Leaky Gut Syndrome
Leaky Gut Syndrome

Leaky Gut Syndrome

By Charlotte Pitcher – Trainee Physiologist – FGC

Here at The Functional Gut Clinic, patients commonly ask us about ‘leaky gut syndrome’ and how this relates to IBS type symptoms.

Leaky gut is not something we diagnose, as it is not officially recognised as a diagnosable disease in modern medicine. However, many naturopaths cite leaky gut syndrome as a cause of many long-term health problems, from IBS to chronic fatigue and multiple sclerosis.

We investigated further to see if there is scientific evidence for these claims, or if the theory behind leaky gut syndrome has more holes than an intestinal wall.

What is a leaky gut?

In our bodies, our intestines are lined by a single layer of cells, joined together by proteins that make up tight junctions. In leaky gut syndrome these junctions are thought to become loose, and therefore allow toxins and bacteria to leak through into the bloodstream. Once in the bloodstream, the effects are thought to be widespread, causing leaky gut syndrome to be linked with diseases spanning the whole body, from Inflammatory Bowel Disease and Crohn’s, to heart disease and autism.

How does the gut become leaky?

Research into leaky gut suggests many different factors could cause a gut to become leaky, but it is most commonly thought to come following infection such as gastroenteritis. The theory behind this is that unwelcome organisms in the gut such as candida or E. coli can attach to the cells of the intestinal lining, interrupt the tight junctions between cells, and reduce barrier integrity. A further theory is that inflammatory molecules such as IFN-γ and TNF-α which are released as part of the body’s response to infection, cause reorganisation of proteins within these tight junctions and thus contribute to barrier breakdown. 

What’s the evidence?

Much of the evidence in favour of the leaky gut hypothesis relies on patient data following an episode of gastroenteritis (an infection in the gut). For example, a paper by Marshall et al, 2004 describes lactulose-mannose ratio (a measure of intestinal ‘leakiness’) to be significantly higher in people with post-infectious IBS. Despite this, levels of intestinal permeability classed as abnormal was not significantly more prevalent in IBS patients compared to controls. This suggests that although gut permeability may be higher in IBS patients post gastroenteritis, it does not mean that the intestinal permeability of IBS patients is any more likely to be abnormal or be causing problems.

As yet, therapies to restore gut barrier integrity, for example, liquorice root and bone broth, have not been shown in clinical trials to cure leakiness or the diseases it is purported to cause. Further human studies have also shown that loss of intestinal barrier function alone is insufficient to initiate disease. This suggests that although leaky gut may exist, it is not the root cause of disease, so treatment for this alone is unlikely to be of benefit.

The Gastrointestinal Society supports that intestinal permeability is not a root cause of diseases such as Crohn’s and celiac disease, but instead may be a symptom. Research suggests that in patients with celiac disease, abnormal permeability is a response to gluten ingestion, as in susceptible individuals, gluten can cause excess zonulin to be produced, which can then disrupt tight junctions. In 87% of people following a gluten-free diet for 1-year, intestinal permeability returns to normal levels.

How is leaky gut diagnosed?

There are several tests that can be used to diagnose leaky gut syndrome. One test looks at levels of different sugars in the urine, as large sugars such as lactulose would be unable to pass through the small gaps in a normal intestinal barrier, so the presence of this in urine could indicate that the barrier is impaired. Another analyses blood for levels of a substance called D-lactate which is low in healthy individuals, therefore high levels is thought to indicate intestinal leakiness. However, bacterial overgrowth can also cause D-lactate to increase, so diagnosis of leaky gut could be made when SIBO is the real culprit. Diagnosis of leaky gut syndrome is also commonly made following report of various non-specific symptoms, meaning the diagnosis is far from reliable.

Can a diagnosis of leaky gut improve my health?

Following a diagnosis of intestinal leakiness, the recommended treatments are varied. Some examples are bone broth and raw cultured dairy such as kefir, which are unpleasant to drink and remain unproven at improving leaky gut and associated symptoms. Other treatments include things like fibre, probiotics and reduced fat intake, which would likely improve your health, regardless of any leakiness. As it is, the treatments for leaky gut have little scientific data to support their use, and how they are expected to seal up any intestinal holes is unclear. This means that you could end up paying for supplements or special diets that do little to improve your leakiness and could even be dangerous. In addition, the non-specific nature of symptoms associated to leaky gut means that while your leakiness is being treated, the real cause of these symptoms could be a disease that remains undiagnosed and therefore untreated.

What’s the verdict?

Although ‘leaky gut’ as a phenomenon can be observed, it is unlikely that it is a significant cause of disease. Increased intestinal permeability alone has not been shown to result in disease, and similarly, disease cannot be cured by improving intestinal barrier function. Where intestinal permeability has been linked to diseases (such as Crohn’s or celiac disease) it is much more likely that this is as a symptom rather than a cause.

Functional practitioners may argue that a lack of supportive research does not necessarily mean leaky gut syndrome is not real. While this may be true, it remains that diagnosing and treating a disease that lacks sufficient research could be dangerous. At Functional Gut Clinic, we use methods that are strongly supported by scientific evidence to identify what is causing your symptoms, so a therapeutic strategy based on the best evidence can be developed for you.


  1. Marshall, J. K., Thabane, M., Garg, A. X., Clark, W., Meddings, J., & Collins, S. M. (2004). Intestinal permeability in patients with irritable bowel syndrome after a waterborne outbreak of acute gastroenteritis in Walkerton, Ontario. Alimentary Pharmacology and Therapeutics, 20(11–12), 1317–1322. https://doi.org/10.1111/j.1365-2036.2004.02284.x
  2. Arrieta, M. C., Bistritz, L., & Meddings, J. B. (2006). Alterations in intestinal permeability. Gut, 55(10), 1512–20. https://doi.org/10.1136/gut.2005.085373
  3. Debunking the Myth of “Leaky Gut Syndrome” | Gastrointestinal Society. (n.d.). Retrieved October 5, 2017, from https://www.badgut.org/information-centre/a-z-digestive-topics/leaky-gut-syndrome/
  4. Lopetuso, L. R., Scaldaferri, F., Bruno, G., Petito, V., Franceschi, F., & Gasbarrini, A. (2015). The therapeutic management of gut barrier leaking: The emerging role for mucosal barrier protectors. European Review for Medical and Pharmacological Sciences, 19(6), 1068–1076.
  5. Quigley, E. M. M. (2016). Leaky gut – concept or clinical entity? Current Opinion in Gastroenterology, 32(2), 74–79. https://doi.org/10.1097/MOG.0000000000000243
  6. Odenwald, M. A., & Turner, J. R. (2013). Intestinal permeability defects: is it time to treat? Clinical Gastroenterology and Hepatology : The Official Clinical Practice Journal of the American Gastroenterological Association, 11(9), 1075–83. https://doi.org/10.1016/j.cgh.2013.07.001