FAST FACTS
GUT FACTS
13 truths about gut health everyone should know
95%
95% of our serotonin and 50% of dopamine is made in the gut with the help of our gut bacteria. Other neurotransmitters made in the gut include gamma-aminobutyric acid and acetylcholine1 .
100
Our gut houses 100 trillion bugs (that’s about three times the number of cells that make up the human body). Collectively, these bugs are known as the gut microbiome1 .
500
There are over 500 different species of bacteria living in our gut1 .
25%
Our stools are made of 25% bacteria (dry weight is up to 55%)2 .
Everybody has both good bugs (commensal bacteria) and bad bugs (pathogenic bacteria)1 .
Dysbiosis
We need more of the good bugs and fewer of the bad. An imbalance in favour of the bad bugs is known as ‘dysbiosis’1 .
A varied wholefood diet that includes both insoluble and soluble fibre supports a healthy and diverse microbiome3 .
Probiotics
The term ‘probiotics’ refers to both the good bugs that live in our gut and also to the supplemental form.
Prebiotics
‘Prebiotics’ refers to the ‘food’ that probiotics ‘eat’ – these are generally fibres that we eat as humans but can’t digest. The bugs do this for us. In turn, they provide an energy source for the gut cells5 .
Postbiotics
‘Postbiotics’ are the waste products of the gut bugs consuming fibre – short-chain fatty acids, vitamins (such as vitamins K and B12) and some enzymes6 .
Our microbiome plays a role in many aspects of our health – mood, mental health, immunity and our hormone and metabolic regulation4.
The enteric nervous system
The gut has its own nervous system – the enteric nervous system7 .
The enteric nervous system talks to the brain (gut–brain axis) via the vagus nerve7 .
References
1. Chen, Y., Xu, J., & Chen, Y. Regulation of neurotransmitters by the gut microbiota and effects on cognition in neurological disorders. Nutrients. 2021 Jun 19;13(6):2099.
2. Stephen, A.M., & Cummings, J.H. The microbial contribution to human faecal mass. Journal of Medical Microbiology. 1980 Feb 1;13(1):45-56.
3. O’Grady, J., O’Connor, E. M., & Shanahan, F. Dietary fibre in the era of microbiome science. Alimentary pharmacology & therapeutics. 2019 Mar;49(5):506-15.
4. Young, V.B. The role of the microbiome in human health and disease: an introduction for clinicians. Bmj. 2017 Mar 15;356.
5. Mohajeri, M.H., Brummer, R.J., Rastall, R. A., Weersma, R.K., Harmsen, H.J., Faas, M., & Eggersdorfer, M. The role of the microbiome for human health: from basic science to clinical applications. European journal of nutrition. 2018 May;57(1):1-4.
6. Martyniak, A., Medyńska-Przęczek, A., Wędrychowicz, A., Skoczeń, S., & Tomasik, P.J. Prebiotics, probiotics, synbiotics, paraprobiotics and postbiotic compounds in IBD. Biomolecules. 2021 Dec 18;11(12):1903.
7. Bonaz, B., Bazin, T., & Pellissier, S. The vagus nerve at the interface of the microbiota-gut-brain axis. Frontiers in neuroscience. 2018 Feb 7;12:49.
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