Leaky Gut and Intestinal Permeability Part 1 — Definition, Symptoms, and Causes

By: BioDesign Wellness Center Staff

July 12, 2018 | Category: Gut Health

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So much has been written about leaky gut that is has almost become a household phrase. “Hi Mom, how’s your leaky gut today?” Well, maybe it’s not that well established, but we can tell you that when our medical team started in practice, most doctors in the conventional medical field considered leaky gut to be holistic quackery. In fact, the Canadian Society of Intestinal Research (the GI Society) continues to claim leaky gut is a myth. (Although they do recognize “increased intestinal permeability in those who have Crohn’s disease, celiac disease, in individuals receiving chemotherapy, and those who have a high intake of bowel-damaging substances such as aspirin and alcohol.”)

Even though much of the conventional medical community is reluctant to recognize leaky gut as a legitimate medical condition (or insist that it is somehow different from “intestinal permeability”), we here at BioDesign Wellness are encouraged by the increased discussion in the research and online. It is an important topic for many people who are in need of a solution.

In this two-part series, we bring you up to speed on the basics. In this part, Part 1, we explain what leaky gut is and why it is so important to recognize, describe the symptoms, and explore the common causes and triggers. In Part 2, we delve into testing and treatment.

What Is Leaky Gut Syndrome?

Leaky gut syndrome (intestinal permeability) is a condition that occurs when the intestinal barrier breaks down, allowing antigens to pass from the intestines into the bloodstream. (An antigen is a toxin or other foreign substance that triggers the body’s immune response.) The same type of barrier system is in place for our lungs, brain, and urinary tract.

The intestinal barrier comprises three layers:

  • The mucosal layer
  • The epithelium
  • The lamina propria

The three layers are packed with mucus secreting immune cells and chemical messengers that interact in a delicate balance to maintain barrier integrity and overall health. The barrier is actually very thin — ranging in thickness from that of tissue paper to paper towel depending on the health of the mucosal tissue at any given time.

The cells that form the intestinal layer are broken down and replaced rather quickly — every three to four days. The cells comprising the intestinal barrier are quite sophisticated, producing enzymes, hormones, neurotransmitters, and plenty of immune cells.

When the intestinal barrier is healthy, it allows nutrients to pass through into the bloodstream while preventing the passage of any antigens. This protection is important because we come into contact with a barrage of environmental antigens, food antigens, and infectious agents on a daily basis. When we encounter certain triggers from foods, medications, bacteria, or environmental toxins, the intestinal barrier can become compromised, generating what is termed “leaky gut.”

Leaky gut sounds like a simple leak; just plug it up and then all is right. However, it’s not that simple. Leaky gut is better understood as a loss of integrity to the intestinal barrier that results in one or more of the following:

  • Malabsorption of nutrients
  • Immune compromise
  • Autoimmune activity
  • Intestinal distress

For our patients, we prefer a simpler explanation of leaky gut:

The army general is in charge of keeping a buffer zone between her troops and the killing fields. If the buffer zone is compromised, all hell breaks loose, and that is exactly what happens with leaky gut. When the integrity of the intestinal barrier is compromised, the immune system is easily aggravated, the intestines become inflamed, and, ultimately, we become malnourished even if we are eating properly. Deficiency in nutrients leads to cellular oxidation, inflammation, and further immune system dysfunction, setting the stage for the development of autoimmune responses where one or more systems are involved.

Symptoms of Leaky Gut Syndrome

The list of symptoms associated with leaky gut is staggering, and the connection between the condition and the symptoms is often obscure because symptoms do not always include gastrointestinal complaints. Here’s a list of symptoms and conditions we commonly observe in patients with leaky gut, broken down into various categories:

Gastrointestinal symptoms

  • Bloating, gas, distention
  • Indigestion or heart burn
  • Constipation or loose stools
  • Undigested food in stool
  • Foul smelling stools
  • Abdominal pain

Musculoskeletal symptoms

  • Waking up with muscle aches and pains
  • Stiff, sore or achy joints
  • Chronic pain or injury in the spine or extremities that fails to heal even with therapy and exercise

Brain-based symptoms

  • Headaches or migraines
  • Mood swings, anxiety, or depression (these can be general and not necessarily diagnosed conditions)
  • Brain fog
  • Loss of memory or acuity
  • Loss of motivation or drive
  • Restless or interrupted sleep patterns

Metabolic symptoms

  • Thyroid dysfunction leading to weight gain
  • Unexplained weight loss
  • Five to 10 pounds of weight fluctuations for unknown reasons

Immune symptoms

  • Chronic infections, such as sinus, urinary tract, vaginal, and respiratory infections
  • Autoimmune conditions, including rheumatoid arthritis (RA), Hashimoto’s (chronic lymphocytic thyroiditis), Lupus, and many others. Research shows a strong correlation between intestinal barrier breakdown (leaky gut) and autoimmune disorders.

A person with leaky gut often has a number of symptoms that are progressively worsening and is unable to find clear answers for their brain fog, indigestion, mood swings, and muscular or joint pain.

Common Causes/Triggers of Leaky Gut

The symptoms that may be related to leaky gut can be obscure because they are not always accompanied by gastrointestinal complaints. Therefore, it is important to consider what triggers leaky gut. The quantity and consistency of triggers a person is exposed to can help the doctor to determine if checking for leaky gut makes good clinical sense.

