Leaky gut can be measured, but most “heal your gut” protocols haven’t been tested

Key takeaways

• Your gut lining really does become leakier with endurance exercise, NSAID painkillers and bowel diseases that cause inflammation, but a 2019 review found no disease that is cured by repairing the barrier alone.
• In a 2019 trial of adults whose irritable bowel syndrome began after a gut infection, 79.6% improved on glutamine powder versus 5.8% on a placebo; the authors called for larger trials.
• A 2025 review by a Mayo Clinic team called the evidence that bone broth’s nutrients help the gut barrier preliminary, and said broth still needs clinical trials.
• If you suspect gluten is a problem, get a celiac blood test before you cut it, because the test is accurate only while you’re still eating gluten.
• British guidelines strongly back soluble fiber for IBS and advise against food-elimination diets based on IgG “sensitivity” blood tests.

In 2019, Mayo Clinic researcher Michael Camilleri published a review in the journal Gut on a question that fills wellness feeds: is “leaky gut” real¹?

His answer was yes, with limits. The lining of the gut does become leakier during endurance exercise, with NSAID painkillers, in pregnancy and with exposure to bile acids and some food additives called emulsifiers¹. Diseases that inflame or ulcerate the bowel make it leaky, too¹.

But fixing the leak, Camilleri wrote, has not been shown to cure any of those diseases. Nobody has yet proven that a tighter barrier eases symptoms, whether in the gut or elsewhere in the body¹.

He also had a warning about popular advice. Before anyone recommends cutting foods, switching to fermented foods or taking supplements to repair the gut, he wrote, those ideas need to be confirmed¹.

That’s the honest state of “heal your gut.” There’s a real biological idea underneath it and a large market of protocols built on top. The trials that would connect the two are mostly missing.

Meanwhile, a few plain steps with solid evidence are easy to skip. This guide sorts them out.

Your gut lining is a gate, not a wall

Your intestinal barrier has three layers of protection: a coat of mucus, a lining of cells and immune defenses¹. Its job is to let nutrients through while holding back most of what shouldn’t get in.

Permeability describes how easily substances slip through that lining. Researchers measure it by having people swallow harmless test molecules, such as the sugars lactulose and mannitol, and tracking how much passes through¹². They also study small tissue samples called biopsies¹.

Notice what’s on the list of things that raise permeability: exercise, pregnancy, common painkillers, bile acids and food emulsifiers¹. A leakier gut isn’t automatically a disease. Some looseness is part of ordinary life.

Where the leaky-gut idea holds up, and where it’s stretched

The idea holds up in diseases that inflame or ulcerate the intestine, which come with a leaky barrier¹. Camilleri calls the barrier a possible future target for treatment¹. That is serious science, not fringe talk.

The stretch comes next. In wellness marketing, “leaky gut syndrome” is sometimes presented as a hidden root of fatigue, skin trouble, brain fog and more. You won’t find it on the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) list of about 40 digestive disease topics, which runs from abdominal adhesions to Zollinger-Ellison syndrome³.

Think of the full claim as a chain with four links:

1. Your gut is leakier than normal.
2. The leak causes your symptom.
3. This protocol tightens the leak.
4. Tightening the leak makes the symptom go away.

Research supports the first link in some diseases¹. The third link has some support: diet changes can reverse leakiness in the stress states above, and glutamine did in one trial¹². The weakest links are the second and fourth, especially for symptoms outside the gut¹.

A protocol needs all four links to hold.

Natural-health thinking got some big things right here. Food shapes the gut. Gut microbes matter. Stress and digestion talk to each other.

The 2025–2030 Dietary Guidelines for Americans say high-fiber foods support a diverse microbiome, and they name sauerkraut, kimchi, kefir and miso among fermented foods that support microbial diversity⁴.

What the popular protocols have been tested for

L-glutamine. Glutamine is an amino acid, a building block of protein, and it’s a fixture in gut-healing kits. It also has the most interesting trial.

