Apr 25, 2026

How to Heal Leaky Gut: A Research-Backed Protocol

By The Luna Lab Research Team · 11 min read

TLDR:

“Leaky gut” is the popular term for increased intestinal permeability — a real, measurable phenomenon that’s well-documented in peer-reviewed research, even if the term itself is overused in wellness marketing.
The intestinal barrier’s tight junctions are regulated by a protein called zonulin, discovered by Dr. Alessio Fasano. Triggers including gluten, bacterial overgrowth, chronic stress, and certain medications can elevate zonulin and loosen the barrier.
Healing the gut lining works on three fronts: (1) remove the triggers that are loosening it, (2) provide the raw materials epithelial cells need to repair, (3) rebalance the microbiome.
Strong evidence supports L-glutamine, certain probiotic strains, mucilaginous herbs (slippery elm, marshmallow, aloe), and quercetin. The Luna Lab Gut Lining Reset is built around exactly these ingredients.
Realistic timeline: 60–90 days of consistent support is generally needed for meaningful repair. There’s no quick fix.

“Leaky gut” is one of those terms that lives in two different worlds simultaneously. In wellness marketing, it’s sometimes invoked to explain almost any chronic symptom — usually with a product to sell at the end. In medical research, the underlying phenomenon (increased intestinal permeability) is taken much more seriously than skeptics in the wellness debate often acknowledge.

This guide covers what the research actually shows: what intestinal permeability is, what causes it, what helps repair it, and how a thoughtful 60–90 day protocol fits in. We’ll also be honest about where the evidence is strong, where it’s still developing, and where the wellness space gets ahead of the science.

What “leaky gut” actually means

Your intestinal lining is a single layer of cells — just one cell thick — that separates the contents of your gut from your bloodstream. This is one of the most extraordinary interfaces in the body: it has to let nutrients through while keeping microbes, partially digested food, and toxins out.

The barrier function relies on tight junctions: protein structures between cells that control what passes between them (the “paracellular” route). When tight junctions loosen, larger molecules — including bacterial fragments and incompletely digested proteins — can cross into the bloodstream. The immune system, encountering these molecules where they shouldn’t be, mounts a response. Sustained over time, that response is thought to contribute to chronic low-grade inflammation, which has been associated with autoimmune conditions, food sensitivities, IBD, IBS, metabolic disease, and certain mood disorders.

This is the real phenomenon behind “leaky gut.” The medical name is increased intestinal permeability or impaired intestinal barrier function. It’s measurable in the lab (most reliably with the lactulose-mannitol test), and it’s a documented feature of multiple disease states.

Zonulin: the discovery that changed the conversation

For a long time, intestinal tight junctions were assumed to be relatively static. That changed in the early 2000s when Dr. Alessio Fasano and colleagues identified zonulin — the first known physiological regulator of tight junctions.

Zonulin is a protein released by intestinal cells in response to specific triggers. When zonulin binds to receptors on the intestinal epithelium, it causes the tight junctions to temporarily disassemble — loosening the barrier. This is normally a controlled, transient process that helps the gut function (for example, allowing immune surveillance). But chronic over-release of zonulin, in response to chronic triggers, can keep the barrier in a persistently loose state.

Two of the most-studied zonulin triggers:

Gliadin, the prolamin protein component of gluten. In susceptible individuals, gliadin is a potent zonulin releaser. This is part of the mechanism behind celiac disease and is one reason gluten removal helps people with non-celiac gluten sensitivity.
Bacterial overgrowth in the small intestine. When enteric bacteria reach the small intestine in abnormal numbers (as in SIBO), they trigger zonulin release. This is part of the link between SIBO, leaky gut, and downstream symptoms.

Read Fasano’s comprehensive review for the full picture: All disease begins in the (leaky) gut: role of zonulin-mediated gut permeability in the pathogenesis of some chronic inflammatory diseases. PMC.

