The integrity of the gut wall is therefore critical to health and the body works hard to maintain its proper permeability in the face of considerable ‘assault’ on a daily basis. It is now recognised that this permeability, while remarkable in its complexity, is vulnerable and subject to change, depending on the integrity of the gut wall and the substances it is exposed to. Increased permeability, far from enhancing the transport of nutrients, opens the way for the entrance of toxins and improperly digested food particles which can give rise to a number of adverse conditions associated with ‘leaky gut syndrome’.
Symptoms and conditions associated with leaky gut syndrome:
- AIDS/HIV infection
- arthritis (osteo-/rheumatoid)
- childhood hyperactivity
- chronic fatigue syndrome
- chronic hapatitis
- chronic pancreatitis
- coeliac disease
- cystic fibrosis
- depression, mood swings
- food/chemical sensitivities
- inflammatory bowel disease (Crohn’s, ulcerative colitis)
- irritable bowel syndrome
- psoriasis, dermatitis
- urticaria (hives)
- viral, bacterial or yeast infection
The lining of the digestive tract is a remarkably complex ‘skin’ which performs countless functions - digesting foods, absorbing them, moving things along, providing immune protection and so on. Its folds, lined with villi, perform the seemingly contradictory task of acting as both a barrier to toxins and large food particles and a one-way, selective gate to nutrients. This careful balance is subjected to a host of toxins and allergens daily which, with optimum health of the mucous membranes, proper permeability, immunity, liver function and flora, pose no threat. If, however, any of these are compromised, ill health is likely to follow.
This highly selective permeability of the intestine is crucial to good health, yet it is a function that is particularly vulnerable to bad dietary habits and bacterial imbalances, which in turn may increase the production of toxins. It therefore has complex protection mechanisms, which consist of various substances secreted by intestines as well as its structure. This is designed such that nutrients are transported across the gut lining in one of two ways: either through the cells themselves (transcellularly) or through the gaps, or ‘tight junctions’ between the cells (paracellularly). It is when either or both of these mechanisms become faulty that the gut becomes increasingly permeable, or ‘leaky’ i.e. it allows the passage of unwanted substances across the gut wall.
The gut wall is protected by intestinal secretions which consist of, among other substances, protective mucus, immune cells that act as a benevolent police force, and secretory IgA. This is an immunoglobulin that acts like the bouncer in a nightclub. Each IgA molecule can remember what should or shouldn’t pass into the body, whistling up immune cells to get rid of unwanted guests. If IgA levels are very low this natural protection is lost.
What causes increased permeability?
The intestinal tract can become leaky for a number of reasons:
- Weakened immune system: if a person’s immune system is weakened with consequently low levels of secretory IgA - a common factor in prolonged stress - this can set the scene.
- Irritants to the gut lining: these include gluten in wheat, coffee, tea and many other allergy-provoking foods.
- Any deficiency of cell-building nutrients, like vitamin A, zinc, glutamine and essential fats, can result in a poor gut wall structure.
- An overgrowth of the wrong bacteria or fungi, such Candida albicans or any other parasite, can burrow into the intestinal wall, irritating it, causing increased permeability.
- Even abdominal distention, either as a result of bloating or over-eating can overstress the gut wall.
- Antibiotics, aspirin and other anti-inflammatory drugs are especially damaging to the gut.
Once gut permeability is increased, a vicious cycle may begin whereby the passage of toxins and undigested food particles into the body creates conditions which further exacerbate the situation: liver overload, malabsorption, allergy and dysbiosis.
Leaky gut - consequences or causes?
Ironically, once the liver becomes increasingly overloaded with toxins, toxic chemicals can be excreted in bile and re-enter the digestive tract, contributing to further intestinal damage1 . Also, the increased inflammation of the digestive tract actually stops the body absorbing health-promoting nutrients needed by the liver and needed by the body to produce digestive enzymes. It’s a vicious cycle in which leaky gut syndrome creates the conditions for leaky gut syndrome!2
The link between allergies and a leaky gut is another ‘chicken-egg’ situation in that each can give rise to the other. Allergies may manifest in a number of ways including eczema, fatigue etc. Some scientists propose that food allergies contribute to leaky gut syndrome in asthmatics due to an increased allergy load overwhelming the gut’s immune system3 . Dr Leo Galland, author of The Power of Healing, suggests that chemicals such as histamine, released in response to allergens, increase permeability. A number of studies have shown that people with food allergies have increased permeability in a fasting state which is further exacerbated when an offending food is ingested4 .
