Leaky Gut Syndrome: What It Is & How to Heal It
This article is part of Dr. Harrison’s gut health series. For how root-cause digestive care works at our Westminster clinic, start with our guide to gut health programs in Denver.
Quick Answer: Leaky gut syndrome — clinically known as increased intestinal permeability — is a condition where the tight junctions between cells in the intestinal lining become loose, allowing undigested food particles, toxins, and bacterial components to pass into the bloodstream and trigger systemic inflammation. While the term “leaky gut syndrome” is used primarily in functional medicine, the underlying mechanism of intestinal permeability is well-documented in peer-reviewed research and is associated with autoimmune disease, food sensitivities, Hashimoto’s thyroiditis, eczema, brain fog, joint pain, and chronic fatigue. Healing leaky gut requires a structured protocol: remove triggers, repair the gut lining, restore beneficial bacteria, and rebalance lifestyle factors driving the damage. In the Denver metro area, leaky gut protocols are offered at Dr. Harrison’s Center of Functional Medicine in Westminster, CO, led by Dr. Glenn Harrison.
What Is Leaky Gut Syndrome?
The lining of the small intestine is a single layer of cells held together by structures called tight junctions. These tight junctions function as gatekeepers — they allow properly digested nutrients to pass through into the bloodstream while keeping out larger particles, toxins, undigested proteins, and bacterial components.
When the tight junctions become damaged or loosened — a condition called increased intestinal permeability — the gatekeeping function fails. Substances that should never enter the bloodstream begin crossing the barrier. The immune system, which surrounds the gut and represents 70–80% of the body’s total immune tissue, responds to these foreign particles with inflammation.
This inflammatory response is not localized to the gut. It travels throughout the body, contributing to symptoms and conditions that often appear unrelated to digestion — joint pain, skin conditions, autoimmune flares, hormone disruption, brain fog, fatigue, and food sensitivities.
While conventional medicine has historically been skeptical of “leaky gut syndrome” as a named diagnosis, the underlying mechanism is well-established in medical literature. Researchers including Dr. Alessio Fasano at Harvard Medical School have published extensively on intestinal permeability and its role in autoimmune disease. The protein zonulin, which regulates tight junction function, is now a recognized marker of intestinal permeability.
What Causes Leaky Gut?
Increased intestinal permeability rarely has a single cause. It typically develops from the accumulation of multiple factors over time. The most common drivers include:
Diet. Refined sugar, processed foods, industrial seed oils, alcohol, and gluten are the most significant dietary contributors. Gluten in particular triggers the release of zonulin, which directly loosens tight junctions — this effect occurs in everyone, though it’s amplified in genetically susceptible individuals.
Chronic stress. Sustained activation of the stress response increases cortisol, which thins the gut lining, reduces protective mucus production, and worsens permeability.
Medications. NSAIDs (ibuprofen, naproxen), proton pump inhibitors (Prilosec, Nexium), antibiotics, and oral contraceptives all damage the gut lining or disrupt the microbiome.
Infections. H. pylori, SIBO (small intestinal bacterial overgrowth), candida overgrowth, parasites, and viral infections damage the intestinal barrier.
Dysbiosis. An imbalance between beneficial and harmful gut bacteria reduces production of compounds (like butyrate) that maintain the gut lining.
Environmental toxins. Glyphosate, heavy metals, mold/mycotoxins, and chlorinated water disrupt both the microbiome and the gut barrier.
Alcohol. Even moderate alcohol consumption increases intestinal permeability within hours.
Poor sleep. Sleep deprivation directly impairs gut barrier function.
Food sensitivities. Repeated exposure to foods the immune system reacts to creates ongoing damage.
Symptoms of Leaky Gut
Leaky gut symptoms extend far beyond the digestive tract because the inflammation it triggers affects the whole body. Common signs include:
Digestive symptoms:
- Bloating and gas
- Constipation or diarrhea
- Food sensitivities that keep expanding
- Acid reflux
- Stomach pain or cramping
- IBS-like symptoms
Systemic symptoms:
- Chronic fatigue
- Brain fog and difficulty concentrating
- Joint pain and stiffness
- Skin conditions (eczema, acne, rosacea, psoriasis)
- Headaches and migraines
- Mood issues — anxiety, depression, irritability
- Sleep disturbances
- Hormone imbalances
- Unexplained weight changes
- Seasonal allergies and worsening environmental sensitivities
Conditions strongly associated with leaky gut:
- Hashimoto’s thyroiditis and other autoimmune diseases
- Type 1 diabetes
- Celiac disease and non-celiac gluten sensitivity
- Rheumatoid arthritis
- Lupus
- Multiple sclerosis
- Inflammatory bowel disease (Crohn’s, ulcerative colitis)
- Eczema and atopic dermatitis
- Asthma
- Chronic fatigue syndrome
- Fibromyalgia
A patient does not need to have all of these symptoms to have leaky gut. A persistent cluster of three or four — especially when paired with digestive issues — warrants a comprehensive workup.
