I remember the first time I heard the term leaky gut. It was the summer of 2011 while I was reading Tim Ferris’s book, “The 4 Hour Body.” When he mentioned the term, I remember thinking how odd it was. I wondered if the gut could truly be leaky and how on earth that could happen?

Turns out, it is an actual thing! The gut can really be leakier than normal due to unwanted gaps that cause a whole host of problems. This article is part one of a two-part series. I hope you enjoy reading along and learn a new thing or two about leaky gut.

What is Leaky Gut?

Leaky gut, also known as increased intestinal permeability or intestinal hyperpermeability, is one of those terms making the rounds recently. If you’ve been wondering what on earth leaky gut is, how to tell if you have leaky gut, and how to start healing if you have it, then this article will shed some light on this issue for you.

The gut, also rightly known in some circles as the second brain, is not just a tube that absorbs nutrients and gets rid of waste – it’s a complex system that’s a huge foundation of good health. And I’m not just talking about gut health, but the overall health of your body and mind. Your gut helps you break down foods, absorb vital nutrients, and create and expel waste. We know how important it is to get all of our essential nutrients from food – and this is a big part of what your digestive tract does. But there’s way more to the story than just that.

When the gut is not working properly, symptoms can appear. Yes, typical gut and abdominal symptoms, but also other seemingly unrelated symptoms. Did you know that things like allergies, autoimmune diseases, mental health, and stress have all been linked with gut problems? You know when you get a gut feeling about something or when you’re nervous and or excited and you get butterflies in your tummy? That’s your gut communicating with you.

Let’s look at one gut problem in particular – leaky gut. This literally involves tiny “leaks” in your gut lining that can allow more than just needed nutrients and water into your body. To absorb nutrients from your gut into your body, you do need your gut to be a little leaky, otherwise, those much-needed nutrients won’t be absorbed. Unfortunately in certain situations, those gaps can get bigger and remain permanently open causing detrimental health problems.

Researchers are looking into this and I want to share the latest results with you, as well as give you some helpful strategies to optimize your gut health. This, in turn, enhances your overall health.

What Conditions Are Linked to Leaky Gut?

The gut is part of the digestive system, mainly the intestines, which are located in the abdomen. It’s an alive and very complex “tube” from the mouth to the anus teeming with tens of trillions of microorganisms. Your gut acts as a gateway. It decides what’s safe enough to enter the internal circulation of your body to be used to make you healthy and what is deemed foreign or toxic therefore must not be absorbed.

Some of the responsibilities of your gut include:

  • Digest and absorb nutrients and water
  • Prevent toxins and “bad” microbes like bacteria, viruses, or yeasts from being absorbed
  • Shuttles all waste to the large intestine to be eliminated

You may think that symptoms of a leaky gut are only felt in the gut, and you may be right…to a certain extent. Would you be surprised to know that many other symptoms and conditions are associated with leaky gut?

Leaky gut has been associated with:

  • Autoimmune diseases such as Type I diabetes and celiac disease. There’s actually a school of thought that says autoimmune diseases can only happen in the presence of leaky gut!
  • Inflammatory Bowel Diseases such as ulcerative colitis and Crohn’s disease.
  • Psychological stress and mental health
  • And more!

Researchers are still figuring out the exact role that leaky gut plays in these conditions. All in all, there’s no denying connections are present and luckily for you, there are things you can do to improve your gut health. But first, how is your gut structured and what can cause it to leak?

The Three Layers of the Gastrointestinal Tract

The gut has a three-layer lining which allows things you need in and works to keep harmful things out. 

The First Layer of Gut Lining

The first and outermost layer of your gut lining is just one-cell thick. It acts as a barrier that absorbs the nutrients and water you need while preventing undigested compounds, toxins, and bacteria from getting in. Laid out flat, this layer has a large surface area that’s comparable to the size of half a badminton court! It’s pretty amazing to think we’ve all got something that size squished up inside us!

This layer also has at least seven different types of cells with 90% being a type of cell called enterocytes. These enterocytes actively absorb what you need while keeping out what you don’t. In addition, they also help to create and regulate the other two layers.

FACT: Most enterocytes are replaced with new ones every 3-5 days or so.

Enterocytes are held together with different types of bonds. The one most studied is called a “tight junction.” These tight junctions are made up of several types of protein. When they loosen, it creates tiny holes or gaps in this first layer since the cells are not “stuck” together as much as they should be.

The Second Layer of Gut Lining

The second layer is made up of mucus. This mucus layer provides a physical separation between the outermost enterocyte layer and the microbes and food that are inside the centre, or lumen, of the gut. It also contains special proteins that help fight against invaders. This mucus and its special compounds are produced by the enterocytes.

We want the mucus layer to be nice and thick to provide a better barrier between the one-cell layer of enterocytes and protect them from “bad” bacteria that can get in there.

FACT: Animal studies show that mice fed a diet low in fibre have thinner mucus barriers.

The Third Layer of Gut Lining

The third and innermost layer inside your gut lining is where your friendly resident gut microbes live. Your guts contain billions of microbes – over 1 kg worth. These microbes include bacteria as well as other types of friendly microbes.

This layer of gut microbiota has two major functions to help promote a healthy gut lining:

  • They crowd out “bad” bacteria by taking up space and eating the “good” food (i.e. fibre and resistant starch, which we’ll get into in a bit).
  • They help to regulate the digestion and absorption of nutrients to nourish the first-layer enterocytes. One of the types of beneficial compounds they produce
  • is called “short-chain fatty acids” (SCFAs). These are considered to be anti-inflammatory and are also used as fuel for the enterocytes.

