Leaky Gut: Understanding Intestinal Permeability and the Connection to Disease

Leaky Gut: Understanding Intestinal Permeability and the Connection to Disease

  • Gut Health

  • By Mathieu Millette, Ph. D., Mcb. A.

    Many lifestyle factors like chronic stress, poor dietary choices (such as highly processed foods), smoking, and the over-prescription of antibiotics all contribute to the general malaise that plagues so many of us. But these factors also contribute to a much more specific malady that is becoming more common (and better understood) in today's world: intestinal permeability (aka “leaky gut syndrome”).

    As we understand more about the gut, we can start to make connections about the role a leaky gut plays in disease etiology, due to the constant onslaught of unwelcomed inflammatory toxins entering and circulating the bloodstream. In fact, increased intestinal permeability has been correlated with several health issues including eczema, acne, hormonal imbalance, food sensitivities to more critical illness such as inflammatory bowel diseases, celiac disease, food allergy, irritable bowel syndrome, and – more recently recognized – obesity and metabolic diseases.1

    As microbiome experts, knowing that leaky gut or bowel leakage leads to disease is not enough - we want to make sure you understand how the gastrointestinal tract operates so you have a better understanding of what is happening in your body to make informed choices about who to nourish and support it.


    The Anatomy of the Gut

    In the most basic sense, our gastrointestinal system (GI tract) is a long tube of organs that begins at the mouth and runs all the way to the anus. Each organ and area of the GI tract plays an important and different role in the digestive process, while collectively working together to perform the essential function of breaking down food into absorbable nutrients, which in turn provide the body with energy.2

    This tube-like structure of our digestive system creates a protective wall, ideally letting only the things our body needs in and things that may harm us, out, while also preventing the loss of water and electrolytes. Known as the intestinal barrier, it covers approximately 400mand requires about 40% of the body’s energy expenditure.1

    The human gastrointestinal tract contains four layers. The innermost layer, the mucosa, itself includes three sublayers: the epithelium (which includes glandular tissue), lamina propria (which contains vascular support for the epithelium as well as mucous glands) and muscular mucosa (a thin layer of smooth muscle that allows for the movement of the mucosa).

    You may be thinking that diving into such level of detail around the gut is unnecessary, but it is vital for understanding what exactly is happening when it comes to intestinal permeability.

    The mucosa layer of the gut has evolved to facilitate two very specific functions in our body: to allow the peaceful co-existence with the bacteria that call us home (versus creating chronic inflammation) and to provide a controlled and specific amount of inflammation as a defence response when there is an attack from an invader (say a pathogen or toxin). When working in harmony, the layers of our mucosa can act as both a physical and immunological barrier to keep us healthy.1


    Understanding Intestinal Permeability

    Intestinal permeability is a functional feature of the intestinal barrier, occurring at given sites along the gastrointestinal tract. Not all intestinal permeability is bad. Normal intestinal permeability happens in healthy individuals and the flux of molecules across the intestinal barrier occur without any inflammation or consequence to intestinal function. When there is impaired intestinal permeability, however, becomes chronically altered (compared to normal permeability) leading to a loss of homeostasis, functional impairments and disease.1


    A Compromised Gut Barrier

    The cells of the epithelium, otherwise known as enterocytes, form the primary physical barrier between the lumen (aka the hollow tube portion of your digestive tract) and the subsequent layers. The separation they create is essential as there are a wide variety of environmental agents that can irritate or cause inflammation if they are able to cross.

    In a healthy gut, the barrier function is tightly regulated and requires cooperation from many players including our gut microbiota, nervous system, resident immune cells, and intestinal cells. All the cells are bound together with proteins called ‘tight junctions.’3 These tight junctions are what allows everything that comes into your body to be processed properly without ‘leaking’ into the deeper layers of your gastrointestinal tract and disrupting the proper immune response.

    When these ‘tight junctions’ become compromised (through irritation and inflammation), they loosen, and undigested proteins, toxins, pathogens, and antigens can slide between the epithelial cells, enter our bloodstream and cause our immune system to react.4

    Many factors can alter intestinal permeability and cause leaky gut syndrome, and it can happen both suddenly, after trauma or illness, or over time, otherwise known as chronic inflammatory disease. From a lifestyle and dietary perspective, alcohol, smoking, poor sleep and processed foods can all increase intestinal permeability. And within our body, a disrupted microbiota is a factor not to be overlooked.


    Where our Gut Microbiome fits into it all

    Covering the epithelial cells is a thin layer of mucus, and its integrity is critical to our health as it holds the immune cells necessary to kill off pathogens and protects our epithelial cells from inflammatory causing compounds and bacteria.5

    Therefore, while the microbiota lining our GI tract do not act specifically as the intestinal barrier, they are a vital player in helping to control its ability to function properly and are a central regulator of the epithelial cell functionality.

    When this relationship breaks down (e.g. when there is gut dysbiosis), it can be detrimental to both intestinal and systemic health. To date, several diseases have been linked to changes in microbiota populations or diversity, including atopic diseases, inflammatory bowel disease, diabetes, obesity, cancer and certain neuropathologies.1


    As we learn more about the complex relationship of our intestinal barrier and intestinal permeability, it is only natural to look for ways we can best support its proper functioning or help restore it. The effect of diet on intestinal permeability will be highly individual as genetics will play a huge role, however employing a healthy leaky gut diet (based on whole foods), consuming an adequate amount of prebiotic fiber and supporting microbiota communities with a clinically proven probiotic such as Bio-K+ will go a long way.


    Do you have any other questions concerning the health of your gut microbiome? Let us know in the comments below! Join our community for more healthy tips. Click here to find a store near you. Contact us or follow us on Facebook and Instagram.




    1. Intestinal permeability – a new target for disease prevention and therapy - PMC (nih.gov)

    2. Rolfes, S. R., Pinna, K., & Whitney, E. N. (2012). Understanding normal and clinical nutrition. 9th ed. Belmont, CA: Wadsworth, Cengage Learning.

    3. Microbiota-host interactions in irritable bowel syndrome: Epithelial barrier, immune regulation and brain-gut interactions - PMC (nih.gov)

    4. https://onlinelibrary.wiley.com/doi/full/10.1111/apt.12950

    5. A dietary fiber-deprived gut microbiota degrades the colonic mucus barrier and enhances pathogen susceptibility - PMC (nih.gov)

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    Mathieu Millette Mcb. A.
    About the author
    Graduated with honors from INRS-Armand-Frappier Institute, Dr Mathieu Millette is an authority on probiotics for the last 20 years.
    View all articles by Mathieu Millette
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