Leaky gut syndrome (LGS), also known as intestinal hyperpermeability, is a condition caused by disruption of the normally efficient seal between the epithelial cells that line the gastrointestinal tract. This seal – a result of microscopic “tight junctions” between the individual cells – forms a highly selective barrier between the inside of the gut and the bloodstream.
Only those molecules that are actively transported or that can passively diffuse across the cells’ membranes are allowed to pass through the thin epithelial barricade.
However, when the tight junctions break down, substances that are usually kept inside the intestine are able to “leak” through. Bacteria and their toxins, incompletely digested macromolecules (proteins, fats, etc.), and other potentially harmful agents can gain direct access to the blood, where they ostensibly incite inflammatory and allergic reactions (the so-called “systemic inflammatory response”).
These foreign antigens are blamed for all manner of ills by doctors who treat LGS – mostly practitioners of alternative medicine – but many Western-trained physicians discount the idea that LGS is a true clinical entity.
Poor Nutrition May Be One Cause of Leaky Gut Syndrome
The purported causes of LGS are diverse: antibiotics, excessive alcohol consumption, intestinal parasites, caffeine, nonsteroidal anti-inflammatory medications, cytotoxic drugs (i.e., chemotherapy), radiation, and underlying immune dysfunction have all been incriminated.
An intriguing but as yet unproven theory suggests that poor nutrition also triggers LGS by inflicting widespread damage on the intestinal lining. This hypothesis is based on the notion that modern diets introduce toxic substances to the gut that it isn’t designed to handle.
Through the millennia, humans have acquired the ability to eat a wide variety of foods, despite the fact that most foods are loaded with foreign antigens that would make us ill if those antigens were injected directly into our bloodstreams. However, the immune cells in our gastrointestinal tracts have learned to “ignore” most of these antigens so nutrition can be obtained from our environs. This dampened immune response – known as “oral tolerance” – allows molecules that would otherwise be allergenic to pass through the gut.
Supposedly, sugars, refined foods, and other contemporary dietary anomalies challenge our guts' inherent immune integrity.
Leaky Gut Syndrome is Associated with Many Diseases
The controversy surrounding LGS springs from a lack of data that definitively support the role of intestinal hyperpermeability in human illness. Some degree of hyperpermeability has been documented in specific conditions (e.g., Crohn’s disease or celiac disease), but it isn’t clear in these instances if LGS is a cause or a result. (Hollander D. Intestinal permeability, leaky gut, and intestinal disorders. Curr Gastroenterol Rep. 1999 Oct;1[5]:410-6)
Furthermore, LGS is associated with certain medical conditions, such as burns or trauma, but this is clearly the result of acute injury, widespread inflammation, and multiple organ system insult. Once these patients recover, their intestinal hyperpermeability resolves.
Finally, intestinal hyperpermeability has been implicated in several acute and chronic pediatric diseases that probably have their origins in infancy, but this is a period when the gut is immature and the tight junctions are particularly susceptible to injury. (Liu Z, et al. Tight junctions, leaky intestines, and pediatric diseases. Acta Paediatr. 2005 Apr;94[4]:386-93)
So, even though intestinal hyperpermeability may play a role in some conditions, most conventional physicians don’t acknowledge that LGS is the cause of the many conditions for which it has been blamed:
- Autism
- Acne
- Allergies
- Inflammatory bowel disease
- Fibromyalgia
- Chronic fatigue syndrome
- Halitosis (bad breath)
- Migraines
- Insomnia
- Diabetes
- Skin rashes
- Asthma
- Lupus
- Multiple sclerosis
- Addison’s disease (adrenal insufficiency)
- Thyroiditis
- Vasculitis
- Rheumatoid arthritis
- Nutritional deficiencies
- Irritable bowel syndrome
Home Testing for Leaky Gut Syndrome is Unreliable
Practitioners who treat LGS offer testing kits that patients can use at home to see if their intestines are permeable to specific complex sugars. When the intestinal lining is intact, it allows some of these sugars to pass through while it sequesters others within the intestinal lumen.
Presumably, a person whose gut is hyperpermeable would have higher than normal amounts of the normally sequestered sugars in his or her bloodstream and, hence, in the urine.
This relative permeability of the gut to mannitol and lactulose is sometimes used to predict disease severity in Crohn’s patients or to evaluate healing in celiac disease.
Unfortunately, urinary excretion of mannitol, lactulose and similar substrates is sufficiently variable among healthy persons and between healthy persons and individuals with bowel disease to make home permeability tests unreliable. (Vilela E, et al. Gut permeability to lactulose and mannitol differs in treated Crohn's disease and celiac disease patients and healthy subjects. Braz J Med Biol Res. 2008 Dec;41[12]:1105-9)
Leaky gut syndrome has become a popular scapegoat for a myriad of conditions that may or may not be associated with intestinal hyperpermeability. As additional research is forthcoming, the contribution of LGS to autoimmune illnesses, nutritional deficiencies, autism, and other diseases will hopefully be clarified.
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