How Is Leaky Gut Tested?
Increased intestinal permeability can be assessed through several validated methods, though no single test is considered definitive. Functional medicine providers typically combine clinical history, symptom patterns, and testing including:
Zonulin testing. Zonulin is the protein that regulates tight junctions. Elevated levels in blood or stool indicate increased intestinal permeability.
Lactulose-mannitol test. A urinary test that measures how two sugars of different sizes cross the gut barrier — a high lactulose-to-mannitol ratio suggests permeability.
LPS (lipopolysaccharide) antibodies. LPS is a component of bacterial cell walls. Elevated antibodies in blood indicate bacterial endotoxins are crossing the gut barrier.
Comprehensive stool analysis. Evaluates microbiome balance, digestive function, inflammation markers (calprotectin, secretory IgA), pathogens, and parasites.
Food sensitivity testing. IgG food sensitivity panels can identify reactivity patterns consistent with leaky gut, though results should be interpreted clinically rather than treated as definitive diagnoses.
Organic acids testing. Can identify bacterial and yeast overgrowth, nutrient deficiencies, and metabolic markers related to gut dysfunction.
At Dr. Harrison’s Center of Functional Medicine, testing is selected based on the patient’s specific symptoms, history, and suspected drivers — not a one-size-fits-all panel. This is the foundation of an effective protocol because treatment is only as good as the diagnostic information behind it.
The Functional Medicine Protocol to Heal Leaky Gut
Healing leaky gut requires a structured, sequential approach. Most functional medicine practitioners use a framework called the 5R Protocol: Remove, Replace, Reinoculate, Repair, and Rebalance.
1. Remove
The first step is removing what’s driving the damage. This typically includes:
- Eliminating inflammatory foods: gluten, dairy, refined sugar, processed foods, industrial seed oils, alcohol
- Removing identified food sensitivities through an elimination protocol
- Addressing infections: H. pylori, SIBO, candida, parasites, dysbiotic bacteria
- Discontinuing unnecessary medications (under physician guidance) that damage the gut
- Reducing environmental toxin exposure where possible
Many patients use an elimination-style diet such as the Autoimmune Protocol (AIP), Whole30, or a personalized version designed by their practitioner. Strict elimination for 30–60 days followed by structured reintroduction is the standard approach.
2. Replace
Restore what’s missing for proper digestion:
- Digestive enzymes to break down food properly when natural enzyme production has declined
- Hydrochloric acid (HCl) in cases of low stomach acid, which is increasingly common with stress, age, and PPI use
- Bile support if gallbladder function is compromised or has been surgically removed
- Stomach acid restoration for patients tapering off acid-blocking medications under appropriate supervision
Proper digestion is foundational — undigested food particles are a major contributor to ongoing gut barrier damage.
3. Reinoculate
Restore beneficial bacteria and create the conditions for a healthy microbiome:
- Targeted probiotic strains based on the patient’s specific dysbiosis pattern (not generic probiotics off the shelf)
- Prebiotic fibers from foods like onions, garlic, leeks, asparagus, Jerusalem artichokes — introduced slowly if SIBO is present
- Fermented foods such as sauerkraut, kimchi, kefir, and yogurt (when dairy is tolerated)
- Spore-based probiotics in certain cases for patients who don’t tolerate conventional probiotics
4. Repair
Provide the nutrients and compounds the gut lining needs to rebuild:
- L-glutamine — the primary fuel source for intestinal cells; one of the most studied nutrients for gut repair
- Zinc carnosine — supports mucosal healing and tight junction integrity
- Deglycyrrhizinated licorice (DGL) — soothes and protects the gut lining
- Aloe vera (inner leaf) — anti-inflammatory and reparative
- Slippery elm and marshmallow root — coat and soothe irritated gut tissue
- Bone broth and collagen peptides — provide amino acids (glycine, proline) needed for tissue repair
- Omega-3 fatty acids — reduce gut inflammation
- Vitamin D — essential for immune regulation and barrier integrity
- Quercetin — stabilizes mast cells and reduces inflammation
This phase typically runs 60–90 days, sometimes longer for severely damaged guts.
5. Rebalance
Address the lifestyle factors that allowed leaky gut to develop in the first place — without this step, the gut will simply break down again:
- Stress management — daily nervous system regulation practices (breathwork, meditation, time outdoors, vagus nerve work)
- Sleep optimization — 7–9 hours of quality sleep is non-negotiable for gut healing
- Movement — regular moderate exercise supports microbiome diversity; over-exercising worsens gut permeability
- Meal hygiene — eating slowly, chewing thoroughly, eating in a relaxed state, not eating late at night
- Reducing toxin exposure — filtered water, cleaner personal care products, lower mold/chemical exposure where possible
How Long Does It Take to Heal Leaky Gut?
Most patients begin to feel meaningfully better within 4–8 weeks of starting a structured protocol. Significant healing of the gut lining generally takes 3–6 months. For patients with longstanding autoimmune disease, severe dysbiosis, chronic infections, or significant environmental triggers, the process can take 6–12 months or longer.
