‘Leaky’ gut, or increased intestinal permeability (the medical name for leaky gut), is a condition that occurs when the lining of the gut becomes inflamed or damaged and fails to act as an effective barrier. It allows substances from inside the gut to move through the gut wall into places that it shouldn’t be.

Our gut is essentially one long tube, from the mouth to the anus, lined by a membrane (called the gut epithelium) that is just one cell thick. That lining looks different in different areas. In the intestines, for example, these cells have finger-like projections at the top, called villi. The membrane cells sit next to each other in a long row. In a healthy gut, the junctions between them are tight, to only selectively allow substances to pass through (like a security checkpoint!). In a leaky gut, the gut lining cells become inflamed or damaged and the tight junctions between them become loose, stopping them from being effective gatekeepers and allowing microbes, toxins and other substances to pass through. 

how does a leaky gut develop?

The epithelium of the gut has several mechanisms to keep it healthy. It secretes a layer of mucus to ‘coat’ the epithelium, and it also has special proteins forming the junctions between the cells, holding them tightly together – these act a bit like tightly pulled shoelaces. Zonulin is one of the proteins that helps to regulate these tight junctions. 

There is a lot of evidence that the gut microbiome (the trillions of microorganisms occupying the gut that help support the gut epithelium) secretes chemicals and proteins that can either provide nutrients to support the strength of the mucus layer, or secrete inflammatory chemicals that damage the gut epithelial cells. The gut immune system sits on the other side of these epithelial cells. It can become activated or damaged by toxins, increasing issues with the production of inflammatory chemicals. 

Many of the gut villains in our gut toolkit can contribute to leaky gut. Conversely, many of the gut heroes that we discuss have been shown to help heal a leaky gut. Dysbiosis (disruption of the microbiome) is one of the main factors that contribute to leaky gut (and prevents it from resolving). Stress, infection, inflammation, toxins and medications are other common causes.