Leaky Gut and the Blood Brain Barrier (BBB)


What Leaky Gut Is

The terms “leaky gut” and increased intestinal permeability refer to the same thing, and the idea is this: the junctions in your small intestine ought to be tight enough that nothing can get in or out unassisted. In a leaky gut, the junctions are loose enough that food particles can come in contact with the bloodstream prematurely (before they’ve been broken down into something your bloodstream would recognize and be able to use). Your blood therefore thinks the food particles are foreign invaders, and it creates antibodies against them. Symptoms in most cases mimic those of Irritable Bowel Syndrome, and include food sensitivities, gas and bloating, alternating constipation and diarrhea. Almost universally, a disrupted intestinal barrier will also have an abnormal microbiome.

But research now shows that symptoms of Leaky Gut Syndrome might look entirely different from the classic IBS presentation. In fact, Leaky Gut may be one of the underlying causes in illnesses involving disruption in the Blood Brain Barrier (BBB). These conditions can present with neurological symptoms, cognitive distortion, mood disruption, and even myelination disorders.

What the Blood Brain Barrier (BBB) Is

Like the tight junctions in the small intestine, the Blood Brain Barrier protects the brain from toxins and pathogens that might be circulating in the bloodstream, but grants entry to things like nutrients, oxygen, and glucose.

The gut certainly influences the Blood Brain Barrier by means of GI-derived hormonal secretion, allowing amino acids and some drugs to cross the BBB, and also influencing the secretion in the Central Nervous System (CNS) of cytokines, the inflammatory arm of the immune system. But a number of studies also show that the microbiome can directly affect the BBB. In fact, this study directly shows that an unhealthy microbiome can lead to increased BBB permeability, while a correcting the microbiome causes the BBB to “tighten up.”

The BBB and Demyelination Illnesses (Multiple Sclerosis, Autism)

Since the gut can alter production of inflammatory cytokines within the CNS, it’s not surprising that there may be a connection between autoimmunity in the CNS and the gut microbiome. Myelination (the fatty covering on nerve cells) is also influenced by gut microbes, and investigations are currently underway regarding possible connections between the microbiome and Multiple Sclerosis.

Autism has also been characterized by myelination changes in the Prefrontal Cortex (the part of the brain associated with executive functioning), and this study shows that autism is 1) characterized by a disrupted BBB, and 2) usually also characterized by increased intestinal permeability. Microbiota therapy may therefore soon be an official recommendation for autism.

The Upshot

If you or someone you love suffers from a neurological disorder, even if there are no apparent gut symptoms, testing for intestinal permeability and balancing microbiome may be therapeutically helpful.

To find out what is causing your gut health issues, take the Gut Health Quiz. It’s free!


  1. https://www.ncbi.nlm.nih.gov/pubmed/19805376
  2. https://www.ncbi.nlm.nih.gov/pubmed/22992437
  3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2553040/
  4. http://stm.sciencemag.org/content/6/263/263ra158
  5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4716932/
  6. https://www.ncbi.nlm.nih.gov/pubmed/22992437
  7. https://www.scientificamerican.com/article/the-tantalizing-links-between-gut-microbes-and-the-brain/
  8. http://www.dana.org/Media/GrantsDetails.aspx?id=38924
  9. https://www.sciencedaily.com/releases/2017/01/170118145937.htm
  10. https://www.ncbi.nlm.nih.gov/pubmed/27045844
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Dr Lauren Deville, NMD
Naturopathic Medical Doctor at Nature Cure Family Health