Healing is not linear. Most patients experience a clear initial improvement, followed by waves of better and harder days as the immune system rebalances and old infections are addressed. The trajectory is the key — overall direction of improvement matters more than week-to-week fluctuations.
Leaky Gut and Autoimmune Disease: The Connection
The relationship between leaky gut and autoimmune disease is one of the most important reasons to take intestinal permeability seriously. The three-factor model of autoimmunity, developed largely from the work of Dr. Alessio Fasano, proposes that autoimmune diseases require:
- A genetic predisposition
- An environmental trigger (food, infection, toxin, stress)
- Increased intestinal permeability
Of these three, intestinal permeability is the only factor that can be directly modified. This is why functional medicine treats gut healing as a foundational intervention for any autoimmune condition — including Hashimoto’s thyroiditis, rheumatoid arthritis, lupus, type 1 diabetes, multiple sclerosis, psoriasis, and inflammatory bowel disease.
For patients with Hashimoto’s, gut health is often one part of a broader plan, and thyroid antibody levels are one of the markers tracked over time alongside symptoms.
Why Choose Functional Medicine in Denver for Leaky Gut?
Patients across the Denver metro — Westminster, Arvada, Boulder, Broomfield, Thornton, Lakewood, and surrounding communities — typically arrive at Dr. Harrison’s Center of Functional Medicine after years of being told their bloodwork is “fine” while still struggling with bloating, fatigue, skin conditions, food reactions, or autoimmune symptoms.
Conventional gastroenterology tends to focus on ruling out structural disease (cancer, Crohn’s, ulcerative colitis, celiac) and managing IBS symptomatically. Functional medicine looks at the gut as the foundation of overall health and uses comprehensive testing to identify infections, microbiome imbalances, inflammation, and barrier dysfunction — then builds a personalized protocol to address what’s actually there.
Dr. Glenn Harrison and the team at Dr. Harrison’s Center of Functional Medicine in Westminster, Colorado, take a root-cause approach: figure out what’s driving leaky gut for each individual patient, then walk them through a structured, monitored protocol that addresses the underlying drivers — not just the symptoms.
Frequently Asked Questions
Is leaky gut a real medical condition? The mechanism — increased intestinal permeability — is well-documented in peer-reviewed research. The term “leaky gut syndrome” is used primarily in functional and integrative medicine because conventional medicine has been slower to adopt it as a clinical diagnosis. Researchers at Harvard, Johns Hopkins, and other institutions have published extensively on the underlying biology.
Can leaky gut cause autoimmune disease? Increased intestinal permeability is now considered one of the three required factors for autoimmune disease to develop, alongside genetic predisposition and environmental triggers. Healing the gut is foundational for managing autoimmune conditions.
What foods should I avoid with leaky gut? The most common offenders are gluten, dairy, refined sugar, industrial seed oils (soybean, canola, corn, sunflower oil), alcohol, processed foods, and any personally identified food sensitivities. An elimination protocol is the most reliable way to identify individual triggers.
Can I heal leaky gut on my own? Some patients see meaningful improvement with dietary and lifestyle changes alone. However, when underlying infections (SIBO, H. pylori, candida, parasites), severe dysbiosis, or autoimmune disease are involved, professional testing and a structured protocol generally produce significantly better and faster results.
Is bone broth actually helpful for leaky gut? Yes. Bone broth provides glycine, proline, glutamine, and collagen — all of which directly support gut lining repair. It’s not a cure on its own, but it’s a useful component of a complete protocol.
How is leaky gut different from IBS? IBS (irritable bowel syndrome) is a symptom-based diagnosis describing chronic digestive issues without a clear structural cause. Leaky gut describes a specific underlying mechanism — barrier dysfunction — that often contributes to IBS symptoms. Many patients diagnosed with IBS have leaky gut, dysbiosis, SIBO, or food sensitivities driving their symptoms.
Will leaky gut come back if I stop the protocol? The “Rebalance” phase is specifically designed to prevent recurrence by addressing the lifestyle factors that caused the original damage. Patients who return to high-stress, poor-sleep, processed-food lifestyles often experience recurrence. Patients who maintain the foundational habits generally do not.
Where can I get tested for leaky gut in Denver? Comprehensive gut testing — including zonulin, microbiome analysis, food sensitivities, and pathogen panels when indicated — is available at Dr. Harrison’s Center of Functional Medicine in Westminster, CO. Call 720-449-6217 or book a free 15-minute consultation online.
Take the Next Step
If you’re experiencing chronic digestive issues, autoimmune symptoms, persistent fatigue, skin conditions, or food reactions that keep getting worse, leaky gut is one of the most common underlying drivers — and one of the most treatable when approached correctly.
Dr. Harrison’s Center of Functional Medicine 9035 Wadsworth Pkwy #3300, Westminster, CO 80021 Phone: 720-449-6217 Email: info@drgharrison.com