In a trial published in Gut in 2019, researchers randomly assigned 115 adults to glutamine powder or a placebo of whey protein²⁵. Everyone had diarrhea-type irritable bowel syndrome (IBS) that started after a gut infection, plus a measurably leaky gut². They took 5 grams three times a day for eight weeks².

The results were dramatic. Symptom scores dropped by at least 50 points on a standard IBS severity scale in 79.6% of the glutamine group and 5.8% of the placebo group². Gut permeability returned to normal in the glutamine group but not in the placebo group².

Now the limits. The analysis counted only people who finished, not everyone who was randomized, and the trial was small⁵. It tested one narrow group with a measured leak, not everyone with gut symptoms². The authors themselves called for large trials to confirm it².

That makes glutamine promising but early.

Bone broth. Broth fans point to its amino acids, such as glutamine and glycine. A Mayo Clinic team that included Camilleri pulled together the animal and human research on those nutrients in a 2025 review for the journal Digestive Diseases and Sciences⁶. According to a summary in the European Medical Journal, the authors saw early hints that they help the gut barrier. They also stressed that the evidence is preliminary and that broth still has to prove itself in clinical trials⁶.

One human trial was registered in Australia in 2020. It planned to give 30 people a commercial broth powder for eight weeks after a four-week lead-in, with no separate comparison group. The broth company funded it. The registry entry, last updated when it was filed, lists it as not yet recruiting⁷.

Bone broth is a fine food. As a gut treatment, it still awaits clinical trials⁶.

Elimination diets. The best-studied version is the low-FODMAP diet, which cuts certain fermentable carbohydrates for a short time. The American College of Gastroenterology (ACG) recommends a limited trial for IBS⁸. British guidelines call it a second-line option that should be supervised by a trained dietitian, with a four- to six-week cutting phase followed by adding foods back as tolerated⁹.

Elimination diets built on IgG antibody blood tests, often sold as food-sensitivity tests, are another story. The British Society of Gastroenterology strongly recommends against them for IBS⁹. It also doesn’t recommend a gluten-free diet for IBS, noting that any benefit may come from cutting fructans, a FODMAP carbohydrate also found in wheat⁹.

Probiotics. Here expert groups disagree. The American Gastroenterological Association’s 2020 guideline said probiotics for IBS should be used only in clinical trials, citing knowledge gaps. The panel also noted that studies report harms inconsistently¹⁰.

The 2021 British guideline says people may try one for up to 12 weeks and stop if nothing improves, though no specific strain can be recommended⁹. That is a weak recommendation built on very low-quality evidence⁹.

Get tested for celiac disease before you cut gluten

About 2 million Americans have celiac disease, many without knowing it, and about 1% of people worldwide have it¹¹. In celiac disease, gluten triggers an immune reaction that damages the small intestine¹¹.

Over time, it can lead to weak bones, anemia, malnutrition, and nerve and reproductive problems. Rare complications include a cancer of the small intestine and lymphoma¹¹. Family members of people with celiac disease are at higher risk¹¹.

This is the trap. The preferred first test is a blood test called tTG-IgA, and NIDDK’s guidance for clinicians says a patient must be eating gluten for the results to be accurate¹². Start a gluten-free “gut reset” first, and you can blur the very test that would give you a lifelong answer.

Even done right, about 2% to 3% of people with celiac disease test negative on blood work¹². Both major guidelines call for celiac blood tests in people with IBS-type symptoms. The ACG suggests it for IBS with diarrhea, and the British guideline for anyone first seeing a doctor with IBS symptoms⁸⁹.

If you’ve already gone gluten-free, tell your clinician. Don’t restart gluten on your own to prepare for a test without guidance.

Fiber is the gut habit most Americans skip

The Dietary Guidelines Advisory Committee, the expert panel that reviewed the science for the 2025–2030 guidelines, concluded that Americans underconsume fiber, along with calcium, potassium and vitamin D. The government’s Scientific Foundation report lists that conclusion as only partly adopted in the final guidelines¹³.

The same federal report, released alongside the new guidelines, found that higher fiber intake was linked to a 17% lower risk of death from any cause, rated as moderate-certainty evidence¹³. It also tied fiber to lower risks of colorectal cancer, type 2 diabetes and heart disease, and cited 25 to 29 grams a day as an optimal intake¹³.