Dysbiosis - an imbalance of gut flora - is also a likely cause and consequence of leaky gut syndrome. Low stomach acid levels can also contribute since stomach acid normally destroys micro-organisms that can further damage digestive tract. It appears that increased permeability can even lead to the gut’s immune system over-reacting to normal gut bacteria as well as pathogenic organisms, once again increasing permeability.
Assessing gut permeability
As leaky gut has been implicated in many health problems, restoring the condition of the intestinal lining may be a key factor in improving digestive health. If you have any of the health problems listed above that have not responded to treatment, or if you score high on the common causes mentioned above, it is well worth your while finding out if you have increased intestinal permeability.
Testing for leaky gut syndrome
There are tests that can give a clear indication of how leaky or permeable the gut lining is. This is done by drinking certain chemicals that are not digested in the human body and then taking a urine sample to measure how readily they have got through the intestinal wall. Small molecules (e.g. mannitol) easily diffuse through cells while larger molecules (e.g. the disaccharide lactulose) do not normally pass across the intestinal wall. Mannitol can therefore be used to measure absorption through cells and lactulose acts as a marker for the integrity of the gaps between cells (tight junctions). So a gut permeability test involves the ingestion of particular amounts of these two molecules in a solution. Urine gathered over the next six hours is then measured for the levels of mannitol and lactulose and compared with a pre-test sample.
High levels of lactulose in the post-ingestion urine sample show that there is increased intestinal permeability or a ‘leaky gut’ while low levels of mannitol indicate that malabsorption of nutrients is a problem. A clinical nutritionist would be able to arrange such a test and interpret the results. See http://bant.org.uk.
Healing a leaky gut
Healing a leaky gut broadly involves three steps
- Remove the cause
- Improve gut flora and function
- Repair the gut
In order for the cause of leaky gut to be removed, it must first be detected. Factors to consider are drugs such as NSAIDs, alcohol, caffeine, allergy-provoking foods, Candida overgrowth or dysbiosis. Any improvement in intestinal health is unlikely while these are still present.
Meanwhile it is essential to provide the gut with an ample supply of the nutrients needed for good health and repair such as vitamin A, zinc, glutamine, essential fatty acids, antioxidants, n-acetyl-glucosamine and fibre. There are also several substances which can help improve gut function. The presence of friendly bacteria in adequate numbers is crucial in developing and sustaining a healthy gut. Probiotic supplements containing a range of bacteria including various Lactobacillus and Bifidus species can help this, especially when given along side FOS (fructooligosaccharides). It is important to ensure good digestion: from proper chewing and adequate levels of stomach acid to sufficient output of digestive enzymes. Each of these may be taken as supplements.
At the same time you should avoid suspected allergens (most probably wheat, gluten and dairy products), sugar, refined carbohydrates, saturated fat and meat ; and have plenty of water, fibre, water and nutrient-dense whole foods.
To find out more read my book Improve Your Digestion.
- Northrop-Clewes, C.A. and Downes, R.M., ‘Chronic diarrhoea and malnutrition in the Gambia: studies on intestinal permeability.’ Trans R Soc Trop Med Hyg vol 85(1), pp8-11 (1991)
- Sudduth, W.H., ‘The role of bacteria and enterotoxemia in physical addition to alcohol’ Microecology and Therapy vol18 (1989)
- Bernard, et al., ‘Increased intestinal permeability in bronchial asthma.’ Allergy Clin Immunol vol 97 pp1173-1178 (1996)
- Andre, C., et al., Ann Allergy vol 59(11), pp127-130 (1987) Andre, C., et al., Ann Allergy vol 44(9), pp 47-51 (1989)