What is Leaky Gut?

We admit, it sounds kind of gross and in reality, it really is. “Leaky gut” is the more colloquial term that means intestinal permeability (IP). The intestines are much more than just a chute for stool to pass through and out. They are essential to the process of withdrawing and absorbing nutrients and water from the chyme (what consumed food/beverages become at this stage) into the bloodstream for distribution and use.

The intestinal walls feature tiny openings that allow for this absorption to occur while also being small enough to keep out the irrelevant, useless and potentially harmful substances in the chyme. Leaky gut is the instance in which these pores become larger and wider, allowing larger particles, hitchhiking bacteria, and toxins to enter the bloodstream.

You won’t directly or acutely feel this happening in the body, but you assuredly will feel the results of intestinal permeability. According to research, leaky gut may be a significant contributing factor to development of food allergies and sensitivities, celiac disease, Crohn’s disease and irritable bowel syndrome, as well as diabetes and polycystic ovarian syndrome. This condition is also strongly linked to autoimmune disease (eg, psoriasis and non-alcoholic cirrhosis).

Further, another review discussed evidence that leaky gut is complicit in causing anxiety and depression, both of which are linked to gut imbalance and inflammation, and that this may impair the gut-brain axis (GBA), as “healthy gut function has been liked to normal central nervous system function.

In one paper, researchers emphasized, “the severity of IP appears to be exacerbated by the presence of dysbiosis, inflammation and glucose metabolism disorders,” suggesting that gut microbiota imbalance is a culprit in causing leaky gut.

If you are wondering if you are dealing with intestinal permeability absent any diagnosis of anxiety, depression, diabetes, etc., there may be some signs that you have a leaky gut. These include frequent bouts of diarrhea, constipation, flatulence/bloating, fatigue, headaches, skin conditions (eg, eczema, acne), joint discomfort, and foggy brain (difficulty concentrating).

Causes and risk factors for developing and/or exacerbating intestinal permeability are both controllable and uncontrollable. Causative factors you can control are diet, alcohol intake, tobacco use and to a lesser degree, stress. Factors you cannot control are autoimmune disorders, infections and diabetes (although you can better manage the state of the latter through diet and supplementation). Another factor that you can control to a large extent is creating favorable gut microbe balance: reducing dysbiosis.

A healthy gut lumen (the interior) comes into contact with toxins, antigens and a wide variety of microorganisms. The lining of the tubular interior of the intestines is known as the epithelium, and this is the first point of contact of constituents in the chyme as it is being processed. Authors of one study described this as follows: “Though only a single layer of cells, the intestinal epithelial cells (IECs) are the mainstay of the intestinal barrier and serve as a physical barrier. The IEC lining is continuous, and the contact between IECs is sealed by what are known as tight junctions.” According to researchers of another paper, tight junctions “are responsible for the paracellular trafficking of macromolecules and, therefore, they contribute to the balance between tolerance and immune response to non-self antigens.”

Researchers identified a biochemical (zonulin) that is the only known modulator of intercellular tight junctions (TJ). In other words, zonulin is the biochemical that widens the tight junctions between intestinal cells and it is considered by researchers to be the trigger causing leaky gut.

According to an expert on zonulin, Dr. Alessio Fasano, “Zonulin works like the traffic conductor or the gatekeeper of our body’s tissues. Zonulin opens the spaces between cells allowing some substances to pass through while keeping harmful bacteria and toxins out. It has a major effect on intestinal permeability.”

In his research on individuals with celiac disease (a digestive disorder stemming from an immune reaction to gluten in common grains), those people with a genetic risk of celiac disease were given a gluten challenge. Fasano found a 70% increase in intestinal permeability as well as a significant increase in zonulin in this group. When given an agent to block zonulin, after another gluten challenge, there was no increase in IP.

According to another source, the causes of increased zonulin and leaky gut are parasites, small intestinal bacterial overgrowth (SIBO), foods containing gliadin (a protein in wheat), and candida overgrowth/fungal dysbiosis.

Probiotic “Plugs”

The fix for any leak is a plug. In the case of leaky gut syndrome, because part of it is caused by a probiotic insufficiency or imbalance (dysbiosis), it makes sense that probiotics can, to an extent, be an effective “plug.”

Authors of one review explained, “One of the important cytoprotective effects of probiotics in the intestinal mucosa is to strengthen the epithelial tight junctions and preservation of mucosal barrier function. Probiotics not only enhance barrier function by inducing synthesis and assembly of tight junction proteins, but also preventing disruption of tight junctions by injurious factors.”

One trial looked specifically at the link between zonulin and probiotic intake. This randomized, double-blinded, placebo-controlled trial observed effects of probiotic supplementation on markers of intestinal barrier, oxidation and inflammation, at rest and after intense exercise in 23 healthy, athletic men. The multi-strain probiotic used in the study contained Bifidobacterium bifidum W23, Bifidobacterium lactis W51, Enterococcus faecium W54, Lactobacillus acidophilus W22, Lactobacillus brevis W63, and Lactococcus lactis W58. The volunteers took the probiotic or placebo for 14 weeks, and the results showed that “zonulin decreased with supplementation from values slightly above normal into normal ranges and was significantly lower after 14 weeks with probiotics compared to placebo.”

Probiotics, via protection of the intestinal epithelium, can improve certain conditions. For example, one double-blind, placebo-controlled, crossover study showed that six weeks of daily consumption of the strains Lactobacillus rhamnosus 19070-2 and L reuteri DSM 12246 was able to stabilize intestinal barrier function and decrease gastrointestinal symptoms in subjects with atopic dermatitis (a skin condition).

Other Ways to Close the Gaps

Probiotics, overall and no matter the strain, are beneficial for gut health, promoting normalization of gut function and structure (i.e., barrier). But there are other things you can do to help promote healthier barrier function and reduce intestinal permeability.

Decrease consumption of refined carbs (white rice, breads, pastas). These contribute to daily consumption of sugar, which is an agent that can impair barrier function.

Be very conservative with taking non-steroidal anti-inflammatory medicines (aspirin, naproxen, and ibuprofen). These are known to increase intestinal permeability. Authors of one study declared, “Virtually all studies agree that all conventional NSAIDs increase intestinal permeability in the human within 24 hours of ingestion and that this is equally evident when they are taken long term.”


Research continues to explore intestinal permeability: its causes, its impacts and what it contributes to in human health conditions. By following a lifestyle anchored on healthy habits and taking probiotics, you can help fortify the integrity of your gastrointestinal barrier. And this may keep you in a state of optimal health and wellness for the long term.

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