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Gut Series: What Is Leaky Gut?

Updated: May 4, 2022

| by Functional Medicine Practitioner, Dr. Mitchell Rasmussen, DC, CFMP |

Did you know that the tissue within your gut is largely replaced every 2-6 days? ¹

Your GI tract is home to some 100 trillion different microbial organisms, and many of them are absolutely necessary for you to properly digest your food. Some studies have shown that the gut microbiota contains at least 100x the genetic material as our own total human genome!² (... that means, technically, the BUGS outnumber US)

How about the idea that if we took out your GI tract (weird thought), its surface area would be similar to that of a tennis court?!³

Perhaps the most surprising fact about the GI tract is that it is merely ONE CELL LAYER THICK!³ Literally, there is just one epithelial layer separating the contents within the intestine from the underlying connective tissue and bloodstream.


Why does gut tissue get replaced so frequently?

This is just one protection mechanism built into our biology to remove damaged or infected cells; a common theme in the GI tract. Remember, we are asking a single layer of cells to protect us from all of the pathogens, parasites, and toxins ubiquitous in our foods. Additionally, we are also relying on this single layer of cells to help nutrients easily pass into the bloodstream following digestion. We are needing a lot from this single layer of cells!


What does the gut lining do?

Structure dictates function. We need quick access of nutrients to the bloodstream, while simultaneously we ask this tissue to selectively disallow harm-causing substances from passing through. It is kind of like we are asking somebody to keep talking while also asking them to stay quiet.

Often, this process isn’t happening as well as we might hope. You might have heard of this sexy new term: “Leaky Gut”. Essentially, when we discuss Leaky Gut (or its more “professional” term of “Intestinal Hyperpermeability”), we really are discussing a loss of tight seals in the spaces between each cell.

We liken these spaces between cells to little spot welds. These “spots welds”, aka “Tight Junctions”, are protein structures which interact with other proteins within the cytoskeleton of our cells.³ One of the most important roles of the Tight Junctions is in regulating the permeability (“leakiness”) of the intestinal epithelium. They regulate the barrier: allowing in the “good stuff” while keeping out the “bad stuff.”

When we lose the “tight seal”, we then begin to experience all of the manifestations associated with a loss of proper intestinal barrier function. It can look like poor oral tolerance, autoimmune dysfunction, brain fog, mood disorders, and general 'sickness'.

This barrier is a very complex environment, as you might imagine. Studies have shown how various dietary components are able to change the permeability of this tissue by modifying expression of certain Tight Junction proteins³. We need to think of the Tight Junctions NOT as some type of static barrier, but as a highly dynamic, highly variable structure which gets constantly remodeled due to interactions with external stimuli, such as breakdown products from our diet, as well as bacteria, both commensal (“good”) and pathogenic (“bad”).

The entry of nutrients, ions, and water into and out of our GI tract is regulated by the Tight Junctions; as well as is the restriction to entry of potentially harmful substances.


SO, What are some possible causes of loss of intestinal barrier function which can lead to “Leaky Gut Syndrome”?

Leaky Gut has a number of triggers. When working with a Functional Medicine practitioner, eliminating as many of these exacerbating pathways is important PRIOR to beginning a gut-healing protocol. We must address the thing making holes, before patching to fence; so to speak.

Notably, here are key things we seek to correct:

  • Food Allergies, Intolerances, Sensitivities - particularly when these are related to large dietary proteins like Gluten, Casein, or Soy! An elimination diet can help pinpoint which proteins may be the most problematic for you.

  • Infections, Pathogens, Toxins, Antibodies - a stool test can help show any underlying gut infections, pathogens, or parasites causing a disrupted environment. In the case of autoimmune disease or antibody production, we consider how molecular mimicry can play a role.

  • Blood Sugar Issues, Stress - there's a reason Blood Sugar Control is a one of our non-negotiables in the Functional Medicine journey. Poor blood sugar regulation (often related to stress) can have downstream effects on the health of the microbiome, dietary patterns, nutrient status, as well as immune system regulation.

Adapted from

>>The biggest thing to understand here is that, “Your Leaky Gut did NOT cause your Leaky Gut!”. The best gut-healing diet and supplement plan will likely only provide temporary relief unless you find the cause(s) of your Leaky Gut Syndrome. <<

Your Leaky Gut did NOT cause your Leaky Gut

Find the triggers, then remove those triggers while simultaneously giving your gut what it needs to heal. It is a constant process of adaptation between the Functional Medicine Team (that's us) and the patient (that's YOU). As you improve the health of the gut, downstream effects tend to improve! We cannot ignore the gut-brain axis in the context of whole body health.

Need Help with your Leaky Gut?

what is leaky gut functional medicine Denver

We're here for you.

We always start with a Comprehensive Functional Medicine New Patient Exam. During that appointment, you'll sit with both Dr. Rasmussen (a Functional Medicine Doctor) and Kate (a Certified Nutrition Specialist) to talk through your symptoms, your diet, your lifestyle, and what you've tried. We'll order Functional Lab Testing and get started healing intestinal permeability.


Leaky gut protocol functional nutrition
A Leaky Gut Protocol doesn't have to be boring!



CLICK HERE to shop our supplement store - products are also available in our Cherry Creek Clinic.

If you're curious about building a personalized supplementation protocol for controlling and managing your gut health, contact us to book a consultation! (This can be remote).



1. Mayhew TM, Myklebust R, Whybrow A, et al. Epithelial integrity, cell death and cell loss in mammalian small intestine. Histol Histopathol. 1999;14 (1):257–267.

2. Qin J, Li R, Raes J, et al. A human gut microbial gene catalogue established by metagenomic sequencing. Nature 2010;464:59‐65.

3. Dulantha Ulluwishewa, Rachel C. Anderson, Warren C. McNabb, Paul J. Moughan, Jerry M. Wells, Nicole C. Roy, Regulation of Tight Junction Permeability by Intestinal Bacteria and Dietary Components, The Journal of Nutrition, Volume 141, Issue 5, May 2011, Pages 769–776,

4. Bischoff SC, Barbara G, Buurman W, Ockhuizen T, Schulzke JD, Serino M, Tilg H, Watson A, Wells JM, Intestinal Permeability – a new target for disease prevention and therapy. BMC Gastroenterology. 2014. Nov 18; 14: 189


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Dr. Mitchell Rasmussen - Doctor of Chiro
Kate Daugherty - Nutritionist - Function
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