The Coho Functional Medicine guide to leaky gut & intestinal permeability

Leaky gut lies behind a host of health problems, here's what it is and how to fix it

Digestive health is one of the hottest topics in health right now. And with good reason.

Leaky gut (more properly called increased intestinal permeability) is an essential aspect not only gut health, but of overall health.

In this Coho Functional Medicine guide to leaky gut and intestinal permeability, we’ll take a deeper dive into leaky gut and how it can lie behind your health problems.

Functional Medicine leaky gut blog flyer showing villi and viruses

People are becoming more and more aware of the impact of intestinal health on digestive conditions like Irritable Bowel Syndrome (IBS) and Gastroesophageal Reflux Disease (GERD).

But there’s also a growing awareness of wider affects that poor gut health has on the whole body:

Table of Contents

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Leaky gut: structural integrity

A healthy gut is absolutely central to your overall health.

Having a healthy digestive system means much more than simply being free of annoyances like bloating, gas or heartburn.

A robust, healthy digestive system means being able to:

Maintaining structural integrity – maintaining a healthy intestinal lining that lets the right things through into the blood stream while keeping undesirable things out – is what we’ll be focusing on in this article.

When this structural integrity is compromised, it’s called ‘increased intestinal permeability’ or, more commonly ‘leaky gut’.

If you’ve heard of leaky gut, or think it may be behind any health challenges you’re experiencing, you may be wondering:

By the end of this Coho Health guide to the Functional Medicine approach to leaky gut and intestinal permeability, you’ll have answers to those questions.

What is increased intestinal permeability / leaky gut?

Leaky gut / increased intestinal permeability is where the intestinal barrier that lines the intestinal tract, becomes more permeable – or ‘leaky’ – than it should be.

Specifically, it’s where the tight junctions (that hold the cells of the intestinal lining together) become loose or break completely, and let allergens or pathogens through into the blood stream.

The intestinal barrier is a single layer of cells in the digestive tract that are critical to human health. This barrier has two main regulatory roles:

Our gut lining is exposed to everything we swallow, whether that’s food particles, bacteria, pesticides, dust, chemicals, or dirt.

The intestinal barrier must decide what to do with all these things.

Should it allow them to pass through into the blood stream because they are considered beneficial to our health, like nutrients from our food are?

Or should they be kept in the digestive tract to move on through, leaving the body via the bowel as they are considered unhelpful or potentially harmful.

Essentially, the intestinal barrier plays the role of a gatekeeper, and a special protein called Zonulin is what determines how open or closed these gates, known as tight junctions, should be.

“The intestinal barrier is essential in human health and forms the interface between the outside and the internal environment of the body ”  (1)

When functioning normally, the gut barrier is naturally a little permeable and keeps us healthy by keeping out potentially hazardous materials, while letting nutrients and water in.

But when it starts to become more permeable (or “leaky”) we run into problems.

It might be difficult to imagine, but what is inside our gut isn’t actively inside our body until it passes across this barrier. 

When the intestinal barrier malfunctions, and substances that should be eliminated from the body are instead absorbed into the blood steam, inflammation and immune responses are triggered.

The consequences of this can manifest in many different ways and in many different body systems.

A dysfunctional intestinal barrier can, and does, result in increased inflammation.

The inflammatory immune cells in the blood are then carried to other parts of the body.

When this happens, symptoms of a leaky gut can manifest anywhere in the body

Other barriers also have the potential to be ‘leaky’ – such as the skin barrier, and the blood brain barrier.

Signs and symptoms of leaky gut / increased intestinal permeability

Because in leaky gut the allergens and pathogens enter the blood, and blood travels to every part of the body, the inflammatory and immune system affects can present in a variety of ways:

Digestion – gas, bloating, reflux, food sensitivities, nutrient deficiencies

Skin – rashes, eczema,  acne, rosacea, hives, psoriasis,

Mental – brain fog, headaches, migraines, depression, ADHD

Pain – muscle or joint pain

Energy – fatigue

Allergies – sinusitis, hay fever, frequent infections, sensitivities

However, it’s also possible that you can have a leaky gut without experiencing any obvious symptoms at all, while at the same time, the low grade inflammation resulting from leaky gut could be contributing to longer term chronic health conditions.