Refined grains carry 60% to 80% less fiber than whole grains¹³. A handy label check from the same report: most true whole-grain foods have at least 1 gram of fiber for every 8 grams of carbohydrate¹³.

The guidelines themselves say to prioritize fiber-rich whole grains, at two to four servings a day, and warn that highly processed foods can disrupt the gut microbiome⁴.

For IBS, the type of fiber matters. British guidelines strongly recommend soluble fiber such as ispaghula (psyllium), starting at 3 to 4 grams a day and increasing slowly to limit bloating⁹. They advise avoiding insoluble wheat bran, which can make symptoms worse⁹.

The IBS treatments with real evidence

About 12% of people in the U.S. have IBS¹⁴. Women are up to twice as likely as men to develop it, and people under 50 are more likely than older adults¹⁴.

The ACG’s 2021 guideline favors making a positive diagnosis from symptoms and a few targeted tests, rather than ruling out every other condition first⁸. It recommends a short low-FODMAP trial and suggests gut-directed psychotherapy for overall symptoms⁸.

That last item may surprise people. The British guideline says IBS-focused cognitive behavioral therapy and gut-directed hypnotherapy may ease overall symptoms⁹. It strongly recommends considering them, though it rates the evidence as low quality⁹. These mind-body treatments fit a natural-health outlook well.

Peppermint oil has guideline support as well. The British guideline says it may help overall symptoms and belly pain, with heartburn-type reflux as a common side effect⁹.

A gut-claims decoder

The claim	What’s known	What to do
“You have leaky gut syndrome.”	Leakiness is real in some diseases; fixing it hasn’t been shown to cure them1	Ask which test was used and which diagnosis it points to
“Glutamine heals the gut lining.”	One trial helped post-infection IBS with a measured leak2	If your IBS began after an infection, ask a clinician about it
“Bone broth seals your gut.”	Evidence is preliminary; trials are needed6	Enjoy it as food, not as treatment
“A blood test shows your food sensitivities.”	IgG-based elimination diets aren’t recommended9	Try a dietitian-guided low-FODMAP trial with food reintroduction
“Go gluten-free to calm your gut.”	Celiac tests need gluten in your diet to be accurate12	Get tested first
“Everyone needs a probiotic.”	Expert groups disagree for IBS910	If you try one, stop after 12 weeks without benefit

How strong is the evidence?

Approach	Evidence level	Why
Soluble fiber (psyllium) for IBS	Strong evidence	Strong recommendation, moderate-quality evidence in the British guideline9
Celiac blood test while still eating gluten	Strong evidence	Accuracy depends on current gluten intake12
Gut-directed hypnotherapy or IBS-focused talk therapy	Promising but early	Recommended despite low-quality evidence9
Short, dietitian-led low-FODMAP trial	Promising but early	Recommended by the ACG; British guideline rates evidence very low89
Peppermint oil for IBS	Promising but early	May help; evidence rated very low9
Glutamine for IBS after a gut infection	Promising but early	One striking trial; needs confirmation25
Probiotics for IBS	Not enough evidence	Guidelines disagree910
Bone broth for gut repair	Not enough evidence	Review calls evidence preliminary; trials still needed67
“Leaky gut syndrome” as the cause of whole-body symptoms	Not enough evidence	Repairing the barrier hasn’t been shown to cure disease1
IgG food-sensitivity tests to choose foods to cut	Evidence says no, or unsafe	Strongly recommended against9

When to get help

NIDDK lists signs that point beyond IBS and call for more testing: anemia, bleeding from the rectum, bloody or black, tarry stools, and weight loss¹⁵. A family history of celiac disease, colon cancer or inflammatory bowel disease also calls for a closer look¹⁵.

See a clinician before starting a long protocol if your symptoms are new or getting worse. If your list of safe foods keeps shrinking, ask for a registered dietitian. If a supplement seems to have harmed you, report it to the FDA through MedWatch or the Safety Reporting Portal.

