What Is Leaky Gut Syndrome?
Written by 
Dr. Michael Ruscio, DC on
May 23, 2025
Written by
Dr. Michael Ruscio, DC on May 23, 2025
—
Reviewed by 
Hilary Watts
What Is Leaky Gut?
The cells lining your small intestine are connected by tight junctions, special proteins that act like gatekeepers. They carefully regulate what passes from your digestive tract into your bloodstream—allowing nutrients through while keeping out larger, potentially harmful substances.
When these tight junctions become overly permeable—a condition often referred to as “increased intestinal permeability” or “leaky gut”—larger molecules such as partially digested food, microbial fragments, and toxins may cross the intestinal barrier.
The immune system, seeing these unfamiliar particles in the bloodstream, flags them as threats and mounts an immune response.
Over time, repeated exposure to these triggers can lead to chronic, low-grade inflammation that affects the entire body. This has been associated with a range of conditions, from digestive disorders to autoimmune diseases.
The Leaky Gut-Inflammation Cycle
Leaky gut and inflammation can become an ongoing cycle. Let’s look more closely at the leaky-gut inflammation cycle.
First, it’s important to be familiar with a protein called zonulin.
Zonulin plays a part in both the cause and effect of a leaky gut. Zonulin regulates tight junctions—the gatekeepers between the small intestine barrier and the bloodstream—and increases intestinal permeability 1.
Zonulin is also a marker of inflammation. When zonulin levels are high, it may indicate that inflammation is high 1.
When a leaky gut occurs, the body may produce more zonulin as an effort to fix the problem and protect the small intestine 2. This increase in zonulin may then further increase intestinal permeability, which can ramp up inflammation, and then lead to the creation of more zonulin 3.
So, we know zonulin plays a role in a leaky gut. But what causes this inflammation-leaky gut cycle to begin in the first place?
What Causes a Leaky Gut?
Although the exact cause of a leaky gut—also known as increased intestinal permeability—is still uncertain, it’s best understood as a warning sign. Think of it like a dashboard light blinking on in your car: It doesn’t tell you exactly what’s wrong, but it signals that something in the system is off. In this case, it’s your gut lining alerting you to possible imbalance or ongoing stress in the body.
A number of everyday stressors can damage or weaken the gut barrier. These include:
- Inflammation from infections or chronic diseases 4
- Frequent consumption of ultra-processed foods, which often lack fiber and are high in additives and preservatives 5
- Alcohol intake, which, even in moderate amounts, can compromise gut integrity 6
- Diets high in saturated fats, which may promote inflammation and alter the gut microbiome 7
- Chronic psychological stress, which affects gut function via the gut-brain axis 8
- Poor sleep quality, which, especially when persistent, disrupts circadian rhythms that regulate gut health 9
- Overuse of NSAIDs (like ibuprofen or naproxen), which are known to erode the protective gut lining 10
What complicates things further is the chicken-and-egg nature of a leaky gut and many chronic conditions. We don’t yet know whether a leaky gut is a cause or a consequence—or a bit of both—when it comes to conditions like:
- Irritable bowel syndrome (IBS) 11 12
- Inflammatory bowel disease (IBD) 13
- Celiac disease 14
- Small intestinal bacterial overgrowth (SIBO) 15
- Dysbiosis, or an unhealthy gut microbiome 16
- Mild cognitive impairment and Alzheimer’s disease 17
- Rheumatoid arthritis 18
Still, the associations between these conditions and increased intestinal permeability are well-documented. This is why many functional and integrative health practitioners focus on healing the gut first: When the gut lining is repaired and inflammation is reduced, symptoms across a wide range of these seemingly unrelated conditions often improve. The gut, in essence, serves as a central hub for overall health—and when it’s compromised, the ripple effects can be felt throughout the entire body.
Symptoms of a Leaky Gut
Leaky gut syndrome may cause a wide variety of symptoms across many different body systems. Based on our experience in the clinic and the existing research, here are some signs you may have a leaky gut:
- Gas and bloating
- Constipation or diarrhea
- Reflux or heartburn 19
- Symptoms of digestive disorders like IBS, IBD, celiac disease, or SIBO
- Depression 20
- Fatigue 21
- Joint pain 18
- Poor sleep 16 22
- Weight gain 23
- Allergies 24
How to Know If You Have a Leaky Gut
If you’re wondering whether you have a leaky gut, you’re not alone—and unfortunately, you also won’t get a straight answer from most medical tests. There’s no single gold-standard test for leaky gut, and many of the tests marketed for it are plagued by questionable reliability, inconsistent standards, or unclear clinical meaning.
Here’s where things stand:
- Zonulin testing is biologically relevant but poorly standardized 25.
- Leaky gut antibody panels are intriguing but don’t line up with symptoms 26.
- Lactulose/mannitol testing offers the clearest biological insight but is not standardized and cumbersome to use 14.
- Stool tests are not credible sources for assessing leaky gut.
If you suspect a leaky gut, clinical judgment still matters most. I highly recommend working with someone who considers your symptoms, lifestyle, known diagnoses, and risk factors. Testing may offer supporting evidence—but it shouldn’t be your sole compass.
Is Leaky Gut the Cause of Autoimmune Diseases?
Many in the alternative medicine community claim that leaky gut is the root cause of all autoimmune diseases.
While there is some evidence to suggest an association between a leaky gut and some autoimmune diseases, there is not yet enough evidence to say that autoimmune disease is caused by leaky gut.
Some studies suggest certain autoimmune diseases may be triggered by increased intestinal permeability.
