Why the intestinal barrier is important

The intestine lining provides a barrier between the external environment and the internal environment of the body. Substances that are useful, like vitamins, fats and minerals, are absorbed into the body through the intestinal barrier. While substances that we don’t need or want are excreted.

We also share our intestine with microbes, like bacteria and fungi. It is estimated that 100 trillions microbes live in our intestine. Most of these microbes are friendly and work to our advantage producing vitamins like vitamin K2 and B1 and short chain fatty acids nourishing the intestinal cells. However, if we have an unbalanced microbiome, some of these microbes can be pathogenic and release substances that can be detrimental to our health, like lipopolysaccharides which derive from the wall of gram negative bacteria. An intact intestinal barrier prevents the absorption of these toxic substances.

What is leaky gut

However, the intestinal barrier is relatively delicate. It is formed by a single layer of epithelial cells that are bound together through tight junctions.  It is coated with mucous which provides a environment for friendly bacteria. These cooperate to keep the barrier intact and act as a first line of defence but nonetheless the barrier can be breached. When the intestinal barriers is damaged it is said that we have a “leaky gut” as substances that are not meant to enter leak through from the intestine into the bloodstream. As the intestine is a very busy place having to deal both with substances coming from outside (food) and bacteria living in it, a damaged barrier can be a threat to our health.

What can damage the intestinal barrier

The intestinal barrier can be damaged by several things:

• Lack of nutrients like zinc needed to keep the tight junctions working well or glutamine (an amino acid) providing fuel for the epithelial cells

• Food allergies or intolerances which can trigger an immune response leading to inflammation disrupting the integrity of the gut lining

• Chronic stress leading to increased cortisol, alterations of the microbiome, reduced gut motility and mucous production and increased inflammation, all things that can damage the tight junctions.

• Long-term use of some medications like NSAIDs (e.g. ibuprofen). NSAIDs can damage the intestinal barrier in several ways. For example by inhibiting molecules (prostaglandins) that produce mucus and bicarbonate to protect the intestinal lining, by altering the microbiome or by damaging the mitochondria or by inducing gastrointestinal ulcers.

Many other factors can damage the intestinal barriers like Coeliac disease, Inflammatory bowel disease, alcohol, candida, and small intestinal bacterial overgrowth.

What repairs the intestinal barrier

Repairing the intestinal barrier is essential for preventing and reducing leaky gut. One can act on several fronts to support a healthy intestinal barrier. One of the most important actions is to support a healthy microbiome. We can do so by optimising dietary fibre and increasing the intake of polyphenols, found in foods like berries and green tea. Another action is to increase immune defences by promoting immunoglobulins, in particular secretory IgA (sIgA). sIgA helps neutralize pathogens and prevents harmful bacteria from adhering to the mucosal surface. A third action is to make sure that we have adequate levels of nutrients that are essential for maintaining the integrity of the intestinal barrier and supporting overall gut health, such as zinc and vitamin D3. We also need to ensure that we have adequate levels of the preferred fuel for the enterocytes, the cells lining the gut, as they need to do extra work for the repair. Glutamine, found in foods like cabbage, provides energy to enterocytes. Finally, we can use herbs like slippery elm to form a protective coating over the gut lining, soothing irritation.