Leaky gut and mental health - What are the links?
The gut (a.k.a. digestive tract) is not just a tube that absorbs nutrients and gets rid of waste - it’s a complex alive system that’s a huge foundation of health. And not just gut health, but the overall health of our bodies and minds. We know how important it is to get all of our essential nutrients from food - and this is a big part of what our digestive tract does. But, there is way more to the story than just that.
When the gut is not working properly, symptoms can appear. Yes, typical gut and abdominal symptoms, but also other seemingly unrelated symptoms. Did you know that mental health issues have been linked with gut problems?
Let’s look at one gut problem in particular (you may have heard about this lately) - leaky gut. This literally involves tiny “leaks” in our gut lining that can allow more than just needed nutrients and water into our bodies. Researchers are looking at this, and I want to share the latest with you!
What is “leaky gut” linked with?
The “gut” is part of the digestive system, mainly the intestines, which are located in the abdomen. It’s an alive and very complex “tube” that acts as a gateway deciding what will enter the internal circulation of the body, and what must not get by. It digest and absorbs nutrients and water. It prevents toxins and “bad” microbes from being absorbed. And it shuttles all the waste to continue on and be eliminated.
You may think that symptoms of a leaky gut (a.k.a. “intestinal permeability”) are felt in the gut, and you’re right...to a point. Would you be surprised to know that lots of other symptoms and conditions are linked with leaky gut?
Leaky gut has been associated with:
● Autoimmune diseases (e.g. Type I diabetes, celiac disease, etc.)
● Inflammatory Bowel Diseases (e.g. ulcerative colitis, Crohn’s)
● Psychological stress and mental health
● And more!
Researchers are still figuring out the exact role that leaky gut plays in these conditions. Either way, the connections are there, and there are things that you can definitely do to improve your gut health. But first, how is our gut structured, and what can promote it to leak?
Gut structure - Three layers of our gut lining
Our guts have a three-layer lining that helps to allow things we need in, and keep harmful things out.
The first (outermost) layer is just one-cell thick. It’s a barrier that absorbs the nutrients and water we need, and physically prevents undigested compounds, toxins, and bacteria from getting in. Laid out flat, this layer makes up the largest surface area between the internal circulation of our bodies and the outside world (i.e. what we eat and drink).
The second layer is mucus. This mucus provides physical separation between the outermost enterocyte layer and the microbes and food that are inside the centre, or “lumen,” of the gut. It also contains special proteins that help fight against invaders. This mucus and its special compounds are produced by the enterocytes.
The third (innermost) layer inside our gut lining is our friendly resident gut microbes. Our guts contain billions of microbes - over 1 kg worth. Taken together, they’re sometimes referred to as a “superorganism.” These microbes include bacteria as well as other types of friendly microbes.
This layer of gut microbiota has two major functions to help promote a healthy gut lining:
● They crowd out “bad” bacteria by taking up space and eating the “good” food (i.e. fibre and resistant starch, which we’ll get into in a bit).
● They help to regulate the digestion and absorption of nutrients to nourish the first-layer enterocytes. One of the types of compounds they produce are called “short chain fatty acids” (SCFAs). These are considered to be anti-inflammatory and are also used as fuel for the enterocytes.
When the three layers aren’t working optimally, the tight junctions loosen, and leaks occur. This allows unwanted things to enter into the body’s circulation. This is how gut health affects our overall health.
Leaky gut and mental health
Stress and mental health issues are associated with inflammatory bowel diseases and leaky gut.
Stress hormones and moods can result in reduced levels of mood-boosting neurotransmitters in the brain and increase the risk of developing gut disorders, or flare ups of existing gut disorders. Several studies have found that patients with inflammatory gut conditions experienced worsening symptoms after stressful events. Chronic, or long-term, stress and depression is associated with more gut pain, leaky gut, and other inflammatory gut conditions like Crohn’s and ulcerative colitis. Stress can affect changes in the microbiota and the lining of the gut, and can further increase the gut inflammation. In animals, studies show that being under stress increases their intestinal permeability and inflammation.
We used to think that the brain sent direction down to control all parts of our bodies. We’re learning that a lot of the communication between the gut and the brain starts in the gut and goes up to the brain. Several studies show that in about half of people studied, gut symptoms arose before the mood issues did.
People who have gut disorders have a higher risk of developing anxiety or depression. Sometimes experiencing symptoms like abdominal pain, bloating, and discomfort can affect the quality of life and moods of people who have inflammatory bowel disease.
Some animal models of the inflammatory gut condition colitis promoted behavioural changes that are similar to mood disorders in people. Also, mice given an short chain fatty acid (SCFA) called butyrate seemed to experience an antidepressant effect.
These links between the gut and mental health are because of the “microbiota-gut-brain axis.” This axis includes many connections between the two of them, including through our nerves and hormones.
When the areas of the brain associated with stress are activated, this initiates the stress response. The stress response is twofold. First, it includes the release of stress hormones (hypothalamic-pituitary-adrenal axis - HPA axis) that go through the whole body. Second, it includes activation of the “fight or flight” (autonomic) part of the body’s nervous system. Both the hormones and autonomic nervous system affect the gut. And these can affect all three layers of the gut lining.
One of the key stress hormones of this HPA-axis is from the adrenal glands (the “A” in HPA). It’s the infamous stress hormone called cortisol. Cortisol is released into the bloodstream when we’re under stress. Cortisol directly affects the gut by reducing our ability to properly digest food, and instead prioritizes survival. It essentially prepares for “fight or flight” by slowing down the “rest and digest” functions.
