When our bowels get too permeable: a sign of digestive problems?

Aside from the oxygen we breathe, everything our body needs to survive and function comes from what we consume every day. Water, carbs and fatty acids provide the energy we need; amino acids help produce over 10,000 different proteins. A multitude of other nutrients, including lipids, vitamins and minerals, contribute to building hundreds of essential compounds and making sure they function properly.

There are also the less “nutritional” items, such as alcohol and many oral medications, as well as microorganisms and various toxic substances. Before they enter our bloodstream and reach the tissues where they will be used, all these compounds have to get through a highly selective barrier: the bowel wall.

Our bodies have a sophisticated system set up for crossing that barrier. The bowel wall is made of a single layer of cells, with many folds (microvilli) which increase the surface available for absorbing nutrients. Nothing gets through easily, in either direction. Nutrients have to be “digested” first to get through, while microorganisms are stopped by a protective mucous layer and by the vigilant immune system.

The bowel wall, however, is not completely a hermetic seal. There are tiny passages called tight junctions in between bowel cells. These structures control the passage of water, ions and small molecules, in both directions [3]. If those junctions become too permeable, they can let through larger molecules or microorganisms which would not usually get through and would stay in the bowel. Once they’re in our blood, these molecules or microorganisms can trigger inflammatory reactions which disrupt our bodies.

There is always a certain degree of permeability in our bowels: that’s normal and partially defined by our genes. However, in some well-known acute or chronic conditions, permeability becomes excessive. We see that in several conditions, such as Crohn’s disease or ulcerative colitis, which are both inflammatory bowel diseases.

More recently, a new idea has emerged: What if the bowel were to become too permeable, contributing to the development of a number of other chronic diseases? This hypothesis has become very popular, especially on social media, where “leaky gut syndrome” has been the topic of many posts. The phrases “increased intestinal permeability” and “bowel hyperpermeability” can also be seen.

Leaky gut syndrome may be associated with numerous medical conditions [4], including:

• Irritable bowel syndrome
• Inflammatory bowel disease (IBD) such as Crohn’s disease and ulcerative colitis
• SIBO (Small Intestinal Bacterial Overgrowth), meaning too great a concentration of bacteria in the small bowel
• Cardiovascular disease
• Obesity
• Celiac disease, a severe form of gluten intolerance
• Non-alcoholic fatty liver (hepatic steatosis), which may develop into cirrhosis of the liver
• Rheumatoid arthritis
• Diabetes
• Chronic fatigue
• Asthma
• Fibromyalgia
• Autism

Some people who may have this syndrome report symptoms such as [6]:

• Bowel problems: diarrhea, chronic constipation, gas or bloating
• Weakened immune system
• Headache, memory loss or difficulty concentrating
• Chronic fatigue
• Skin problems like acne or eczema
• Sugar cravings
• Mental disorders such as depression, anxiety and attention deficit disorder, with or without hyperactivity (ADHD)

The symptoms listed above do not appear in any medical textbooks. As a result – for now – leaky gut syndrome is not recognized as an official medical condition.

On the other hand, intestinal hyperpermeability is recognized by science and is associated with multiple medical conditions. What we don’t yet know is whether the increased permeability actually causes the disease, or whether it is in fact a consequence of the disease.

It is also very difficult to diagnose it accurately. The only relatively accessible tool which can measure bowel permeability partially is the lactulose-mannitol test, which does not have a great reputation [6,7]. Despite some limitations, [8] blood tests for zonulin, a protein which increases the permeability of tight junctions, has also been suggested as an assessment tool.

Since leaky gut syndrome is not officially recognized, the pharmaceutical industry has limited interest in developing a drug to restore normal bowel permeability. Even so, that limitation should not stop us from controlling what may be the main factor behind it emerging: poor nutrition!

Unsurprisingly enough, the recommendations for supporting proper bowel permeability are very similar to the recommendations for maintaining a healthy microbiome or relieving irritable bowel syndrome [9].

Here are a few simple habits to adopt [4]:

1. Eat high-quality fats: prioritize fatty fish such as salmon and avoid red or processed meat.
2. Prioritize fibre and prebiotic foods like beets and garlic.
3. Reduce added sugar intake.
4. Limit alcohol consumption.
5. Use some supplements: probiotics and prebiotics can support microbiota health, while L-glutamine is known to repair tight joints.
6. Prioritize a low-FODMAPS diet, limiting the fermentable sugars strongly associated with irritable bowel symptoms.

Even though leaky gut syndrome is not medically recognized, there is evidence that intestinal hyperpermeability may be connected with many physiological disorders. Today, this concept means that individuals struggling with hard-to-diagnose disorders are able to match a definition, even an incorrect one, to what ails them.

Our bowels are much more than a digestive organ: they impact our energy, immunity and comfort. When we take care of our gut with a balanced diet and physical exercise, we’re investing in our overall health and daily wellness. Leaky gut syndrome or not, our bowels deserve our full attention.