The Mind Gut Axis


You may have heard about how important probiotics are for your digestion, but did you know they can also affect other functions in the body, even in our brain? Let’s start with what probiotics are...

Probiotics are beneficial bacteria. The word probiotic is derived from the words pro which means ‘for’ and biotic which means ‘life’; therefore, the term 'probiotic' means supporting life. According to Health Canada “probiotics are considered to be live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.”[i]

Another term used to describe the bacteria living in our body, is called the microbiota. The microbiota in our intestines “is made up of around 100 trillion microbial cells encompassing at least 300 species.”[ii] This means that our intestinal bacteria outnumber the human cells in our bodies by ten times![iii] Or to look at it another way “the number of genes in the intestinal microbiome is one hundred-fold greater than the total genes in the host.”[iv] It may seem strange to think that you have more bacterial genes in your body than your own genes, but this is why a human being is now being perceived more as a super-organism.

What Do Probiotics Do?
Research is showing that probiotics affect many different areas within the body including:

  • Helping to digest carbohydrates[v]
  • Providing B vitamins[vi]
  • Fighting off bacteria and viruses[vii]
  • Helping with our immune system[viii]
  • Helping with IBS[ix] & intestinal bowel disease symptoms[x]
  • Affecting behavior and cognition[xi]

How does this affect our brains?
It turns out that our digestive system and brain regulate each other, through several different pathways. This back and forth communication between the digestive system and the brain is called the gut-brain axis.[xii]

Our brain helps regulate what happens in our digestive system through the enteric nervous system. This includes moving food through the digestive tract, mucous secretion, absorption of nutrients, and blood flow. Research is now showing that it also works the other way around. That the gut can affect brain function and behaviour through this same enteric nervous system.¹²

So how does this work?  
It goes back to the ability of the microbiota to affect our immunity. The intestines contain the most lymphoid tissue in the human body, which is called the gut-associated lymphoid tissues or GALT. The main purpose of these tissues is to protect the body from an invasion of bad bacteria. Many of these GALT immune cells are able to cross the blood-brain barrier, where they can then directly modify the activity of the immune cells that normally reside in our brains, as well as affecting neurons in the brain.¹²

Links have been found between mental health symptoms and bowel disorders, which has interested researchers into studying the gut-brain axis. Over 50% of IBS patients also have anxiety or depression[xiii] and “abnormal anxiety levels are found in up to 40% of patients with inflammatory bowel disease.”[xiv] Overall, the microbiota is an exciting new frontier in health, with research being published daily showing effects on our digestion all the way to our thoughts and emotions.

--- Sources

[i] Health Canada. Questions and Answers on Probiotics. Accessed March 15, 2019

[ii] Chung HJ et al. (2018). Metabolomics and Lipidomics Approaches in the Science of Probiotics: A Review. J Med Food. Nov;21(11):1086-1095.

[iii] Ince MN et al. (2016). Understanding Luminal Microorganisms and Their Potential Effectiveness in Treating Intestinal Inflammation. Inflam Bowel Dis Jan;22(1):194-201.

[iv] Walker WA. (2017). The importance of appropriate initial bacterial colonization of the intestine in newborn, child, and adult health. Pediatr Res. Sep;82(3):387-395

[v] Han Y.R. et al (2014) Production of α- and β-galactosidases from Bifidobacterium longum subsp. longum RD47. J Microbiol Biotechnol. May;24(5):675-82

[vi] Arreola, S.L., et al. (2014). Two β-Galactosidases from the Human Isolate Bifidobacterium breve DSM 20213: Molecular Cloning and Expression, Biochemical Characterization and Synthesis of Galacto-Oligosaccharides. PLoS. 9(8): e104056.

[vii] Ren, DY,  et al. (2013). Lactobacilli Reduce Chemokine IL-8 Production in Response to TNF-α and Salmonella Challenge of Caco-2 Cells Biomed Res Int. : 925219.

[viii] Liu Y  et al. (2018).Probiotics in Autoimmune and Inflammatory Disorders. Nutrients.  Oct;10(10):1537.

[ix] Didari T et al. (2015). Effectiveness of probiotics in irritable bowel syndrome: Updated systematic review with meta-analysis. World J Gastroenterol. Mar 14;21(10):3072-84.

[x] Alagon Fernandez Del Campo P et al. (2019). The Use of Probiotic Therapy to Modulate the Gut Microbiota and Dendritic Cell Responses in Inflammatory Bowel Disease. Med Sci (Basel). Feb 22;7(2). Pii:E33

[xi] Stilling, R.M., Dinan, T.G., and Cryan, J.F. (2014). Microbial genes, brain & behaviour - epigenetic regulation of the gut-brain axis. Genes, Brains and Behav. Jan;13(1):69-86.

[xii] Kim N et al. (2018). Mind-altering with the gut: Modulation of the gut-brain axis with probiotics. J Microbiol. Mar;56(3):172-182.

[xiii] Kim YK Shin C (2018) The Microbiota-Gut-Brain Axis in Neuropsychiatric Disorders:Pathophysiological Mechanisms and Novel Treatments. Curr Neuropharmacol. 16(5):559-573.

[xiv] Bannaga AS Selinger CP (2015). Inflammatory bowel disease and anxiety: links, risks and challenges faced. Clin Exp Gastroenterol Mar 23;8:111-7.