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Medically reviewed by Rashmi Gulati, MD — Last updated: October 29, 2026
A few supplements have real human data behind them for a “leaky” gut lining: L-glutamine, zinc, and vitamin D when you’re low. Many popular ones rest on lab or animal studies only. This guide grades each supplement by its evidence, gives the doses actually used in studies, and explains why finding the cause of the leak matters more than any capsule.
IBS patients who improved on glutamine vs. placebo in an 8-week trial
Rise in gut permeability from an NSAID, blocked by zinc carnosine in a small study
Supplements the FDA approves for safety or effect before sale
L-glutamine has the strongest human evidence: in a randomized trial of people with post-infectious IBS and a leaky gut, 5 g three times a day for 8 weeks improved both symptoms and gut permeability. Zinc (including zinc carnosine) and vitamin D, when your level is low, have smaller supporting trials. Probiotics show mixed results that depend on the strain. Collagen, bone broth, curcumin, DGL and slippery elm lack human permeability trials.
L-glutamine, from a randomized trial in post-infectious IBS
Zinc, zinc carnosine, vitamin D if low, colostrum, some probiotics
Collagen, bone broth, curcumin, DGL, slippery elm, berberine
Blood in stool, weight loss, anemia, night-time diarrhea
Increased intestinal permeability is clearly seen in celiac disease and inflammatory bowel disease, and in some people with IBS. Links to other symptoms are still being studied, so these complaints need a proper workup rather than a guess.
See the full guide to symptoms of leaky gut, or learn what a leaky gut is.
Supplements work best when you know what’s behind the leak. These guides cover the conditions most often linked to it.
Each supplement is labelled by the strength of human evidence for gut permeability, not by popularity. Numbers in brackets match the references at the bottom of this page.
Fuel for the cells lining the gut. In 106 analyzed adults with post-infectious IBS and raised permeability, 5 g three times daily for 8 weeks cut symptoms in 79.6% vs. 5.8% on placebo and improved a permeability test.
In 10 healthy volunteers, an NSAID tripled gut permeability over 5 days; taking 37.5 mg zinc carnosine twice daily alongside it prevented the rise. Most useful if you need NSAIDs.
Zinc deficiency is common in Crohn’s disease, and a small study found zinc supplements improved permeability in patients in remission. Adults shouldn’t exceed 40 mg a day long term without supervision.
In a 3-month randomized trial in 27 people with Crohn’s in remission, 2,000 IU a day kept permeability stable while it worsened on placebo. Test your level before taking high doses.
Effects depend on the strain. A systematic review found 11 of 12 animal studies helped permeability, but only about half of 14 human trials did. Pick a strain studied for your problem.
Reduced the rise in gut permeability caused by heavy exercise in small studies of athletes. Data outside that setting is thin, and it’s a dairy product.
Fiber feeds bacteria that make butyrate, the main fuel for colon cells. Start low: inulin and FOS can worsen bloating in IBS, where a short low-FODMAP diet may help first.
Strong lab and animal rationale, but few human trials measure permeability directly. Getting more fiber is the proven way to raise butyrate.
Protects gut barrier cells in lab studies. Human permeability data is lacking, and it can interact with blood thinners.
Soothing tradition, no human permeability trials. Choose DGL only: regular licorice contains glycyrrhizin, which can raise blood pressure and lower potassium.
Mucilage herbs that coat the throat and gut. No trials show they repair the gut lining. They can slow absorption of medicines taken at the same time.
Popular, but no controlled human study shows they reduce gut permeability. Fine as food; not a treatment.
Cleveland Clinic notes that the only known cure for increased permeability is treating the condition behind it [1]. These are the causes we look for first.
Regular ibuprofen, naproxen or aspirin can damage the gut lining; in one study 5 days of an NSAID tripled permeability. Ask your doctor about alternatives before adding supplements.
Chronic heavy drinking is a recognized cause of increased permeability. Cutting back often does more than any capsule.
Gluten damages the small intestine in celiac disease, and permeability improves on a strict gluten-free diet. Get tested before going gluten-free, or the test can turn falsely negative.
Crohn’s disease and ulcerative colitis raise permeability. They need medical treatment; supplements are add-ons, never substitutes.
A gut infection can leave lasting IBS and a leaky lining, the group that responded to glutamine. SIBO and yeast overgrowth are also checked when symptoms fit.
Food allergies trigger immune reactions in the gut, and diet and stress may play a part, though the science there is less certain.
