Leaky gut syndrome
Apart from its functions as a digestive/absorptive organ, the small intestine also acts as a barrier to prevent potentially damaging substances in the intestine from entering the bloodstream. These include bacteria, bacterial cell wall polymers, chemotactic peptides, bacterial antigens capable of inducing antibodies, and bacterial and dietary antigens which can form systemic immune complexes.
If the integrity of the gut becomes impaired, this may result in the enhanced uptake of large inflammatory molecules and pathogenic (disease-causing) bacteria. Some of the factors which may damage the gut wall include: chronic allergic inflammation, chronic irritation due to non-steroidal anti-inflammatory drugs, or chronic irritation due to dysbiosis, parasites, or to the continual presence of too much inadequately digested food. Alcoholism, cancer chemotherapy and Aids are also associated with increased gut permeability, leading to ‘leaky gut syndrome’.
The symptoms of this condition may be non-specific: swelling and bloating of the abdomen, symptoms of an increased toxic load on the liver, such as the development of food allergies and chemical sensitivities, and increasing symptoms of nutritional deficiency as nutrient absorption worsens. (Paradoxically, while permeability to large molecules may increase due to the increased porosity of intercellular junctional complexes, permeability to small molecules decreases due to atrophy of the microvilli). According to the scientific literature, increased gut permeability appears to correlate with a number of frequently seen clinical disorders, including:
- Allergic disorders
- Ankylosing spondylitis
- Chronic dermatological conditions
- Coeliac disease
- Crohn’s disease
- Food allergy
- Inflammatory bowel disease
- Inflammatory joint disease
- Rheumatoid arthritis
The permeation of water-soluble molecules through the intestinal mucosa can occur either through cells (transcellular uptake) or between cells (paracellular uptake). Small molecules such as glucose and mannitol readily penetrate cells and passively diffuse through them. Larger molecules such as disaccharides (e.g. lactulose, sucrose) are normally excluded by cells. Leaky gut syndrome can therefore be diagnosed by measuring the ability of mannitol and lactulose to permeate the intestinal mucosa. Mannitol serves as a marker of transcellular uptake, and lactulose, being only slightly absorbed, serves as a marker for mucosal integrity. To perform the test, the patient mixes pre-measured amounts of lactulose and mannitol and drinks the challenge substance. The test – which is available through nutritional therapists – measures the amount of lactulose and mannitol recovered in a 6-hour urine sample. Low levels of mannitol and lactulose indicate malabsorption. Elevated levels of lactulose and mannitol are indicative of general increased permeability and leaky gut syndrome. An elevated lactulose/mannitol ratio indicates that the effective pore size of the gut mucosa has increased, allowing larger molecules to access the bloodstream, where they are capable of provoking allergic reactions.
Iron deficiency anaemia may cause leaky gut syndrome in babies and young children. (Berant M et al: Effect of iron deficiency on small intestinal permeability in infants and young children. J Pediatr Gastroeneterol Nutr 14(1):17-20, 1992).