Can Leaky Gut Cause Leaky Brain?

leaky gut, actin, autoimmunity

Do you possibly have leaky gut or leaky brain syndrome? Can one lead to the other? 

The symptoms of either leaky gut or leaky brain are somewhat hard to pinpoint but include digestive symptoms (diarrhea, gas, bloating, indigestion), food insensitivities, fatigue and things like difficulty concentrating, headaches / migraines, memory loss or other cognitive issues. 

If you suffer from these types of symptoms then read on for details about leaky gut and brain syndromes and how we can help.  

In this blog on leaky gut and leaky brain, you will learn:

  • About the gut, the brain and how the two are interconnected
  • How a leaky gut can cause a leaky brain 
  • What are the consequences for your long-term health

We have already written separately about leaky gut syndrome here and leaky brain syndrome here. In an upcoming blog, we will address how to resolve leaky gut and leaky brain so keep following us!

But first, let’s re-cap:

The Gut 

The gut is our digestive system. You may also hear it called the digestive tract, the gastrointestinal or GI tract. The gut extends from the mouth, through the esophagus, stomach, small intestine, pancreas, liver, gallbladder, colon and finally rectum or anus. 

What is the Gut Microbiome?

The gut contains a microbiome. The microbiome is the collection of trillions of microorganisms (bacteria, fungi and viruses) that live in the gastrointestinal tract. 

There are a small number of core microbial species shared by most people. Beyond that, populations of microbes can differ quite a lot from person to person. Within one person, the microbial populations stay fairly constant over time. Changes can happen as a result of any changes in a person’s diet, lifestyle or age.  

The microbiome is extremely important for health and well-being. It influences metabolism, nutrition, physiology and immune function. In fact, 70-80% of immune cells reside in the gut. This means that the health of the immune system depends on the health of the gut.

Even in healthy people, the microbiome has both beneficial and pathogenic gut bacteria. In a balanced gut microbiome, the beneficial bacteria outweigh and keep the harmful bacteria under control. If the harmful pathogenic bacteria become too plentiful, then a condition called dysbiosis results. 

Imbalances in the gut microbiome is linked to gastrointestinal (GI) conditions such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), dysbiosis, gut infections and many others. The microbiome influences health more widely and plays a role in diseases like obesity, type 2 diabetes, mental health issues, allergies, autoimmunity, MS, neurological diseases, skin issues and more.

What is Leaky Gut?

Leaky gut is also known as intestinal permeability. It is a condition in which the gut lining becomes permeable or ‘leaky’. The gut lining is meant to be protective and non-permeable. This means that nothing extra should pass through, either from the gut into the body or vice versa. 

Tight junctions are proteins in the gut lining. They are tiny openings that allow nutrients and water to pass through into circulation in the body. They prevent harmful or toxic substances from entering the bloodstream. In the case of leaky gut, the tight junctions have loosened, allowing substances that should not pass through the gut lining to do so. This is permeability of the gut. 

Once tight junctions are loose and the gut is permeable, it literally means that there are leaks in the gut lining. Damaging things can leak through like toxins, bacteria and molecules of partially digested food.  These things are meant to stay in the gut to be metabolized or else eliminated through stool. If they get into the bloodstream, they can cause problems by triggering inflammation. 

As inflammation spikes within the gut, it disrupts the gut bacteria and negatively shifts the health of the microbiome. This creates a vicious cycle that worsens leaky gut, which further affects the microbiome.

Once the gut is permeable, unwanted substances can frequently pass though the gut lining and trigger frequent immune system reactions. This can cause widespread inflammation and an over-reaction of the immune system. This inflammation and over-active immune system can become chronic if the leaky gut is not healed.

The Brain

The brain is the most complex part of the human body. It controls intelligence, behavior, thought, memory, emotion, touch, motor skills, vision, breathing, temperature, hunger and every process that regulates the body. 

  • The brain weighs about 3 pounds in the average adult (Mou Y, 2022). 
  • It is made up of about 60% fat. The remaining 40% is a combination of water, protein, carbohydrates and salts (Mou Y, 2022). 

The Blood Brain Barrier

Because the brain is so critical for life, it is protected by a barrier called the Blood Brain Barrier (BBB). This is a single layer of cells joined together by tight junctions, very similar to the gut lining we have along the digestive tract.  

The role of the BBB is to keep most substances from the bloodstream out of the brain and allow only very few substances into the brain. This is to protect the brain from potentially harmful substances in the bloodstream. Toxins like heavy metals, pesticides, PCBs, other chemicals and damaging proteins can be present in the bloodstream. They are kept out of the brain by the BBB.

The BBB lets substances needed by the brain in, such as oxygen, hormones and nutrients.

What is Leaky Brain?