These are the doses researchers tested, not a prescription. Your doctor may adjust them for your labs, medicines and other conditions.
| SUPPLEMENT | DOSE STUDIED | STUDIED IN | SAFETY NOTES |
|---|---|---|---|
| L-glutamine | 5 g, 3× daily, 8 weeks | Post-infectious IBS with diarrhea | Ask first if you have kidney or liver disease |
| Zinc carnosine | 37.5 mg, 2× daily | Healthy adults taking an NSAID | Counts toward your total daily zinc |
| Zinc | Dose set by blood level | Crohn’s disease in remission | Above 40 mg/day long term can cause copper deficiency |
| Vitamin D | 2,000 IU daily, 3 months | Crohn’s disease in remission | Test first; upper limit for adults is 4,000 IU/day |
| Probiotics | Strain-specific | Mixed human results | Caution if immunocompromised or seriously ill |
| Bovine colostrum | Varies by study | Athletes during heavy exercise | Dairy product; avoid with milk allergy |
| DGL | Not established | No permeability trials | Use DGL only; whole licorice raises blood pressure |
Four steps, so you only take what your results support.
Symptoms, diet, alcohol, NSAIDs and other medicines, past infections, and every supplement you already take, reviewed at your first visit.
Celiac blood tests, stool markers of inflammation, and stool testing when infection or overgrowth fits. Zonulin blood kits are unreliable: one widely used kit didn’t detect zonulin at all.
Diet changes first, then supplements matched to your results, such as glutamine for post-infectious IBS or vitamin D if you’re low, at studied doses.
We check symptoms and repeat labs where useful, then stop what isn’t working instead of adding more.
Supplements are one tool. These are the other parts of a plan, and the ones we don’t recommend.
A fiber-rich, mostly whole-food diet, with a short guided low-FODMAP trial when IBS symptoms are strong.
Celiac disease, IBD, infections and overgrowth each need their own treatment. Fixing them is what actually closes the gap.
Integrative care for bloating, IBS and SIBO, with referral to a gastroenterologist when scopes or IBD care are needed.
When gut symptoms come with autoimmune disease, we coordinate gut care with your wider treatment plan.
True food allergies are tested properly. IgG “food sensitivity” panels aren’t used on their own to cut foods.
Long “gut repair” stacks of 10+ products, unproven zonulin tests, and cutting whole food groups without a reason. More pills isn’t better care.
The FDA doesn’t approve supplements before they’re sold, so quality and dose accuracy are up to the maker [10]. Use this checklist before you spend money.
Adults enrolled in the glutamine trial, the largest permeability RCT here.
Trial length for glutamine at 5 g three times daily.
Daily vitamin D that kept permeability stable in Crohn’s.
Animal vs. human probiotic studies showing a permeability benefit.
Serving New York patients since 1974.
We rule out celiac disease, IBD and infection before building a plan.
Supplements chosen from published trials and your own labs, not a one-size stack.
Medical doctors check interactions with your prescriptions.
We look for what’s damaging the gut lining so results last.
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L-glutamine has the best human evidence. Zinc or zinc carnosine and vitamin D (if your level is low) have smaller supporting trials, and some probiotics help depending on the strain. Collagen, bone broth, curcumin and DGL lack human permeability trials.
If you have IBS that started after a gut infection, L-glutamine at 5 g three times daily is the best-studied option. For everyone else, the best supplement is the one that corrects what your tests show, such as low vitamin D or zinc.
The trial that showed benefit used 5 g three times a day for 8 weeks. Check with your doctor first if you have kidney or liver disease.
Sometimes. In a systematic review, most animal studies showed a benefit but only about half of human trials did. The strain matters, so choose one studied for your condition.
There are no controlled human trials showing collagen or bone broth reduce gut permeability. They’re fine as food but shouldn’t replace proven steps.
Increased intestinal permeability is real and well documented in celiac disease and IBD. “Leaky gut syndrome” as a stand-alone diagnosis isn’t officially recognized, and it’s unclear whether permeability causes other conditions or results from them
Research studies use sugar-absorption tests such as lactulose-mannitol. Popular zonulin blood tests are unreliable. In practice, doctors look for causes such as celiac disease, IBD and infections.
Remove what’s damaging the lining (NSAIDs, alcohol, gluten if you have celiac disease, untreated infection) and treat the underlying condition. Supplement trials typically run 8–12 weeks.
No medicine is approved to treat leaky gut itself. Medicines treat the cause, such as IBD drugs or antibiotics for an infection, and that is what improves permeability.
Often yes, but check first. Licorice can interact with steroids and affect blood pressure, curcumin can affect blood thinners, and mucilage herbs can slow medicine absorption.
Many haven’t been studied in pregnancy, and large amounts of licorice are unsafe. Talk to your obstetrician before starting any supplement.
Blends often use low doses of many ingredients, below the amounts studied. A single ingredient at a studied dose is easier to judge and safer.
Yes. We offer leaky gut treatment at our Fifth Avenue office and by telemedicine, starting with testing for the cause. Call (212) 794-8800 to book.
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