Conditions associated with leaky gut / increased intestinal permeability

Increased intestinal permeability has been described in patients with:

 and many other diseases. 

Common causes of leaky gut / increased intestinal permeability

There are many factors that can interfere with the function of the gastrointestinal system and the intestinal barrier, but common factors include:


Diet and nutrition contributes to leaky gut in several ways:

A pro-inflammatory diet containing high refined carbohydrates, processed oils and sugar has the potential to cause a leaky gut  (6)

Gluten-containing grains (wheat, barley, spelt, rye) can be a trigger for a leaky gut.  

Gluten can increase levels of Zonulin, a protein that modulates the intestinal tight junctions.

A high level of Zonulin is more likely to be associated with greater intestinal permeability.

Therefore gluten is often a driver of increased intestinal permeability (7) .

In those with coeliac disease, the potential of developing a leaky gut is greater. 

Dairy can also be a factor in leaky gut.

The protein in milk can damage tight junctions (8) conversely kefir has been shown to be beneficial for a leaky gut (9)

A diet low in nutrients, lacking in diversity and low in fibre can lead to vitamin deficiencies.

Nutrient deficiencies that may be involved in increasing intestinal permeability include Vitamin A, Vitamin D and Zinc (other nutrients are also important for maintaining a healthy gut barrier). (10 – 12)

Seemingly healthy foods, such as lentils, beans and chickpeas may also cause a leaky gut in some individuals.

Lectins are proteins found in legumes and grains, and can potentially be a problem for some people, as they can bind to the cells in the intestinal tract and disrupt the barrier.(13)

It is possible to reduce the impact of lectins, by soaking and boiling legumes correctly.

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An unhealthy gastrointestinal system

If your digestive health is already poor and you have an altered diversity of gut bacteria, it could make you more susceptible to developing a leaky gut, as well as conditions such as Small Intestinal Overgrowth (SIBO), Inflammatory Bowel Disease (IBD) and Irritable Bowel Syndrome (IBS)

Gastrointestinal infections with candida and Helicobacter Pylori, for example, can be associated with a leaky gut.

Candida and H.pylori both have the potential to pass through the intestinal barrier and increase risk of developing a leaky gut (14,15).

Gastrointestinal infections with gram negative bacteria can also cause a leaky gut, and Lipopolysaccharides (LPS) (bacterial toxins) produced by gram negative bacteria, can translocate through the intestinal barrier and travel to joints.

This is seen in patients with rheumatoid arthritis, or in those with inflammatory skin conditions such as acne or psoriasis, where LPS can cause inflammation and damage.


Exposure to mould mycotoxins can affect your gut microbiome, which in turn can lead to a leaky gut. (16)

Mould exposure is common if you’re working in, or living in, a water damaged building or damp environment, and through some foods e.g., coffee, nuts, dried fruits (usually due to the storage methods used, or length of time these items are stored for).


Steroids, painkillers, birth control pills, proton pump inhibitors and antibiotics, especially if taken over a long period of time, are just a few of the medications that can contribute to a leaky gut.

However, with anti-inflammatory medications such as NSAIDs, the intestinal barrier can become more ‘leaky’ within just 24 hours.

If you have to take these medications regularly, then more support may be required to reduce increased intestinal permeability (17).


Whether it’s physical stress, for example:

or mental (e.g. anxiety), stress may increase the potential for a leaky gut. 

Chronic stress also reduces digestive enzymes and HCl, which are required to break down food.

Reduced digestive capacity (caused by high stress) can contribute to increased intestinal permeability, increased food sensitivities and dysbiosis.

