Digestive tract showing the stomach and intestines

Leaky Gut, Autoimmunity, And Mental Health. What’s are the link? Part 2


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For part 1 of this post series, check out it here.

Leaky gut, allergies, and autoimmunity

 Allergies and autoimmunity are directly linked to our immune system. They result when our immune system works a bit too hard – when our immune cells become a little too active.


Allergies occur when our immune system is activated to fight things that are not harmful, like certain foods/food proteins (antigens), 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 (perceived threat).


Autoimmunity, on the other hand, is when our immune system is activated to fight our own cells and tissues. The immune system becomes “intolerant to self.” For example, type 1 diabetes (an autoimmune disease) occurs when our immune system fights the insulin-producing (beta) cells in our pancreas. After continued inflammation, enough of these cells die and we eventually need to start monitoring our own blood sugar levels and provide our bodies 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 play a bigger role than we once thought. This is because of the impact that happens when undigested food (proteins or antigens), bacteria, viruses, endotoxin etc. enter our bodies and how that stimulates/triggers our immune system to fight them. A large part, about 70%, of our immune system is located in the gut, just on the other side of that one-cell thick layer of enterocytes (a.k.a. the cells that line the length of the intestinal/digestive tract).


When our bodies detect things in our circulation that don’t belong there (like undigested food or bacteria) our immune system kicks in. This immune response to things that have “leaked” in causes the release of even more inflammatory compounds. So while the initial allergic response and inflammation/irritation  happens in the gut, these inflammatory compounds are absorbed into the bloodstream where they can affect other parts of the body too.


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 our bodies and our immune system’s response to them.


Having a healthy gut microbiota plays an important role in how our immune systems mature from when we were infants. Dysbiosis (bacterial imbalance) in our gut at an early age can promote undesirable changes in our immune response, and increase the risk of allergic and autoimmune diseases. In this sense, early gut health and the health of our gut bacteria set us up for future health.


It seems that gut dysbiosis and “leaky gut” might be part of the chain of reactions that lead our immune cells to start attacking things they really don’t need to such as various tissues and organs throughout the body.


Leaky gut and mental health

 Stress and mental health issues are associated with inflammatory bowel diseases and leaky gut as well.


Stress and stress hormones can impact mood-related neurotransmitter function in the brain and, in turn, increase the risk of developing gut disorders, or aggravating existing gut disorders; something referred to as the gut-brain-axis. Several studies have found that patients with inflammatory gut conditions experienced worsening symptoms after stressful events. Chronic, or long-term, stress and depression is associated with more gut pain, leaky gut, and other inflammatory gut conditions like Crohn’s and ulcerative colitis. Stress can affect changes in the microbiota and the lining of the gut, and can further increase the gut inflammation. Both animal and human studies show that being under stress increases their intestinal permeability and inflammation.


We used to think that the brain sent instructions down, in one direction, to control all parts of our bodies. We’re learning that a lot of the communication between the gut and the brain starts in the gut and goes up to the brain. Several studies show that in about half of people studied, gut symptoms arose before the mood issues did.


People who have gut disorders have a higher risk of developing anxiety or depression. Sometimes experiencing symptoms like abdominal pain, bloating, and discomfort can affect the quality of life and moods of people who have inflammatory bowel disease.


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These links between the gut and mental health are because of the “microbiota-gut-brain axis.” This axis, or highway, includes many connections between the two of them, including nerves, hormones and neurotransmitters.


When the areas of the brain associated with stress are activated, this initiates the stress response. The stress response is twofold. First, it includes the release of stress hormones (hypothalamic-pituitary-adrenal axis – HPA axis) that go through the whole body. Second, it includes activation of the “fight or flight” (autonomic) part of the body’s nervous system. Both the hormones and autonomic nervous system affect the gut. And these can affect all three layers of the gut lining.


One of the key stress hormones of this HPA-axis is from the adrenal glands (the “A” in HPA). It’s the infamous stress hormone called cortisol. Cortisol is released into the bloodstream when we’re under stress. Cortisol directly affects the gut by reducing our ability to properly digest food, and instead prioritizes survival. It essentially prepares for “fight or flight” by slowing down the “rest and digest” functions.


FUN FACT: Mouse studies show that short chain fatty acids (SCFAs) may help to normalize the leakiness in not just our gut lining, but our “brain lining” (e.g. “blood-brain barrier”) too. This is why fermentable fibers (prebiotics) are important for overall health; as the gut bacteria ferment the fiber (eat them essentially), they produce a type of fat (SCFAs) which the cells of the digestive tract use for energy but that also influence how the gut bacteria work and how they, in turn, prevent a leaky gut and leaky brain.


