Leaky Gut — What It Is and How to Repair It

Clinically informed by Megan Pennington, BSc, CLT — Integrative Health Practitioner & Certified LEAP Therapist, MP Integrative Health

Here’s what it actually is, what causes it, how it drives chronic symptoms, and — most importantly — what the repair process looks like in practice.

What leaky gut actually means

The gut lining is a single cell layer thick — one of the most remarkable structural facts in human biology. Those cells are held together by proteins called tight junctions, which act as gatekeepers: selectively allowing nutrients, water, and electrolytes through while blocking bacteria, undigested food proteins, and inflammatory compounds.

When tight junctions are compromised — from any of a number of causes — this selectivity breaks down. Larger molecules that should stay in the gut pass through into systemic circulation. The immune system, encountering these foreign compounds in the bloodstream, mounts responses. Inflammation spreads beyond the gut. Immune reactivity increases over time.

This is intestinal permeability — or, informally, leaky gut. It isn’t a single event; it’s an ongoing condition that worsens as long as the causative factors persist.

What causes leaky gut

The most common drivers we see in practice:

• Food sensitivities: reactive foods trigger inflammation at the gut wall directly, degrading tight junction integrity over time
• Gut dysbiosis: imbalanced microbiome composition, including bacterial overgrowth, reduces production of short-chain fatty acids that maintain epithelial integrity
• Chronic stress: cortisol and stress hormones directly increase intestinal permeability — this is a documented biological mechanism, not a metaphor
• NSAIDs and antibiotics: both disrupt the gut lining and microbiome in ways that contribute to permeability, particularly with repeated use
• Alcohol: directly dissolves tight junction proteins with regular consumption
• Low-fibre diet: starves the beneficial bacteria that produce the butyrate maintaining epithelial cell health
• Infections: viral and bacterial gut infections can initiate or accelerate permeability, and post-viral gut dysfunction is increasingly recognised as a significant contributor

What leaky gut drives

When bacterial endotoxins (lipopolysaccharides, or LPS) and food proteins enter systemic circulation through a permeable gut, the immune system responds — and that response doesn’t stay local. Systemic immune activation from leaky gut contributes to:

• Chronic fatigue and brain fog (inflammatory cytokines cross the blood-brain barrier)
• Food sensitivities (repeated exposure of the immune system to food proteins in circulation drives sensitisation)
• Autoimmune conditions (molecular mimicry between food proteins and host tissue triggers cross-reactive immune responses)
• Skin conditions including eczema, psoriasis, and rosacea (gut-skin axis)
• Joint pain and inflammatory arthritis
• Mood disruption and anxiety (gut-brain axis disruption)
• Hormonal imbalance (gut inflammation affects estrogen metabolism and thyroid hormone conversion)

How to repair leaky gut: the staged approach

Gut repair is not a single supplement or a one-month protocol. It is a staged process that requires removing the triggers before repair can begin. Attempting to repair the gut while the primary inflammatory driver is still active is like patching a hole in a boat that’s still sinking.

Stage 1 — Remove the triggers

The first and most impactful step is identifying and eliminating the foods driving gut inflammation. MRT testing identifies your specific reactive foods — not based on generic elimination lists, but on your individual immune response. The LEAP Protocol then builds your initial diet exclusively from your safest foods, rapidly reducing the inflammatory load at the gut wall. Most clients notice improvement in digestive symptoms within the first 7–10 days of this phase.

Stage 2 — Repair the mucosal lining

Once triggers are removed, targeted nutritional support accelerates structural repair:

Stage 3 — Restore the microbiome

A diverse, balanced microbiome is essential for maintaining gut barrier integrity long-term. Beneficial bacteria produce butyrate — the primary energy source for colonocytes and a key regulator of tight junction function. Microbiome restoration requires:

• Strain-specific probiotic supplementation (not all strains are equivalent — clinical context matters)
• Prebiotic fibre to feed beneficial bacteria: leeks, asparagus, garlic, Jerusalem artichoke, chicory
• Fermented foods as tolerated: kefir, sauerkraut, kimchi, unsweetened yogurt

An important note: probiotics are significantly more effective once reactive foods have been removed. Adding probiotics to a gut still under active inflammatory assault from food triggers produces limited results. The sequencing of Stage 1 before Stage 3 is not optional — it’s what determines whether the investment in gut restoration actually works.

Stage 4 — Address the nervous system

Chronic stress independently increases intestinal permeability through cortisol-driven tight junction disruption. Gut repair protocols that don’t address the stress physiology driving permeability will produce incomplete results. Practices that restore vagal tone — diaphragmatic breathing, mindfulness, gentle movement, sufficient sleep — are a biological necessity in this process, not optional wellness additions.

How long does gut repair take?

Gut epithelial cells turn over every 3–5 days — meaning structural repair begins almost immediately once triggers are removed. Meaningful barrier restoration typically takes 4–8 weeks of consistent effort. Full microbiome rebalancing takes 3–6 months. The reassuring reality: most clients feel significantly better well before the structural healing is complete, because reducing the inflammatory load produces symptomatic improvement rapidly.