Hence keeping stress levels under control is super important for reducing the potential for a leaky gut.

Intense exercise

Regular exercise is beneficial for keeping your gut healthy but there’s a fine balance.

Strenuous exercise can have the opposite effect and potentially increase a leaky gut, so additional care may be required in those who regularly perform strenuous exercises / physical activity.


Poor sleep has been linked to leaky gut due to the resulting dysbiosis and increased Lipopolysaccharides (LPS) (bacterial toxins). (18) 

The conventional medicine approach to leaky gut / increased intestinal permeability

Well, there isn’t a conventional medicine approach to leaky gut / increased intestinal permeability.

Unfortunately, there is no perfect test to diagnose a leaky gut, and it cannot physically be seen in endoscopies or colonoscopies.

Generally speaking, within conventional medicine, increased intestinal permeability is not recognised as a physiological state that can contribute to chronic symptoms or chronic health problems, or is not recognised as a physiological state at all.

In fact, the reason we’re frequently referring to this physiological state as ‘increased intestinal permeability’ as well as ‘leaky gut’, is that ‘increased intestinal permeability’ is the proper medical term for leaky gut.  

If you do speak to a medical professional, and start talking about your leaky gut, we wouldn’t want you to receive an (at best) polite look of ‘here we go again’.

And, let’s be honest, a ‘leaky gut’ doesn’t sound very scientific.

However, regardless of what we call it, increased intestinal permeability is a ‘thing’, has been scientifically researched, and is extremely well documented in the literature. 

Below are the some of the testing options we currently use in a Functional Medicine approach to leaky gut.

Testing options to identify leaky gut / increased intestinal permeability

A comprehensive stool test can specifically test for the Zonulin (the gate keeper) and if Zonulin is high, this can be indicative of a leaky gut.

This test also assesses for gastrointestinal infections and dysbiosis factors that can contribute to a leaky gut.

The below test result is from a comprehensive stool test, and shows high levels of Zonulin:

A Lactose Mannitol Home Test is the gold standard among some conventional medical practitioners.

This test involves drinking a sugar solution of lactose and mannitol (sugars of different molecular weights) and then a urine sample is collected a few hours later.

Levels of the different sugars in the urine are measured and this helps to identify the degree of intestinal permeability. (19)

Mannitol serves as a marker of trans-cellular uptake and lactulose (which should only be very slightly absorbed), serves as a marker for mucosal integrity. 

A high lactulose to mannitol ratio indicates increased intestinal permeability.

The Functional Medicine approach to leaky gut / increased intestinal permeability

Fortunately, there are effective strategies that can be implemented to heal a leaky gut and improve overall health.

By supporting intestinal barrier function and integrity, with targeted nutrients (through foods and supplements), as well as reducing physical and mental stress, it is possible to restore optimal barrier function and improve overall wellbeing.

A Functional ‘5 R’ approach is a step by step strategy which is designed to optimise gastrointestinal health, including optimising intestinal mucosal barrier function.

The 5 R framework can be adapted and tailored to the requirements and circumstances of each individual, based on signs, symptoms and test results.

The ‘5 R’ Approach

The first ‘R’ is Remove

Any factors that may be impairing gastrointestinal function are removed.

This includes food intolerances and sensitivities, as well as any infections such as Helicobacter Pylori, Candida, or bacterial infections such as Klebsiella pneumoniae.

The next ‘R’ is Replace

This step is all about giving the body more of what is required, particularly when thinking about digestive support.

This can mean supporting hydrochloric acid (HCl) levels, pancreatic enzymes, or bile acids. Increased food reactions can be a sign of suboptimal digestion of proteins.  

We then move to the following stages:


In this step we are focusing on replenishing beneficial bacteria in the gut, and helping to improve bacteria diversity in the microbiome.

Pre- and / or pro-biotics, certain fibres and resistant starches, would be considered.


The intestinal lining and mucosa are supported through nutrients such as vitamin A, vitamin D, zinc, collagen, L-glutamine and colostrum, as well as foods such as bone broths.