Questions readers ask

The bottom line

Your gut lining is real, dynamic and worth caring for. Researchers take leaky gut seriously as a feature of some diseases. What they haven’t shown is that repairing the barrier cures disease, or that most gut-healing protocols do what they promise.

The steps with the best evidence are less exciting and more useful: enough fiber, a celiac test before going gluten-free and, for IBS, guideline-backed care such as soluble fiber, a guided low-FODMAP trial and gut-directed therapy. Save the experiments for after those basics, and give each one an end date.

Related reading

• Same stool, different verdicts: what home gut microbiome tests can tell you
• Stool became FDA-approved medicine for one infection, and other uses are still experiments
• Your body already detoxes itself, and a few everyday habits help it work
• Most health products aren’t scams, but many just haven’t been proven
• Simple health answers feel true, so how do you tell which ones are?

Sources

1. Camilleri M. “Leaky Gut: Mechanisms, Measurement and Clinical Implications in Humans.” Gut, 2019. pubmed.ncbi.nlm.nih.gov
2. Zhou Q, Verne ML, Fields JZ, et al. “Randomised Placebo-Controlled Trial of Dietary Glutamine Supplements for Postinfectious Irritable Bowel Syndrome.” Gut, 2019. pubmed.ncbi.nlm.nih.gov
3. National Institute of Diabetes and Digestive and Kidney Diseases. “Digestive Diseases” (topic list). NIH, accessed October 2026. niddk.nih.gov
4. U.S. Department of Agriculture and U.S. Department of Health and Human Services. “Dietary Guidelines for Americans, 2025–2030.” January 2026. cdn.realfood.gov
5. Kavanagh A. “Oral Glutamine May Reduce IBS Symptoms in Adults With Post-Infectious IBS With Diarrhea Predominance.” DynaMed Resident Focus, EBSCO (summary of Zhou et al., Gut, 2019). about.ebsco.com
6. European Medical Journal (EMJ). “Bone Broth Strengthens Gut Barrier and Reduces Inflammation” (summary of Matar A, et al., “Bone Broth Benefits: How Its Nutrients Fortify Gut Barrier in Health and Disease,” Digestive Diseases and Sciences, 2025). emjreviews.com
7. Australian New Zealand Clinical Trials Registry. “Effect of Broth & Co Beef Bone Broth on Lower Gastrointestinal Disturbances: The Bone Broth Gut Study” (ACTRN12620000092998). Registered 2020. anzctr.org.au
8. Lacy BE, Pimentel M, Brenner DM, et al. “ACG Clinical Guideline: Management of Irritable Bowel Syndrome.” American Journal of Gastroenterology, 2021 (PubMed abstract). pubmed.ncbi.nlm.nih.gov
9. Vasant DH, Paine PA, Black CJ, et al. “British Society of Gastroenterology Guidelines on the Management of Irritable Bowel Syndrome.” Gut, 2021. gut.bmj.com
10. MDedge. “AGA Probiotic Guideline Reveals Shortage of High-Quality Data” (report on Su GL, et al., American Gastroenterological Association guideline, Gastroenterology, 2020). July 2020. mdedge.com
11. National Institute of Diabetes and Digestive and Kidney Diseases. “Definition & Facts for Celiac Disease.” NIH, accessed October 2026. niddk.nih.gov
12. National Institute of Diabetes and Digestive and Kidney Diseases. “Celiac Disease” (for health care professionals). NIH, accessed October 2026. niddk.nih.gov
13. U.S. Department of Agriculture and U.S. Department of Health and Human Services. “The Scientific Foundation for the Dietary Guidelines for Americans, 2025–2030.” 2026. cdn.realfood.gov
14. National Institute of Diabetes and Digestive and Kidney Diseases. “Definition & Facts for Irritable Bowel Syndrome.” NIH, accessed October 2026. niddk.nih.gov
15. National Institute of Diabetes and Digestive and Kidney Diseases. “Diagnosis of Irritable Bowel Syndrome.” NIH, accessed October 2026. niddk.nih.gov