Got Gut Health? Part 2: Intestinal Permeability and “Leaky Gut”

by | Dec 22, 2022 | Featured | 0 comments

Leaky gut used to be a very triggering phrase. “Leaky gut? Total myth” is what you might have heard 5 or 10 years ago. While there’s still some folks out there who don’t believe it exists, by now we have an incredible amount of scientific literature not only confirming it’s existence, but also it’s potential systemic consequences and the importance of protecting your gut lining. 

It does indeed have systemic consequences as well; intestinal permeability and dysbiosis may be one of the primary sources of inflammation in the general population, besides excess fat tissue. This in turn, can increase risk of many different issues; particularly metabolic and cognitive. 

Post Layout:

  • What actually is “leaky gut”?
  • Why is it a bad thing?
  • What can potentially cause it?
  • Potential solutions

The Definition of “Leaky Gut” or Increased Intestinal Permeability

If you follow some of the more zealous health gurus on the internet, alot of them talk about “leaky gut” as if its this brand new finding that is the cause of all your health issues, why your father-in-law doesn’t like you, and probably why your dog ran away too. At least thats the type of fervor many people talk about it with.

A lot of these types of gurus are the reason the opposite side has surfaced; those completely writing off leaky gut, saying it’s unscientific and doesn’t exist. The only thing unscientific about it is the term. Leaky gut certainly does exist, although its more formally known as “increased intestinal permeability” or “intestinal barrier dysfunction” within the scientific literature.

Intestinal Permeability is Normal

To understand what it is, first you should understand intestinal permeability is a totally normal phenomena for everyone. It’s only when its highly increased and gets a little out of control that it becomes pathological. 

Let’s talk a bit about basic digestion first. First, food goes through digestive processes in the mouth with your teeth and saliva, and then stomach with acid and enzymes. From there it goes to the small intestine, which is where most absorption occurs.

Some things in food are absorbed by going into or through the actual intestinal cells, and some things are absorbed by going between the cellular space. What we’re mainly looking at is the latter. 

There are sets of proteins in between intestinal cells that regulate intestinal permeability very carefully, so when food is consumed, these proteins “relax” a little bit, increasing intestinal permeability slightly so that certain molecules can be absorbed, and after absorption is complete, they tighten up again. This normal level of intestinal permeability was actually found and precisely defined by the consensus of an expert panel in Frankfurt, Germany in June 2012, so pretty recently. 

When Intestinal Permeability Becomes Pathological

During pathologic instances of increased permeability, this function is deregulated in some way, shape, or form, and the space in between intestinal cells is open more than it should be, more often than it should be. 

Which is quite problematic for overall health. Firstly, the thing that caused the permeability function to break down probably isn’t doing the rest of your body any favors. We’ll dive into root causes in a little bit, but gut barrier dysfunction only really occurs in states where health is a lot less than optimal. 

Once it does happen, however, things can get into the bloodstream and circulation that we really don’t want. 

Consequence of Undigested Proteins Reaching the Bloodstream

One prominent example would be proteins that haven’t been fully digested. If you have increased intestinal permeability, there’s a good chance you have compromised digestion a bit further up the chain as well – Whether it be lower stomach acid or less enzyme secretion, which can result in proteins that don’t get fully broken down into their constituent amino acids. 

Normally, these types of things would pass right through the small intestine and either get fermented by large intestine bacteria or pass through in feces, but in the presence of increased intestinal permeability, these proteins can get into the bloodstream.

This is an issue because our body’s are used to seeing the individual constituents of these things in the bloodstream; amino acids from proteins, simple sugars from more complex carbs, etc. If a portion of an undigested protein makes its way through and into the bloodstream, the immune system basically recognizes it as a foreign invader and attacks it, causing inflammation (as inflammation is just the activation of the immune system). 

After a bit of time, the immune system can create antibodies to these foods, which is one way you can develop dietary sensitivities. You might have heard its possible to get dietary sensitivities to foods you eat over and over and this is one way that that can happen. The good news is, these are “false” food sensitivities which will go away once the gut heals. Note that not all dietary sensitivities develop this way, so you may still have some sensitivities that exist after you ameliorate the increased permeability. 

Consequences of Bacterial Components Reaching the Bloodstream

The next example, and the real issue when it comes to systemic inflammation, would be components of bacteria that reside within the intestine.

There are little pieces of bacterial cell walls called LPS or endotoxin and in the presence of increased permeability, these will make it from the intestine into the bloodstream in large amounts. LPS is widely known to be an enormous inducer of inflammation and oxidative stress, which could indeed potentially contribute to numerous chronic diseases developing. We do know that both elevated levels of LPS and increased intestinal permeability are present in many conditions: IBS, IBD (Crohns and Colitis), alcoholic and non-alcoholic liver disease, type 1 and 2 diabetes, chronic depression, obsessive-compulsive disorder, multiple sclerosis, lupus, and the list goes on and on. 

In some cases, increased intestinal permeability comes before the disease condition, in other cases it seems that the condition is causing the increased intestinal permeability. The minute details of which happens first hasn’t been fully hashed out for many of the conditions. 