- In one study, Crohn’s disease patients and their close relatives were evaluated for intestinal permeability. The relatives showed evidence of increased intestinal permeability, even though they did not have any symptoms of Crohn’s disease, indicating that a leaky gut may precede the development of Crohn’s intestinal symptoms 27.
- In human and animal studies, intestinal permeability has occurred before the development of disease 28.
More research is needed to fully understand these and related phenomena. But the bottom line is that there is not currently enough evidence to suggest that autoimmune disease is caused by a leaky gut.
How to Improve a Leaky Gut
Whether you have an autoimmune disease, chronic inflammation, or are experiencing frustrating symptoms, there is plenty you can do to improve your gut health and repair a leaky gut.
Diet Changes
The first step in healing a leaky gut is changing an inflammatory diet. Think of it this way—if a skincare product started to give you a rash, you wouldn’t just slap on cortisone cream and keep using it—you would find a better product!
It’s much the same with diet. If you continue to eat foods that trigger inflammation or sensitivities, you’re only making the problem worse. Improving your diet is one of the most important steps you can take for gut health.
Several anti-inflammatory diets are great starting points for building a leaky gut diet plan. There is no right leaky gut diet. Instead, the best one is the one that works for you.
Here is a summary of the diets with evidence suggesting they may help improve intestinal permeability:
| Diet | How It May Heal Leaky Gut |
| Low FODMAP diet | Reduces gut irritants and may help decrease bacterial toxins and zonulin 29 |
| Mediterranean diet | Provides a wide array of nutrients, which may reduce bacterial toxins and zonulin while increasing short-chain fatty acids and omega-3 fatty acids 30 |
| Gluten-free diet | In people with non-celiac gluten sensitivity, it may decrease zonulin, GI symptoms, fatigue, anxiety, and joint pain 31 |
Working with a nutritionist may help you find the right diet to use faster. You can also learn how to create your own leaky gut diet.
Habit Changes
Simple changes to your daily habits may significantly improve a leaky gut. You don’t necessarily need to do ALL these things to experience a benefit. Chances are you’ll discover that just a couple of these evidence-based options are most out of balance.
| Habit Change | Why It’s Important |
| Regular moderate exercise | Exercise can help heal a leaky gut, especially if it’s moderate and lasts less than an hour. But if you push too hard or work out for over an hour, it can actually make things worse 32. |
| Increase nightly hours of sleep | Sleeping well may help prevent a leaky gut 9. |
| Improve your stress management | Managing stress is key to keeping your gut healthy. Things like mindfulness can reduce inflammation and boost your immune system, which helps prevent or heal a leaky gut 33. |
| Reduce alcohol consumption | Alcohol consumption can compromise the gut wall 6. |
| Use alternatives to NSAIDs and aspirin | Research clearly demonstrates that NSAIDs and aspirin can increase intestinal lining damage and leaky gut 10. |
| Consider alternatives to birth control pills for contraception | People who take oral contraceptives (birth control pills) may tend to have higher gut permeability than those with natural menstrual cycles and men 34. |
Supplements to Heal a Leaky Gut
Many supplements claim to support gut health, but only a few stand out for their consistent benefits in both clinical research and practice. Based on the latest evidence and what I’ve seen work for my clients, here are five of the most effective supplements for gut barrier integrity and overall digestive health:
- Probiotics, especially blends with Lactobacillus and Bifidobacterium, can lower inflammation, reduce harmful bacterial toxins, and support healthy gut bacteria 35 36.
- Bovine colostrum looks promising—about 80% of studies in a review showed it helped improve a leaky gut 37.
- Immunoglobulins have been shown to reduce gut leakiness and inflammation; in one high-quality study, HIV patients who took them for 6 months saw clear benefits 38.
- Glutamine can strengthen the gut lining and ease symptoms. One study found it helped 80% of people feel better 39.
- Zinc may help strengthen the gut lining by increasing tight junction proteins 40. One study found that people who did intense exercise had a 3-fold increase in gut permeability. But after taking zinc carnosine for 14 days, that increase was reduced by 70% 41. Though supplements can help, the best way to get zinc is through food sources like oysters, beef, crab, oats, pumpkin seeds, pork, lentils, and sardines 42.
With so many gut health products out there, it’s hard to know what really works. And juggling five or more different supplements can be both costly and overwhelming. That’s why—after seeing how often my clients struggled with this—my team and I decided to develop our own versions of the most effective options, including:
You Can Repair a Leaky Gut
Leaky gut, a loosening of the tight junctions between the cells of the small intestine, may sound a bit complicated. But the simple truth is that eating well, maintaining good health habits with sleep, stress, and exercise, and a few key supplements can help restore your intestinal wall barrier. Repairing a leaky gut is entirely possible, and many of my clients see rapid symptom improvement within a matter of weeks.
Though there isn’t yet enough evidence to claim that all autoimmune diseases are caused by leaky gut syndrome, we do know that many medical conditions and distressing symptoms can be improved by taking a few simple steps to improve gut health.
If you need help healing a leaky gut, check out my comprehensive gut-healing protocol in Healthy Gut, Healthy You, or reach out to us at the clinic.
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Dr. Michael Ruscio is a DC, natural health provider, researcher, and clinician. He serves as an Adjunct Professor at the University of Bridgeport and has published numerous papers in scientific journals as well as the book Healthy Gut, Healthy You. He also founded the Ruscio Institute of Functional Health, where he helps patients with a wide range of GI conditions and serves as the Head of Research.➕ References
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