This step often gets overlooked, as perhaps it is considered to be less important.

But actually, the ‘rebalance’ step is critically important to avoid going round in circles, so we keep the gut happy and healthy long term.

This step is very much about lifestyle interventions to support the gut-brain axis, microbiome diversity, preventative health (thereby reducing the need for medications), spending time outdoors in nature, and implementing regular stress reduction techniques.

Foods that can support the repair of a leaky gut

Food plays a foundational role in the repair of a leaky gut:

Glutamine and collagen are both important, and are found in bone broths and fish stocks

Omega 3 fatty acids like those found in oily fish, algae, seaweeds, flaxseeds and walnuts are also important

Vitamin D, which is predominately obtained from sunlight exposure, but a small amount in mushrooms and eggs

Vitamin A is found in organ meats, and red and yellow coloured vegetables

Quercetin, found in apples, onion and garlic.

Zinc found in pumpkin seeds and shellfish like oysters

When diet alone isn’t able to meet your nutritional requirements, then high quality nutritional supplements can be helpful. 

Other supplemental support, such as colostrum, immunoglobulins and butyrate also support the gut lining and the microbiome.

How long does it take to heal a leaky gut?

The length of time required to repair a leaky gut can depend on the underlying conditions and potentially, on how long the intestinal barrier has been dysfunctional for. 

It could, for example, take anywhere between 4 weeks to 6 months (in more complex cases).

For most people, we’d say around 2-3 months.

Can fixing your intestinal permeability arrest progression of autoimmune disease?

The short answer is: yes.

The human body is phenomenal.

It can tolerate many exposures to toxic chemicals, heavy metals, stress, and foods that irritate the gastrointestinal system, before the development of a dysfunctional intestinal mucosal barrier – leaky gut.

We know that many people with autoimmune disease have increased intestinal permeability.

But what we don’t know yet, is whether the increased intestinal permeability causes the autoimmunity, or whether the autoimmunity causes the increased intestinal permeability (or perhaps it is both).

As we mentioned earlier, if we have increased intestinal permeability, then this can go on to affect our immune system and our microbiome (20).

And it’s not only the ‘bad’ bacteria in our intestinal system that can be problematic.  

If there is a ‘leaky gut’, then even the commensal (‘good’) bacteria can escape the intestinal lumen and cause inflammation.

The resulting ‘leaky gut’ then acts as the gateway to inflammation, and this can cause further immune system dysregulation.

And that immune system dysfunction can lead directly autoimmune conditions:

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The wrap...

Leaky gut is a factor that lies behind a huge range of health problems. 

When it comes to leaky gut, prevention is better than cure, and the best option is to never get a leaky gut.

You can do this by pro-actively taking care of your intestinal system, avoiding the main factors that drive increased intestinal permeability.

The second best option is to heal your leaky gut as soon as you can, and ideally well before the resulting inflammation and immune system dysfunction turns into a health problem.

Here’s a quick summary of some of what we’ve covered in our article today:

1/ Practically speaking, the contents of our digestive tract remain outside of the body – it’s only when those contents cross the intestinal barrier that they are truly inside the body

2/ Your intestinal barrier should be permeable, so it lets digested nutrients into the body, but just not TOO permeable, so it lets allergens and pathogens into the body

3/ Lifestyle factors like stress, as well as what we eat and drink, can make our gut ‘leaky’

4/ Leaky gut can be healed but we need to determine why it is leaky first, otherwise you can go around in circles for years (which is what many people do)

5/ Leaky Gut is linked to autoimmune disease and many other chronic diseases

If you think the Coho Functional Medicine approach to leaky gut can help you, you can book a free 15 minute discovery call with us here.

We offer Functional Medicine consultations in the UK, in Mallorca, and to clients around the World through our virtual Functional Medicine clinic.

To your optimised, healthy future,

Lulu & the Coho Health team

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