There are links between gut and mood. In Beyond Digestion, I talk a lot about the fact that we not only have to digest our food, but also the world around us. When life gives us more than we can handle, it is literally “beyond digestion”, meaning life can be stressful, especially we lack the appropriate ways to cope.

Did you know? Of those with IBS, thirty percent seek treatment and in that thirty percent, ninety percent of the people have anxiety and or depression. But even those who don’t have IBS have issues with gut and mood. What’s going on?

Join Jennifer Smrtz and me in conversation about gut and mood.

What does stress do to our gut?

Stress, typically stimulated by the root element of fear, triggers the release of cortisol into our bloodstream. Long term cortisol release wreaks havoc on the body in numerous ways. In the gut, it reduces diversity of the microbiome, lowers our primary defense immunity (IgA), which increases the chance of infection and inflammation and changes the gastrointestinal microbiome byproducts .

  • reduces diversity within microbiome
  • lowers immune defense
  • increases chance of infection
  • increases inflammation
  • changes microbial byproducts which impact our mood
Amazon bestseller, Beyond Digestion as displayed at the Bookshelf store in Guelph

What are the byproducts of the gut microbiome?

Short chain fatty acids (SCFAs) are microbial byproducts of fermentation of dietary fibre. SCFAs are responsible to feed the cells lining the gut, regulate immune function, reduce inflammation. An imbalance SCFAs are associated with both depressive symptoms and gut symptoms in young adults.

Production of vitamins like folate, vitamin K, biotin, riboflavin (B2), cobalamin (B12), and possibly other B vitamins. B vitamins are critical in mood as they are needed in the breakdown process of of chemicals required for proper functioning in the body.

The microbiome also produces neurochemicals like GABA, acetylcholamines, histamine, melatonin, 5-HTP and serotonin. GABA calms us. Acetylcholamines excite us. Histamine, which needs to be balanced or there is a risk of anxiety, depression, OCD, or paranoia. Melatonin helps the gut lining heal and replenish itself and serotonin and it precursor 5-HTP help promote a happy mood and promote the movement of food along the digestive tract.

The bacteria in the gut also makes lipopolysaccaharides (LPS). In small quantities, LPS induces REM (dream state) sleep, and in large quantities is inflammatory. Think there is only such thing as a leaky gut? There is also something referred to as “leaky brain”. This is where the blood brain barrier, which is normally pretty selective what gets into the brain, is altered and becomes less selective allowing things to filer in and increase the chances of inflammation in the brain, a contributing factor to alteration in mood.

β-glucuronidase, an enzyme that deconjugates estrogens into their active forms. A lack microbiome diversity can lead to changed levels of β-glucuronidase and results in an alteration of circulating estrogens and may contribute to the development of obesity, metabolic syndrome, cancer, endometrial hyperplasia, endometriosis, polycystic ovary syndrome, fertility, cardiovascular disease (CVD) and, cognitive function.

  • short chain fatty acids (SCFAs)
  • lipopolysaccharides
  • histamine
  • GABA
  • melatonin
  • 5-HTP and serotonin
  • lipopolysaccharrides (LPS)
  • β-glucuronidase

I’m sure I’m just scratching the surface. It is clear, when it comes to good mood, there are many reasons why gut health matters.


Provensi G, Schmidt SD, Boehme M, Bastiaanssen TFS, Rani B, Costa A, Busca K, Fouhy F, Strain C, Stanton C, Blandina P, Izquierdo I, Cryan JF, Passani MB. Preventing adolescent stress-induced cognitive and microbiome changes by diet. Proc Natl Acad Sci U S A. 2019 May 7;116(19):9644-9651. doi: 10.1073/pnas.1820832116. Epub 2019 Apr 22. PMID: 31010921; PMCID: PMC6511019.