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Someone recently asked me if small intestinal bacterial overgrowth (SIBO) causes leaky gut, and if so, will the Fast Tract Diet help correct it?”

SIBO is most definitely linked to leaky gut, and the connection goes a long way to explain why SIBO is linked to many autoimmune conditions including:

  • Celiac disease
  • Hashimoto’s
  • Rheumatoid arthritis
  • Ankylosing spondylitis

When leaky gut occurs, proteins, protein fragments, toxins, incompletely digested food particles, viruses, whole or fragmented bacteria and their waste products escape from inside the intestines where they come into contact with our immune system whose job is to identify, hunt down and destroy them. Unfortunately, the same immune response can trigger various autoimmune conditions in people who are genetically predisposed to them.

The proposed mechanism is “molecular mimicry” where these foreign proteins or other antigens resemble some of our body’s own proteins. Thus when they elicit an immune response, the reaction also targets our “self” proteins.

The most common test for leaky gut is the lactulose/mannitol small intestinal permeability test.  Intestinal permeability (IP) is the medical term for leaky gut. The test is based on the idea that while neither sugar is digestible, mannitol is efficiently absorbed into the blood stream (showing up later in urine) while lactulose, a larger molecule is not. But when the gut becomes leaky, lactulose can escape raising the ratio of lactulose to mannitol in the urine.

Using this test, a study in 1997 evaluated 34 subjects suspected of having SIBO and 34 asymptomatic controls. The subjects with SIBO exhibited increased IP.  Increased IP has also been observed in people with a variety of SIBO-linked conditions including fibromyalgia, celiac disease IBS, another IBS study, post infectious IBS, and Crohn’s disease.

While these studies don’t prove SIBO is the cause of leaky gut, the close association of SIBO with leaky gut and the types of damage caused by SIBO convince me that SIBO likely plays a causative role: therefore, the Fast Tract Diet makes sense for treating and preventing leaky gut.

In the case of celiac disease, the effect of the gluten-triggered autoimmune response that damages intestinal villi structures likely is an independent factor contributing to leaky gut – beyond SIBO alone. The best strategy for someone with Celiac disease is therefore a gluten-free version of the Fast Tract Diet since SIBO is also a big problem for celiacs.

For more information on our mucosal barrier, tight junctions and their regulation by a protein called zonulin, I recommend this great review by Anthony Fasano.