What causes increased intestinal permeability

Beyond gluten and bacterial overgrowth, the well-documented contributors include:

Chronic stress — cortisol and stress hormones directly affect intestinal barrier function
NSAIDs (ibuprofen, aspirin, naproxen) — long-term use damages the gut lining
Frequent antibiotic exposure — disrupts the microbiome that normally supports the barrier
Alcohol — particularly in chronic or heavy use
Ultra-processed diet, high refined sugar — contributes to dysbiosis and inflammatory signaling
Intestinal infections (Giardia, food poisoning, gastroenteritis) — can cause persistent permeability changes long after the acute infection clears
Chronic illness and autoimmune conditions — both contribute to and result from increased permeability

Most people with leaky gut have multiple contributing factors. Healing requires addressing the inputs, not just adding repair ingredients on top of an unchanged environment.

Signs and symptoms (with the usual caveat)

The honest framing is that leaky gut symptoms are non-specific — they overlap heavily with IBS, SIBO, food sensitivities, and dysbiosis. None of these alone confirms increased permeability. But common symptom patterns include:

Persistent digestive symptoms: bloating, gas, alternating constipation and diarrhea, food sensitivities that seem to be increasing
New or worsening food intolerances (particularly gluten, dairy, and FODMAPs)
Skin issues: eczema flares, acne that doesn’t respond to topical treatment, unexplained hives
Joint pain or stiffness without an obvious cause
Brain fog, fatigue, mood changes that track with digestive symptoms
Autoimmune flares (in those already diagnosed)
Histamine intolerance (flushing, itching, headaches after fermented or aged foods)

If you have any of these consistently, it’s worth talking to a qualified practitioner. A functional medicine physician, integrative-medicine MD, or gastroenterologist familiar with the research can order appropriate testing (lactulose-mannitol challenge is the most reliable; zonulin blood tests are still imperfect but used) and rule out other causes.

The repair framework: what actually works

Functional medicine has a useful framework called the 5R Protocol: Remove, Replace, Reinoculate, Repair, Rebalance. The order matters — you can’t effectively rebuild a structure while the things damaging it are still in place.

1. Remove the triggers

This is the most important step and the one most often skipped. For 60–90 days, remove or significantly reduce:

Gluten and refined grains
Refined sugar and ultra-processed food
Industrial seed oils
Alcohol
NSAIDs (only if your physician approves alternative pain management)
Foods you’ve identified as personal triggers

If SIBO or parasites are part of your picture, those need to be addressed first or in parallel. A gut lining repair protocol layered on top of an active overgrowth typically yields disappointing results.

2. Replace what supports digestion

If digestive enzymes or stomach acid are low (common with chronic stress, certain medications, or age), they may need to be supported during the repair window. Apple cider vinegar before meals, bitters, or a digestive enzyme supplement can help. This is most relevant if you experience heavy fullness, undigested food in stool, or B12 deficiency on bloodwork.

3. Reinoculate beneficial bacteria

The microbiome and the intestinal barrier are deeply interdependent — healthy commensal bacteria produce short-chain fatty acids (especially butyrate) that directly nourish the cells of the intestinal lining. Reinoculation can come from:

A high-quality probiotic (multi-strain, with documented strain identity, ideally including Lactobacillus rhamnosus, Bifidobacterium lactis, and a Saccharomyces species)
Fermented foods if tolerated (sauerkraut, kimchi, kefir, plain yogurt) — though some people with histamine intolerance need to defer these
Prebiotic fibers (modest amounts of inulin, FOS, partially hydrolyzed guar gum) to feed the bacteria you’re reintroducing

4. Repair the gut lining

This is where targeted nutrients and herbs come in. The strongest evidence:

L-Glutamine — the primary fuel source for enterocytes (intestinal cells). A 2024 meta-analysis confirmed glutamine supplementation reduced intestinal permeability in clinical trials, particularly at higher doses (Glutamine supplementation on gut permeability: a systematic review and meta-analysis. PMC, 2024). Mechanistically, glutamine supports tight junction protein expression, reduces pro-inflammatory cytokines, and provides direct fuel for the rapidly-turning-over cells of the intestinal lining (Glutamine and the regulation of intestinal permeability. PubMed, 2017).
Mucilaginous herbs — aloe vera leaf, marshmallow root, and slippery elm form a soothing protective coating over the intestinal lining and reduce inflammation. These have centuries of traditional use and reasonable preclinical support.
Quercetin — a flavonoid antioxidant that stabilizes mast cells and supports inflammatory balance in the gut. Useful for people with histamine-related symptoms.
Triphala — a traditional Ayurvedic three-fruit formula with documented support for gut microbial balance, motility, and barrier function in preclinical research.
Zinc carnosine — well-studied for stomach lining support, with some evidence extending to lower-GI repair.

