cells, immune cells in the gut wall that react to a stress hormone called CRH. I strongly believe this is one reason stress and gut symptoms travel together. My guide to the gut-brain axis explains the link.

Painkillers

NSAIDs such as ibuprofen can damage the gut lining, which is why researchers use them to test the barrier. Yet the 2026 trial I mentioned at the start gave 150 mg a day of indomethacin for 6 days. It did not raise gut permeability in healthy volunteers. The authors said this research model may be less reliable than people thought.

Food additives

Some emulsifiers in processed food may harm the gut lining. In a 2022 feeding trial, 16 healthy adults ate either an additive-free diet or the same diet with an added emulsifier. The additive was 15 g a day of carboxymethylcellulose (CMC).

After 11 days, the CMC group had a little more belly discomfort, less diverse gut bacteria and fewer short-chain fatty acids. In 2 of the 7 people on CMC, bacteria moved into the inner mucus layer that is normally free of bacteria. It was a very small study, but it is a reason to choose mostly whole foods.

Does leaky gut cause IBS?

It does not explain all IBS, but a weaker barrier is found in many people with IBS. A 2021 review of 66 studies found barrier problems in 37% to 62% of people with IBS with diarrhoea. It was less common in IBS with constipation, at 4% to 25%.

The same review found that all 4 studies in children with IBS showed a weaker barrier. My guide to IBS in teens covers that age group. A 2026 European study then tested 418 people with IBS using a sugar drink test. Their small intestine was more permeable than in 200 people with other gut problems.

That finding held for every IBS type and for both sexes. Anxiety or other health problems did not explain it. Yet results varied a lot between the 9 centres. So barrier changes look like one part of IBS for some people, not the whole story.

Can a test tell me if I have leaky gut?

No reliable home or blood test can diagnose leaky gut today. Research centres measure permeability with sugar drink tests, where you drink sugars such as lactulose and mannitol and then collect urine for hours. These tests are mainly used in studies.

Many clinics sell a blood test for a protein called zonulin. Two independent studies found a problem. A 2018 German study of 376 people showed that a widely used zonulin test kit did not detect zonulin at all. A 2019 Australian study found the same with 2 commercial kits, which picked up other blood proteins instead.

The Australian team advised caution in using zonulin as a marker of the gut barrier. So if someone offers you a zonulin test, please save your money.

What helps a leaky gut?

The best evidence supports looking after your whole gut, rather than chasing a quick cure. Here is what the research suggests.

Eat more plants and polyphenols

Colourful plant foods may help the barrier. In the MaPLE trial, 51 adults aged 60 or over ate a polyphenol-rich diet for 8 weeks. It included foods such as cocoa and green tea. Their markers of gut permeability went down, alongside more of the helpful bacteria that make butyrate. One caution is that the trial used zonulin, the test I questioned above, so treat this as early evidence.

Butyrate is a short-chain fatty acid that feeds the cells of your gut lining. You make more of it when your gut bacteria ferment fibre. My game Gut Garden shows how many different plants you can fit into a week.

Is glutamine good for leaky gut?

Glutamine shows promise for one group of people with IBS, but it is not proven for everyone. In a 2019 trial in Gut, 106 adults had IBS with diarrhoea that started after a gut infection, plus a leaky barrier on testing.

Those taking 5 g of glutamine 3 times a day for 8 weeks did far better. About 80% improved, compared with about 6% on placebo, and their permeability returned to normal. The trial was from 1 centre, and the authors called for larger trials. Please ask your doctor before trying it, as the dose is high and the results are not yet confirmed.

Calm your stress

Because stress can loosen the barrier, calming your nervous system is a sensible step. Slow breathing, sleep and regular movement all help. My free 30-Day Calm Gut Challenge builds these habits one day at a time.

Try this

1. Fill half your plate with plants. Vegetables, fruit, oats, beans, lentils, nuts and seeds all feed your gut bacteria.
2. Add colour daily. Berries, green tea and a little dark chocolate are rich in polyphenols.
3. Cook from whole foods most days. Check labels for emulsifiers such as carboxymethylcellulose (E466) and polysorbate 80 (E433).
4. Use painkillers wisely. Take NSAIDs only as directed, and ask your doctor if you need them often.
5. Increase fibre slowly if you have IBS. My fibermaxxing guide explains how to add fibre without bloating.

Do leaky gut diets and supplements work?

Strict leaky gut diets and “gut repair” supplement kits have no good evidence behind them. The 2019 Gut review said these approaches need confirmation before anyone recommends them.

Cutting out many foods can also harm your gut. Fewer plant foods means less fibre for your gut bacteria. If you have IBS, a short, guided IBS diet plan is a better place to start. Probiotics may help some people with IBS, but choose strains with evidence. My guide to probiotics for IBS explains which ones.

If you love busting health myths, try my Daily Myth game for a new one each day.

When should I see a doctor?

See a doctor if you have gut symptoms that do not settle, rather than guessing the cause. A leaky barrier is often a sign of another condition that needs proper care, such as coeliac disease or inflammatory bowel disease.

Get checked quickly if you notice blood in your stool, weight loss without trying, ongoing diarrhoea or night-time symptoms. Losing 3 kg (about 7 lb) or more without trying is always worth a check. My guide to IBS vs IBD explains the warning signs.

Frequently asked questions

Is leaky gut syndrome real?

Increased gut permeability is real and can be measured in research. “Leaky gut syndrome” as a cause of many illnesses is not proven. A 2019 review in Gut said it is still unproven that repairing the barrier improves symptoms, so be careful of anyone selling a cure.

What are the symptoms of leaky gut?

There is no agreed list of symptoms, because it is not an official diagnosis. A weaker barrier is linked with conditions such as IBS with diarrhoea, coeliac disease and inflammatory bowel disease. Symptoms like bloating, pain and diarrhoea need a doctor’s check to find the real cause.

Is the zonulin test accurate for leaky gut?

Not at the moment. Studies in 2018 and 2019 found that widely used commercial zonulin test kits did not detect real zonulin. They picked up other blood proteins instead. Researchers advise caution, so a zonulin result should not be used to diagnose leaky gut.

How can I heal my gut lining naturally?

Eat plenty of varied plant foods, choose whole foods over heavily processed ones, manage stress and use painkillers wisely. In one trial, a polyphenol-rich diet lowered markers of gut permeability in older adults after 8 weeks. Ask your doctor before trying glutamine or other supplements.

What I want you to remember

Leaky gut is part real and part myth. Your gut barrier is real, and stress, some additives and gut diseases can weaken it. But there is no reliable test for leaky gut syndrome, and no proven cure in a bottle.

Focus on what helps your whole gut. Eat lots of different plants, cook mostly from whole foods, calm your stress and get any lasting symptoms checked. For more gut-friendly habits, start with my complete IBS diet guide.