The BBB is meant to be impermeable to protect the brain. It is there to prevent toxins and unwanted molecules from entering the brain, where they may cause harm. But this lining can become leaky and allow harmful things into the brain and cause health issues. Like with leaky gut, where the tight junctions of the lining can gut lining loosen, tight junctions of the BBB can also become loose. This makes the brain permeable or leaky and is no longer protective. 

When the tight junctions of the brain loosen, we call this blood brain barrier dysfunction, or simply, leaky brain. It is important that a case of leaky brain is identified and resolved. This is critical to protect brain health and cognition over the long term.

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The Gut – Brain Axis: Are they Connected Somehow?

The gut and brain are physically connected via the vagus nerve. The vagus nerve is part of the parasympathetic nervous system and connects the brain and the gut. The parasympathetic nervous system controls ‘rest and digest’ functions such as digestion, heart rate and immune system. 

Gut flora or bacteria control the signaling and communication that take place between the gut and the brain. This is the chemical connection between the gut and brain that send chemical messages back and forth. These chemical messages are conducted via neurotransmitters and hormones, like serotonin and others, and are important for mental health. 

Studies show a strong role of the gut microbiota in brain inflammation/ degeneration and brain aging (Mou Y, 2022). Dysregulation of the gut contributes to systemic inflammation. Pathogenic gut issues, repeated dietary irritants and unhealthy lifestyles all cause inflammation.  

In lab experiments, when there is chronic inflammation due to gut microbiome issues, pro-inflammatory molecules and zonulin can damage both the gut lining and the BBB. They loosen the tight junctions, making the gut and the BBB leaky (Mou Y, 2022). 

Lipopolysaccharides (LPS) are inflammatory toxins made by certain pathogenic gut bacteria. They can cause inflammation if the gut is leaky and pass from the gut into the bloodstream. A compromised BBB allows these inflammatory molecules through the BBB, which results in abnormal emotional activity and temporary memory deficiency (Mou Y, 2022).

Gut issues, bad bacteria producing high LPS and other gut pathogens, antibiotics, stress, microbes and toxins can all lead to inflammation, which may become chronic. Inflammation is a large part of BBB leakiness and chronic disease. Inflammation triggers the immune response. If the immune system is switched on for too long, it can lead to inflammation and eventually to brain disorders. 

Can Leaky Gut Cause Leaky Brain?

Through the gut-brain axis, the gut bacteria have a significant impact on brain health. The tight junctions of the BBB are like those of the intestinal barrier. They are vulnerable to similar things that can increase permeability. This is the mechanism behind leaky gut / leaky brain syndrome (Obrenovich, 2018).

Permeability can increase via inflammatory processes and direct bacterial involvement. Bacteria and LPS from bacteria are highly inflammatory and the BBB is sensitive to the effects of inflammation (Obrenovich, 2018). 

Once the gut is leaky, pathogens can make leaky and penetrate the blood brain barrier to reach brain compartments (Obrenovich, 2018). These small bacterial components, or toxins, can contribute to disease or worsen health without causing obvious illness or infection (Obrenovich, 2018). 

Metabolic Cross Talk and the Gut – Brain Axis

Due to the concept of metabolic cross talk, the gut and brain talk to each other through bacteria, hormones and other signaling substances. This communication between gut and brain is happening constantly. Any negative microbiome issues will communicate with and travel to the brain via the gut – brain axis cross talk. Other pathogens, like environmental toxins, viruses and fungi, communicate or cross-talk as well, causing inflammation and other potential issues (Obrenovich, 2018).

This connection between the gut and the brain means that gut infections and poor gut health have negative consequences for brain health and long-term cognition. This is why it is vital to heal gut infections and issues, as well as any brain health issues. You will learn how to address these problems in our next blog on treating leaky gut / brain syndromes.


  • The health of the gut microbiome is critical for overall health and immunity. The gut can become leaky, meaning there are essentially tiny openings in the gut lining. This allows toxins and other unwanted substances to enter into the bloodstream.
  • Once this happens, the gut is now leaky or permeable. Leaky gut can lead to chronic inflammation. Chronic inflammation can lead to chronic diseases like autoimmune conditions, digestive diseases (IBD, IBS, etc.), Alzheimer’s, skin conditions and many others.
  • The brain is a complex organ that is surrounded and protected by the blood brain barrier or BBB.
  • The BBB is similar to the gut lining. It is made of tight junctions. These tight junctions can become loose and allow the BBB to become leaky or permeable. Once the BBB has become permeable, toxins, bacteria and other pathogenic substances can enter the brain. 
  • Leaky gut can cause leaky brain via the gut – brain axis. Via metabolic cross talk, any negative microbiome issues communicate with and travel to the brain via the gut – brain axis. 
  • Other pathogens, like environmental toxins, viruses and fungi, communicate or cross-talk as well, causing inflammation and other potential issues in the brain.

** Please continue to follow us for our next Blog on Leaky Gut & Brain!  **

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Dr. Miles has spoken for the following organizations:

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