Common causes/triggers of leaky gut include the following:

  • Stress
  • Infection
  • Medications
  • Diet
  • Head trauma


We are all aware of the mind-body connection and the damage that emotional stress can have on our health. Stress directly causes aging — specifically, chronic unresolved stress as is common in relationships, workplaces, and families. Post-traumatic stress disorder (PTSD) is quite common and often overlooked as a root cause of many chronic health conditions. Ultimately, chronic stress leads to chronic diseases.

Our response to stress is chemical in nature. Under stress, we secrete stress hormones, most notably cortisol and adrenaline. Cortisol and adrenaline are secreted due to signals coming from the brain.

The stress hormones are responsible for trying to keep us functioning and alert during stress. The body requires more protein and nutrients. However, stress also turns off our relaxation response precisely when digestion occurs. As a result, we can’t efficiently digest the protein we consume when we are under stress, and we tend to eat more sugar and carbs.

So, what does this have to do with intestinal barrier health and leaky gut? Elevated stress hormones, particularly cortisol, signal the body to break down skeletal muscle and the lining of the gut (intestinal barrier) in an effort to provide the protein needed for energy, leading to muscle loss and leaky gut. Why would the body do that? It’s simply a survival mechanism to get more protein into circulation to use for energy and repair of vital organs — the heart and brain. During stress, the priority is not digestion or muscle building. Of course, this leads to the consequences of altered immune function and inflammation worsening the problem. Ultimately stress triggers and feeds a viscous cycle that robs us of our health and vigor.

During consultations with patients, we can often trace the onset of symptoms and health concerns to the timing of a stressful life event. While, the stressful life event may have passed, the damage from the elevated cortisol has never been resolved, and the person continues to suffer.


Chronic infections are often a reflection of the weakening of the immune system. Seventy percent of the immune system is located in the gastrointestinal tract in the form of Peyer’s patches (small masses of lymphatic tissue found throughout the ileum region of the small intestine). These patches are loaded with immune cells that are ready at all times to protect from the variety of invaders that would opportunistically enter through the mouth and into the gut.

This is often the first place to look for infection that could be causing inflammation and irritating the intestinal barrier. Again, here we have a potential vicious cycle, where the immune system in the gut has become compromised by a bacteria or parasite, which results in intestinal barrier dysfunction. The breakdown of the intestinal barrier further weakens the immune system and can now start to cause systemic infections or autoimmune reactions.

Infections can be found by running a specialized stool test looking for the DNA of infectious bacteria, parasites, or viruses. In addition, markers for inflammation and leaky gut can be viewed in the same specimen.


Medications that commonly cause or contribute to leaky gut include the following:

  • Antibiotics
  • Proton pump inhibitors (PPIs), such as Omeprazole, the “purple pill”
  • Non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen, and naproxen


The most common foods that can lead to or aggravate a leaky gut include the following:

  • Gluten: Gliadin proteins found in gluten are known to be reactive and inflammatory. In some people, Gluten triggers Celiac disease. For others it triggers an immune response that is not quite Celiac but creates inflammation in the intestinal barrier, which is classified as gluten sensitivity.
  • Dairy: Many people are not only lactose intolerant (i.e., lacking the enzymes to breakdown dairy), they also have allergies to the specific casein proteins in dairy. Again, this can trigger inflammatory responses at the intestinal barrier.
  • High fructose corn syrup: It feeds bad bacteria in the gut, leading to overgrowth of yeast and other unfriendly organisms that excrete toxins that can promote inflammation.
  • Foods with pesticides: The common pesticide Glyphosate (a.k.a., Roundup) has been shown to alter the microbial balance in the gastrointestinal tract, setting the stage for inflammation at the intestinal barrier.
  • Artificial sweeteners: These act as chemicals that can alter the gut microbiome, therefore impacting immune status in the gut and setting the stage for inflammation.
  • Alcohol: It weakens immunity and causes deterioration of the gut lining, acting as a toxin.

Head trauma

The brain and the gut have a direct line of communication, as is evidenced in the medical literature. A recent study published in the Journal of Neurotrauma entitled “Traumatic Brain Injury and Intestinal Dysfunction: Uncovering the Neuro-Enteric Axis,” points out that “traumatic brain injury (TBI) can induce an increase in intestinal permeability, which may lead to bacterial translocation, sepsis, and eventually multi-system organ failure.”

This is why it is so important for people who have any sort of head trauma to make sure that their physician is paying close attention to the integrity of the intestinal barrier, even if the patient has no symptoms of gastrointestinal (GI) distress.

If, after reading this post, you think some of the symptoms you are experiencing may be related to leaky gut, we encourage you to consult with a medical practitioner who has knowledge and experience with the diagnosis and treatment of leaky gut. If you happen to live in or near Tampa, Florida, come see us at the BioDesign Wellness Center.

In Part 2 of this series, which will publish next week, we cover the various tests available and our approach to restoring gut health and making our patients feel much better overall.

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Disclaimer: The information in this blog post — the first in a two-part series on Leaky Gut — is provided for general informational purposes only and may not reflect current medical thinking or practices. No information contained in this post should be construed as medical advice from the medical staff at BioDesign Wellness Center, Inc., nor is this post intended to be a substitute for medical counsel on any subject matter. No reader of this post should act or refrain from acting on the basis of any information included in, or accessible through, this post without seeking the appropriate medical advice on the particular facts and circumstances at issue from a licensed medical professional in the recipient’s state, country or other appropriate licensing jurisdiction.

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