When the three layers aren’t working optimally, the tight junctions loosen, and leaks occur. This allows unwanted things to enter into the body’s circulation. In conclusion, this is how your gut health affects your overall health.

Leaky Gut and Your Gut Bacteria

Hundreds of friendly gut microbes reside in the third, innermost layer of your gut. One of the main types of bacteria in your gut is Firmicutes (e.g. Lactobacillus) which are very good at helping extract calories from foods. Then there’s Bacteroidetes, which aren’t as efficient at this job.

FACT: You actually have more bacteria cells in and on your body than you do human cells.

It appears that your gut microbes might actually begin the whole process of leaky gut. According to Sturgeon and Fasano, 2016:

“It is now clear there is a symbiotic relationship between the microbiome and the host. As early as 2001, it was described that commensal bacteria have an effect on intestinal permeability.”

Here’s how we think this happens, based on the current research:

  • The third innermost layer of the gut lining, the microbiota, get out of balance for one reason or another such as overuse of antibiotics, types of food and fibre that you consume, etc.
  • Inflammatory molecules (including zonulin which controls the tight junctions) are released and fewer anti-inflammatory ones like short-chain fatty acids SCFAs (these are by-products of fermented dietary fibres by beneficial bacteria in the colon) are available.
  • This inflammation disturbs the tight junctions in the first layer of enterocytes, hence creating tiny leaks that allow the passage of harmful compounds into your body.

It starts when the gut microbiota are in dysbiosis, meaning an imbalance of “good” and “bad” microbes. This promotes an inflammatory response because some of the “bad” microbes are pushing out the “good” ones that produce the anti-inflammatory short-chain fatty acids. SCFAs are anti-inflammatory and are also used as fuel by the enterocytes. Some of these SCFAs promote the production of the mucus layer (the second layer) and even help to improve the tight junctions in the enterocytes in the first layer. These beneficial gut microbes produce the SCFAs when they ferment the fibre and resistant starch you consume.

FACT: One study looked at children who were at risk of developing type 1 diabetes (which is an autoimmune condition). Researchers found that those children who had an increase in one of the “bad” microbes went on to develop autoimmunity months later which led to type 1 diabetes.

Another possibility that researchers are looking at is that some of these “bad” bacteria produce a toxin that mimics zonulin. Zonulin is a protein naturally released by your enterocytes when they’re exposed to certain things you eat, such as “bad” bacteria on your food and gliadin (part of the gluten protein found in wheat and other grains). Blood levels of zonulin tend to be higher in people with autoimmune conditions like celiac disease and type 1 diabetes. All of these toxins cause increased inflammation which then irritates the gut, resulting in loosening of those tight junctions.

Based on the research so far, this is the way we think we develop leaky guts. But, how does this relate to autoimmunity?

Can Leaky Gut Cause Allergies and Autoimmunity?

Allergies and autoimmunity are directly linked to your immune system. These conditions occur when your immune system works a bit too hard making your immune cells become a little too active. This makes even more sense when you realize that about 80% of your immune system is located in the gut. 

Allergies occur when your immune system is activated to fight things that are not harmful, like certain foods, pollen, or pet dander. The body thinks they’re dangerous invaders that must be fought and sends out immune cells that cause inflammation to try and eliminate the allergen.

Autoimmunity, on the other hand, is when your immune system is activated to fight your own cells and tissues. The immune system becomes “intolerant to self.” For example, type 1 diabetes (an autoimmune disease) occurs when your immune system fights the insulin-producing cells in your pancreas. After continued inflammation, enough of these cells die that you eventually need to start monitoring your own blood sugar levels and provide your body with external insulin. This occurs more often in people who have type 1 diabetes in their families.

Many things can contribute to autoimmunity and leaky gut may be a bigger factor than we once thought. This is because of the impact of partially digested or undigested food or bacteria entering your body and triggering the immune system. Then in turn, how your immune system tries to fight these invaders. A large part of your immune system (about 80% as mentioned above) is located just on the other side of that one-cell thick layer of enterocytes.

When your body detects things in your internal circulation that don’t belong (like undigested food or bacteria), your immune system kicks in in a bid to protect you. This immune response to things that “leaked” into your body can cause the release of even more inflammatory compounds through the gaps or leaky gut into your body and bloodstream (i.e. on the other side of the first layer of enterocytes). 

The allergic and inflammatory responses that happen around your gut may affect the gut directly. However, once these foreign particles are absorbed into the bloodstream, they can affect other parts of the body too. These may include areas where you may have weak links or susceptibility to certain diseases or conditions, especially when it runs in the family.

This is the connection we see between leaky gut, allergies, and autoimmunity. It’s not just the leaky gut, it’s the interactions between what leaks into your body and your immune system’s response to them.

Having a healthy gut microbiome plays an important role in how your immune system matures as you get older. Dysbiosis in your gut at an early age can promote changes in your immune response, and increase the risk of allergic and autoimmune diseases. It seems that gut dysbiosis and “leaky gut” might be part of the chain of reactions that lead immune cells to start attacking things they really don’t need to.

How Does Stress Affect Your Gut Health?

At this point, I’m sure you all need a break, so here’s a good place to stop for now. We’ve covered a lot of material and I’d like you to have time to digest it before you dig into part two of this important two-part series on leaky gut. 

When you’re ready, you can catch part two here, which focuses on stress and how it affects the health of your gut. I’ll also provide you with actionable tips to get your gut in tip-top shape.



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