Causes of Increased Intestinal Permeability


Psychological stress, for one, can certainly contribute. If something is coming in dietarily that is causing the gut barrier to break down, normally the immune system rushes in to repair these types of things. However, under chronic stress, the immune system is significantly downregulated and shows a shift in behavior in general, so the damage being caused to the intestinal barrier is outpacing the immune system’s ability to heal it. There are many other ways stress contributes, but we won’t dive into them so much here. 

Poor Diet

The obvious elephant in the room, and also one of the biggest causes. Processed foods contain numerous additives which have been shown to irritate the gut lining over time. Large boluses of fructose (amounts you’d see in high fructose corn syrup-sweetened beverages, not the amounts you’d see in whole fruit) have been shown to increase it. 

Western-diet style meals containing large amounts of saturated fat with simple sugars can cause this as well. Hyperglycemia, or chronic high blood sugar, is one of the most established causes of increased intestinal permeability that’s been seen over and over in studies, even independently of body fat levels. 

As we know, poor diet can result in other conditions like metabolic disease or cardiovascular disease, and the chronic low-grade inflammation from these can potentially be taking immune system resources away from repairing the gut. Gliadin, a component of gluten, causes increased permeability in everyone, but for some its normal amounts that don’t cause issues, and for others it becomes pathological. Alcohol in anything more than moderate amounts contributes over time as well. There are a lot more components to this. 


A healthy microbiome is actually a very strong regulator of intestinal permeability. A healthy microbiome creates short chain fatty acids, which contribute to the guts mucus layer, protecting it from irritation and other things that could potentially cause increased permeability. 

Some species of bacteria in a healthy gut actually directly upregulate the amounts of the proteins that are responsible for these tight junctions in between the cells. There are an incredibly large amount of metabolites that healthy gut bacteria produce that contribute to a healthy gut lining as well; these are termed post-biotics. 

Finally, drugs: NSAIDS, steroid medications, oral birth control, motrin, aspirin and other less common medications could contribute. 

Potential Solutions 

I’ll caveat this with the fact that going into a detailed gut protocol is out of the scope of this blog post, but let’s give some tips and considerations. 

First, if the person is obese/overweight and has glycemic dysregulation, you probably shouldn’t worry about targeting the gut first with an elimination protocol. Focus on getting rid of their metabolic issues through general lifestyle optimization: increased food quality (lower percentage of processed foods), weight loss, strength training, lots of movement, good sleep, reduced stress, etc, and in many cases this can get rid of leaky gut without targeting it specifically.

If someone’s not obese, still focusing on the basics like getting enough fiber from diverse sources, including fermented foods, making sure they’re getting enough hydration, and ensuring the vast majority of their food choices are from whole foods can certainly help.

If they have good blood sugar regulation, are a healthy bodyfat percentage, are eating mostly whole foods, and aren’t under-eating or chronically under-eating, then we may be looking at an elimination protocol, which we go very in depth about in our Functional Nutrition and Metabolism Specialization course. 


Chakaroun RM, Massier L, Kovacs P. Gut Microbiome, Intestinal Permeability, and Tissue Bacteria in Metabolic Disease: Perpetrators or Bystanders? Nutrients. 2020 Apr 14;12(4):1082. doi: 10.3390/nu12041082. PMID: 32295104; PMCID: PMC7230435.

Kaczmarczyk, M., Löber, U., Adamek, K. et al. The gut microbiota is associated with the small intestinal paracellular permeability and the development of the immune system in healthy children during the first two years of life. J Transl Med 19, 177 (2021).

Tim Vanuytsel et al. The Role of Intestinal Permeability in Gastrointestinal Disorders and Current Methods of Evaluation. Front. Nutr., 26 August 2021 |

Katayoun Khoshbin et al. Effects of dietary components on intestinal permeability in health and disease. Neurogastroenterology and Motility. 03 NOV 2020

Nikita Hanning et al. Intestinal barrier dysfunction in irritable bowel syndrome: a systematic review. Therapeutic Advances in Gastroenterology. First Published February 24, 2021.

Andrea Michielan, Renata D’Incà, “Intestinal Permeability in Inflammatory Bowel Disease: Pathogenesis, Clinical Evaluation, and Therapy of Leaky Gut”, Mediators of Inflammation, vol. 2015, Article ID 628157, 10 pages, 2015.

Fukui H. Increased Intestinal Permeability and Decreased Barrier Function: Does It Really Influence the Risk of Inflammation? Inflamm Intest Dis. 2016 Oct;1(3):135-145. doi: 10.1159/000447252. Epub 2016 Jul 20. PMID: 29922669; PMCID: PMC5988153.

Arrieta MC, Bistritz L, Meddings JB. Alterations in intestinal permeability. Gut. 2006 Oct;55(10):1512-20. doi: 10.1136/gut.2005.085373. PMID: 16966705; PMCID: PMC1856434.

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 Gastroenterol. 2014 Nov 18;14:189. doi: 10.1186/s12876-014-0189-7. PMID: 25407511; PMCID: PMC4253991.

Paray BA, Albeshr MF, Jan AT, Rather IA. Leaky Gut and Autoimmunity: An Intricate Balance in Individuals Health and the Diseased State. Int J Mol Sci. 2020 Dec 21;21(24):9770. doi: 10.3390/ijms21249770. PMID: 33371435; PMCID: PMC7767453.

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