5. Rebalance lifestyle factors

The most underrated step. Sleep, stress management, regular movement, and time in nature all directly affect gut barrier function via the gut-brain axis. Eight hours of good sleep does more for your gut than most supplements. Daily walking does more than expensive probiotics if you’re skipping the basics.

How the Luna Lab Gut Lining Reset is built

Our Gut Lining Reset is designed around the “Repair” and “Reinoculate” pillars of the 5R framework. It’s a 60–90 day protocol — longer than the parasite cleanse, because cell-level intestinal repair takes time. Cells lining the gut renew approximately every 3–5 days, but the structural and microbiome changes that loosen the barrier in the first place take weeks to months to fully reverse.

The formula combines, in a single daily pack:

Gut Repair & Strengthening: L-Glutamine (the primary repair amino acid for enterocytes) and Triphala (for microbial balance and digestive motility)
Microbiome Balance: A vegan 10-billion-CFU probiotic blend with documented strains, plus prebiotics and digestive enzymes
Soothing & Comfort: A fiber blend of aloe, marshmallow, and slippery elm that gently soothes the intestinal lining; plus Quercetin for antioxidant and inflammatory support

The protocol is simple: one pack per day in the morning, 10 minutes before your first meal, for 60–90 days. We pair it with the same dietary framework outlined above, the same baseline of cGMP-certified manufacturing in NSF International facilities, 90+ quality checkpoints, and our same founder-owned commitment to quality over margin.

Note: if parasitic burden or significant SIBO is part of your picture, we typically recommend addressing those first — with our Herbal Cleanse Formula or Microbiome Balance Formula — then following with the Gut Lining Reset to repair what the overgrowth disturbed. This sequencing is consistent with the “Remove first” principle.

Frequently asked questions

How long does it take to heal leaky gut?

Realistic expectations: noticeable symptom improvement in 4–6 weeks; meaningful structural repair across 60–90 days of consistent support; full restoration of gut microbiome diversity often longer (6+ months) depending on starting point and adherence. Anyone promising 7-day or 14-day “leaky gut healing” is overpromising.

Should I get tested for leaky gut?

If you have specific symptoms or autoimmune disease, yes — through a functional medicine practitioner. The lactulose-mannitol test is the most reliable; commercial zonulin blood tests have specificity concerns and should be interpreted alongside symptoms and clinical context, not as a standalone diagnostic.

Do I have to remove gluten forever?

No, unless you have celiac disease (in which case yes, lifelong). For non-celiac gluten sensitivity, many people tolerate occasional gluten after their gut heals. Strict avoidance during the 60–90 day repair window is the standard approach; reintroduction can be tested afterward with attention to symptoms.

Can I do the parasite cleanse and gut lining reset at the same time?

We recommend doing them in sequence rather than simultaneously: parasite cleanse first (30 days), then a brief gap of 1–2 weeks, then the Gut Lining Reset (60–90 days). The parasite formula creates some disturbance the lining repair protocol then addresses. Doing them simultaneously dilutes both.

Can I take the Gut Lining Reset with prescription medications?

Talk to your doctor first. Most people can — with timing adjusted to take medications 2–3 hours apart from the supplement — but specific drug interactions need to be reviewed individually. The most common interactions to watch for are with immunosuppressants, anticoagulants, and certain heartburn medications.

Will this work if I keep eating processed food and drinking alcohol?

Honest answer: less well. The supplement provides repair raw materials, but if you’re continually re-injuring the lining, you’re bailing water out of a leaky boat without patching it. The diet shift is at least as important as the supplement.