Leaky Gut: Fact Or Fiction?

that there is an issue with intestinal permeability, the more technical name for “leaky gut.” About 75% of your entire immune system is located in your gut. Roughly 90% of your serotonin (a monoamine neurotransmitter) is also made in your gut.

This helps explain the link between a “leaky gut” and depression as well as a host of other conditions, like anxiety. How does your body protect you from “bad things”? Well, your intestinal wall has immune cells, which help protect against many harmful pathogens. Should this wall have issues, your liver is your next line of defense. If that doesn’t work, your body breaks out into a full-force response. It is within this series of events that “leaky gut” syndrome is linked.

Multiple sclerosis, diabetes, lupus, et. al. have all been correlated with a “leaky gut.” However, most importantly, all autoimmune diseases that have been tested, show intestinal permeability. Is this simply an effect of an autoimmune disease, or is it a cause of autoimmune disease? This is an important question, and one which will have widespread consequences in the medical community.

If microbes, toxins, undigested food and other substances can leak through, problems amount, or at least that’s what the theory proposes. But lets get to the heart, or should I say “gut,” of the issue. What does the scientific evidence say? And why is it to difficult to describe and prove this condition?


As stated in the scientific literature, “the major determinant of the rate of intestinal permeability is the opening or closure of the tight junctions between enterocytes in the paracellular space”. We know through the work of Alessio Fasano that zonulin plays an important role in the regulation of intestinal barrier function.

Fasano states that “when the finely tuned zonulin pathway is deregulated in genetically susceptible individuals, both intestinal and extraintestinal autoimmune, inflammatory, and neoplastic disorders can occur.” However, since zonulin itself was only discovered in 2000, how much do we really know about this protein?

Zonulin has been studied in those with and without diseases like celiac disease. Researchers conclude that “gliadin activates zonulin signaling irrespective of the genetic expression of autoimmunity, leading to increased intestinal permeability to macromolecules.” This means gluten (gliadin is one of the two main components of gluten) causes zonulin to open the walls of the intestine.

This is certainly interesting and is a very specific, proven, mechanism. The theory of a “leaky gut” becomes harder to counter with this knowledge in tow. Yet in science, healthy skepticism must remain. Unbiased research is the hallmark of maintaining integrity and credibility, so you cannot simply rush to the conclusion that “leaky gut” is fact based on just one study.

Other studies do show that gut peptides can influence brain function directly, however. This is sometimes referred to as the “gut-brain” axis. In more recent years, researchers have started looking into the exact mechanisms of the gut communicating with the brain. Researchers state that this occurs “possibly through neural, endocrine and immune pathways — and thereby influences brain function and behaviour.”

When one looks for facts of “leaky gut,” it is indeed a interesting search. There is quite a bit of dispute, some sides stating that it is an unproven condition with proponents simply taking advantage of health-compromised victims and using the theory as a platform to sell products. Is “leaky gut” fiction?


One needn’t look far for several sources claiming that “leaky gut” is nothing more than a hoax. This “Quackwatch” site lists “leaky gut” as a “fad diagnosis.” For those questioning the legitimacy of that article, it is written by a medical doctor. This site states that “the leaky gut theory is false.” The author lists these reasons to show that “leaky gut” may not be all that it’s cracked up to be. She states:

  1. It is impossible for large undigested food particles to pass through the many layers of cells into the bloodstream.
    2. The gut, nor the blood stream, is capable of selecting some large food particles which are allowed entry and not others.
    3. Food allergy tests cannot accurately detect allergenic foods.

Some authors  state that any link to autism and diet, specifically “leaky gut,” is all “quackery”. Yet this is countered by some researchers stating that gram negative bacteria, specifically lipopolysaccharides, make their way into the bloodstream. This is part of the development of a “leaky gut.” And other papers counter with the fact that mouse models support the role of the gut microbiota in predisposition to inflammatory conditions like rheumatoid arthritis.

And yet, still other sites state that “leaky gut” is merely a symptom. But what of all the anecdotal evidence? Clearly, there is not a single definitive answer, at least as of yet, in the world at large. Where you fall on the scale may be simply determined by your own reading and experiences.


New research shows that “leaky gut” indeed seems to be a real problem. In that article, “leaky gut” is potentially linked to asthma, irritable bowel syndrome, arthritis, and other problems. In fact, the Journal of Gastroenterology has an entry for “intestinal permeability.” Is the diagnosis simply condemned by mainstream medicine despite over 10,000 published articles that relate to its existence?

It is indeed a tricky topic and with so much anecdotal evidence, it is hard to ignore. As far back as 30 years ago, there has been a test for increased permeability of the intestine. Bacteria and gluten can cause the opening of the lining of the intestine. No one is debating that (hopefully).

Bacterial endotoxins (specifically from dead bacterial cell walls) also seem to cause activation of inflammatory pathways. In experimental animals, chronic low-grade endotoxemia causes the appearance of autoimmune disorders. Previously, molecular mimicry was one theory thought to explain the development of autoimmunity. Some literature disputes this, implicating that an increasingly permeable gut is the cause.

The causative nature of many autoimmune diseases remains elusive, and perhaps that is where the controversy stems. The medical community is oftentimes slow to change, especially with a theory that has for a long time been disregarded. Like many areas in alternative medicine, “leaky gut” may be a comforting name for a cluster of as-of-yet unexplained symptoms.

Signs Of A “Leaky Gut”

There are many different signs that link to a “leaky gut.” They are traditionally linked to IBS, gas, bloating, and/or diarrhea. Then there is the  link to acne, allergies, asthma, PMS, PCOS, autoimmune diseases, chronic fatigue, etc.

Since we are dealing with a large amount of issues, all supposedly related to one cause, the “quack” label begins to make sense. The same is true for gluten. However, there now seems to be enough medical and scientific literature to clearly show that there is merit to these claims.

How To “Fix” It

Probiotics are a good place to start, as well as removing inflammatory foods. Digestive enzymes may prove beneficial, and looking at certain diets, like the FODMAPs approach, or the GAPS diet, may also be beneficial.

As should be obvious, a Paleo approach is a great starting place. It is important to note that “leaky gut” can sometimes present as being more complicated than simply changing over from a SAD (standard American diet). Many factors will have to be dealt with, and the mere fact that it isn’t a medically recognized diagnosis makes things trickier. Even something as simple zinc supplementation has been studied to work in helping to heal a compromised intestinal lining.


As has been shown, “leaky gut” seems to definitely exist. Perhaps it is the causative nature of its link to autoimmunity that remains the brunt of the controversy. It also should be noted that in many cases, people are desperate for answers especially when they have crippling diseases.

There is some evidence for remission of conditions like multiple sclerosis when adopting a Paleo diet. However, is it the anti-inflammatory nature of the diet, or a favorable increase in balance of good bacteria, compared to bad bacteria, that is causing remission? There is no definitive answer to this question, perhaps maddeningly so.

Anecdotal evidence is important, especially in the discovering of new areas of science. But is there enough evidence to show that “leaky gut” causes autoimmune diseases? Maybe, maybe not. It really seems to depend on who you ask.

What is your opinion on “leaky gut”? Do you have any comments on whether it’s fact or fiction? Let us know!

This article originally appeared on PaleoHacks.