FUN FACT: Mouse studies show that SCFAs may help to normalize the leakiness in not just our gut lining, but our “brain lining” (e.g. “blood-brain barrier”) too.
Leaky gut, or “intestinal permeability” is linked with many conditions of the gut, the body, and the mind. While research is still figuring out exactly how this happens and what comes first, there are definitely steps you can take today to help optimize your health. Learn how you can promote your gut health here!
Aguayo-Patrón, S. V., & Calderón de la Barca, A. M. (2017). Old Fashioned vs. Ultra-Processed-Based Current Diets: Possible Implication in the Increased Susceptibility to Type 1 Diabetes and Celiac Disease in Childhood. Foods, 6(11), 100. http://doi.org/10.3390/foods6110100
Brzozowski, B., Mazur-Bialy, A., Pajdo, R., Kwiecien, S., Bilski, J., Zwolinska-Wcislo, M., … Brzozowski, T. (2016). Mechanisms by which Stress Affects the Experimental and Clinical Inflammatory Bowel Disease (IBD): Role of Brain-Gut Axis. Current Neuropharmacology, 14(8), 892–900. http://doi.org/10.2174/1570159X14666160404124127
Fasano A. (2011). Zonulin and its regulation of intestinal barrier function: the biological door to inflammation, autoimmunity, and cancer. Physiol Rev. 91(1):151-75. doi: 10.1152/physrev.00003.2008.
Holtmann G, Shah A, Morrison M. (2017). Pathophysiology of Functional Gastrointestinal Disorders: A Holistic Overview. Dig Dis, 35 Suppl 1:5-13. doi: 10.1159/000485409.
Holzer, P., Farzi, A., Hassan, A. M., Zenz, G., Jačan, A., & Reichmann, F. (2017). Visceral Inflammation and Immune Activation Stress the Brain. Frontiers in Immunology, 8, 1613. http://doi.org/10.3389/fimmu.2017.01613
Kelly, J. R., Kennedy, P. J., Cryan, J. F., Dinan, T. G., Clarke, G., & Hyland, N. P. (2015). Breaking down the barriers: the gut microbiome, intestinal permeability and stress-related psychiatric disorders. Frontiers in Cellular Neuroscience, 9, 392. http://doi.org/10.3389/fncel.2015.00392
Lamprecht, M., Bogner, S., Schippinger, G., Steinbauer, K., Fankhauser, F., Hallstroem, S., … Greilberger, J. F. (2012). Probiotic supplementation affects markers of intestinal barrier, oxidation, and inflammation in trained men; a randomized, double-blinded, placebo-controlled trial. Journal of the International Society of Sports Nutrition, 9, 45. http://doi.org/10.1186/1550-2783-9-45
Lerner, A & Matthias, T. (2015). Changes in intestinal tight junction permeability associated with industrial food additives explain the rising incidence of autoimmune disease. Autoimmun Rev, 14(6):479-89. doi: 10.1016/j.autrev.2015.01.009.
Lerner, A., Neidhöfer, S., & Matthias, T. (2017). The Gut Microbiome Feelings of the Brain: A Perspective for Non-Microbiologists. Microorganisms, 5(4), 66. http://doi.org/10.3390/microorganisms5040066
Mu, Q., Kirby, J., Reilly, C. M., & Luo, X. M. (2017). Leaky Gut As a Danger Signal for Autoimmune Diseases. Frontiers in Immunology, 8, 598. http://doi.org/10.3389/fimmu.2017.00598
Slyepchenko, A., Maes, M., Jacka, F.N., Köhler, C.A., Barichello, T., McIntyre, R.S., Berk, M., Grande, I., Foster, J.A., Vieta, E. & Carvalho, A.F. (2017). Gut Microbiota, Bacterial Translocation, and Interactions with Diet: Pathophysiological Links between Major Depressive Disorder and Non-Communicable Medical Comorbidities. Psychother Psychosom, 86(1):31-46.
Sturgeon, C., & Fasano, A. (2016). Zonulin, a regulator of epithelial and endothelial barrier functions, and its involvement in chronic inflammatory diseases. Tissue Barriers, 4(4), e1251384. http://doi.org/10.1080/21688370.2016.1251384
Wikipedia. Bacteroidetes. Accessed May 22, 2018.
Wikipedia. Firmicutes. Accessed May 22, 2018.
Wilms, E., Gerritsen, J., Smidt, H., Besseling-van der Vaart, I., Rijkers, G. T., Garcia Fuentes, A. R., … Troost, F. J. (2016). Effects of Supplementation of the Synbiotic Ecologic® 825/FOS P6 on Intestinal Barrier Function in Healthy Humans: A Randomized Controlled Trial. PLoS ONE, 11(12), e0167775. http://doi.org/10.1371/journal.pone.0167775
World Health Organization, Food and Agriculture Organization. Probiotics. Accessed May 22, 2018.
Xiao, L., van’t Land, B., van de Worp, W. R. P. H., Stahl, B., Folkerts, G., & Garssen, J. (2017). Early-Life Nutritional Factors and Mucosal Immunity in the Development of Autoimmune Diabetes. Frontiers in Immunology, 8, 1219. http://doi.org/10.3389/fimmu.2017.01219