What you can do about leaky gut

When our “good” gut microbes are happily eating their favourite foods they have positive effects on our gut – crowding out the “bad” microbes and producing beneficial anti-inflammatory compounds like SCFAs.


FUN FACT: The type of microbes that live in your gut is established by the time you’re 3-5 years old. About 30-40% of them can be influenced in later life by things such as diet.


According to Aguayo-Patron, 2017:


“Diet is the main factor that influences gut microbiota composition.”


Things to consider when it comes to promoting a health gut:

1] Eat more fresh, unprocessed and minimally processed foods

We’re talking things like:

  • Fruits and vegetables
  • Nuts and seeds
  • Fish
  • Legumes


This is sometimes referred to as an “old fashioned” diet. It includes fresh and minimally processed foods that are closer to the way they’re found in nature. These promote a healthy mix of the “good” gut microbes.


One of the reasons is because these foods contain higher amounts of fibre and “resistant” starch. Sugars and easily-digested starches are broken down and absorbed into the bloodstream as sugar. Resistant starches and fibre, on the other hand, are “resistant” to this process and make it all the way through our intestines to where most of our gut microbes live. These can then become food for our “good” gut microbes and promote their health.


Another possible reason why fresh and unprocessed foods are beneficial is that some of the additives used in ultra-processed foods can also affect our gut microbiota. This leads us to the second thing you can do about leaky gut.


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2] Ditch the ultra-processed and fast foods!

These are the quick and easy foods that are:

  • Ready to eat
  • Ready to heat
  • Pre-packaged
  • Convenient
  • Fast


They tend to be high in calories, processed fat, added sugar, salt, and contain additives/artificial colours. These are the foods that have a lot of sugar and easily digested starches and not a lot of fiber and resistant starches.


These types of foods also promote inflammation and gut dysbiosis – factors associated with leaky guts!


People who tend to eat less of these, and more fresh and unprocessed foods tend to have happier gut microbiota, less inflammation, and a nice strong non-leaky gut lining.


3] Pay attention to potential food intolerances & sensitivities

Some gut symptoms may be related to food intolerances. Certain people may have undiagnosed celiac disease, or be sensitive to gluten and can benefit from removing it from the diet. There are a lot of gluten-free foods available now, however ultra-processed gluten-free foods are still ultra-processed and should be avoided in favour for fresh and unprocessed foods.


Also, some people are intolerant to certain carbohydrates called FODMAPS (fermentable oligo-, di-, and mono-saccharides and polyols). These are found in stone fruits, legumes, lactose-containing foods, and artificial sweeteners.


Ask your health professional to see if you should be tested for food intolerances.


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4] Reduce alcohol

Alcohol can stress our friendly gut microbes and can disrupt the function of our three-layered gut lining. It can cause bacterial overgrowth, and at the same time reduce some of the friendly “good” microbes like Lactobacillus.


FUN FACT: Some “bad” bacteria, including E. coli can produce alcohol, so this may be one of the ways that they contribute to leaky gut.



5] Consider probiotics

Probiotics are live microorganisms that have a beneficial effect on human health. They are found in fermented foods like yogurt, kefir, kombucha, miso, kimchi, and fermented vegetables. They are also available as dietary supplements.


Infections and use of antibiotics, especially during the first months of life, can have a negative effect on our gut microbiota. If you have to take an antibiotic, ask your healthcare professional if you should also take certain probiotics to help reduce the impact on your gut microbiota.


Clinical trials are being done to test whether probiotics may benefit inflammatory gut conditions even without antibiotic use. More research is needed to confirm which amounts of which types of probiotics are the most beneficial for which conditions.


CAUTION: Before taking any supplements, make sure to read the label and heed the warnings. If you are taking other supplements or medications or if you have a medical condition, be sure to consult with a knowledgeable healthcare professional first.


Bottom line

Leaky gut, or “intestinal permeability” is linked with many conditions of the gut, the body, and the mind. While research is still figuring out exactly how this happens and what comes first, there are definitely steps you can take today to help optimize your health.


Eat more whole, unprocessed foods, and ditch ultra-processed foods. Reduce alcohol consumption and consider probiotics. And, if you think you may have a food intolerance, be sure to speak with your healthcare professional.


Doug Cook RDN is a Toronto based integrative and functional nutritionist and dietitian with a focus on digestive, gut, and mental health.  Follow me on Facebook, Instagram and Twitter.