Image
If you have irritable bowel syndrome, you might also experience depression and other mental health issues. That’s because what happens in the gut doesn’t always stay in the gut. Sometimes it travels northwards.
Irritable bowel syndrome (IBS) is an umbrella term, meaning there’s something wrong in your gut, but that something remains elusive. IBS can’t be identified by tests, which usually suggest there’s nothing wrong with you. You haven’t got coeliac disease, Crohn’s or a stomach ulcer. Nor do you have cancer. Which is great, but doesn’t help with your recovery. You’re not imaging that bloated abdomen, or all that gas and discomfort.
“Leaky gut” may sound comically implausible, but call it intestinal permeability and it suddenly assumes the gravitas it demands. Just like IBS, intestinal permeability (IP) remains an enigma to many medics. It’s not considered a medical condition (possibly because there are no drugs to treat it), so it usually passes straight under the radar.
IP means that the gut lining, aka epithelium, has been compromised. The epithelium has two main functions: to allow the passage of digested nutrients and fluids to cross into the blood, and to stop unwanted intruders from doing the same. It’s an important barrier between your insides and the outside world.
This barrier consists of just one layer of cells. Holding those cells together are links called “tight junctions”.
When working properly those tight junctions are like nightclub bouncers, sifting out and blocking the riff raff. But if they become damaged, they lose their tightness and microscopic holes appear. Toxins, bacteria, undigested food, tiny bits of things that fell on your plate… in they pile.
IP is a potential cause of IBS. In fact, “Barrier dysfunction is present in a significant proportion of patients with IBS.”
But that’s just the start of it. With access all areas, the fallout of this mayhem can show up anywhere. So too can symptoms: as well as irritable bowel, you may experience joint pain, headache, depression, fatigue, food sensitivities, and recurrent infections.
What does this mean for the brain?
Like the gut, the brain has its own protective shield, called the blood–brain barrier (BBB). And like the gut epithelium, the BBB is comprised of just a single layer of cells, held together by tight junctions.
“A dysfunction of the blood brain barrier leading to a ‘leaky brain’ can be linked to various neurological diseases, including autistic spectrum disorder (ASD), dementia, Alzheimer’s disease, depression, and schizophrenia”
Its role is to be selective about what can pass into the brain and to block harmful substances, including heavy metals, bacteria, viruses and environmental toxins. When the BBB is damaged, and security breached, the brain is left vulnerable to attack.
Increased permeability of the BBB is a well-known phenomenon in neuroscience. What causes a leaky gut can also cause a leaky brain. At the top of the list, in both cases, is inflammation.
The typical modern, processed diet creates damage and dysbiosis. Part of the immune system’s response to damage in the gut is the release of pro-inflammatory chemicals called cytokines. These cytokines travel in blood, disrupt the BBB and weaken the tight junctions, increasing permeability and allowing undesirable substances to enter the brain.
Inflammation and depression
“Diet-related inflammation can promote depression, and diet-linked depression in turn heightens inflammation.”
There is growing evidence that cytokines and other substances created by inflammation in the gut can trigger clinical depression (also known as major depressive disorder, or MDD). So much so that in 2008 Belgian researchers concluded, in a study published in the journal Neuroendocrinology Letters, that
“The results of the present study show that patients with MDD should be checked for the presence of leaky gut.”
According to data from the National Health and Nutrition Examination Survey, an extraordinary 47% of people with clinical depression also have heightened inflammation in the gut.
What causes leaky gut/leaky brain?
Keep reading with a 7-day free trial
Subscribe to Your Nutritionist Recommends to keep reading this post and get 7 days of free access to the full post archives.