The mouth and its microbiome – the gateway to digestion
Introducing the most underrated part of your digestive system
When we think about digestive health, we naturally focus on what’s happening beneath our bellies, but are we forgetting one of the most important steps in the digestive process?
Back track to the very beginning of digestion and you’ll find yourself at a very important yet underrated digestive organ; the mouth.
As the gateway to our digestive tract, the mouth (or oral cavity), is often considered a window into the health of our digestion. It is one of the few parts of the digestive tract that is visible and interacts directly with the outside world, making it an important part of our first line of defence. It is the place where we taste, chew and swallow our foods. And, as if that list of beneficial functions wasn’t enough, the oral cavity is also home to a unique community of microbes, known as the oral microbiome. Just like the gut microbiome, the oral microbiome plays an important role in maintaining health and, like most microbial communities, balance is key.
In summary, our mouth does a whole lot more than we give it credit for! So, let’s ‘digest’ the science and explore the role this important organ plays in digestive health and beyond.
The role of oral health in digestion:
The oral cavity performs many important functions when it comes to digestive health. For instance, the oral cavity supports the break-down of food in the following ways:
- Mechanical – through the act of chewing
- Chemical – through the secretion of salivary enzymes1
The combination of chewing foods and coating them with saliva, helps to kick off the digestive process, not only making food easier swallow, but also easier to break down by digestive organs further down the tract. Therefore, taking care of oral health can be seen as an important part of caring for your overall digestion.
The oral microbiome and its role in general health
In addition to performing the first steps in food digestion, the oral cavity is also home to the 2nd most diverse community of microbes in the body after the gut microbiome.1 The combination of microbe-friendly surfaces, such as bone and gums, in addition to frequent interactions with the outside environment, make the oral cavity the perfect habitat in which microbes can thrive.
One of the most well-established roles of the oral microbiome, is the regulation of tooth and gum health. A healthy and balanced oral microbiome, helps to keep pathogenic microbes at bay, thereby preventing the overgrowth of microbes that have shown to contribute to dental carries and gum health concerns.1 This part is important, as without healthy teeth and gums, chewing our foods can become significantly more difficult, thereby affecting digestion as well as the absorption of important nutrients in our foods.
Interestingly, recent research has also demonstrated that oral microbes and their metabolites can transfer to other areas of the body, such as the lower digestive tract, cardiovascular system and even the brain.1 This highlights that oral microbiome health is not only important for healthy teeth and gums, but also for general health and well-being.1,3
Supporting oral health with a healthy oral microbiome:
The oral microbiome is first established at birth and is then shaped by our unique genetic, diet and lifestyle habits throughout the journey from childhood, through to our senior years.3
Environmental factors such as diet, smoking, dental health, hygiene, stress and certain medications, all play an important role in determining the balance of microbes that live within the oral cavity.3 For instance, eating a diet high in sugars can lead to the growth of harmful bacteria that can damage teeth. The tricky part to caring for a healthy oral microbiome is preventing the growth of pathogenic bacteria without harming healthy bacteria. For instance, mouth wash has shown to prevent the growth of both good and bad bacteria.
To support a healthy, balanced oral microbiome, consider these helpful tips:
- Reduce sugar intake – including confectionary, sweet drinks, and hidden sugars such as those found in dried fruit. sauces, yoghurt and salad dressing
- Avoid smoking and excess alcohol
- Look after your oral hygiene by regularly brushing your teeth and have regular dental check ups
In summary, a healthy digestion starts with the mouth. Therefore, taking care of your oral cavity, and oral microbiome, is a great first step towards supporting your digestive health!
 Tenovuo J. Antimicrobial function of human saliva-how important is it for oral health?. Acta Odontologica Scandinavica. 1998 Jan 1;56(5):250-6.
 Park SY, Hwang BO, Lim M, Ok SH, Lee SK, Chun KS, Park KK, Hu Y, Chung WY, Song NY. Oral–gut microbiome axis in gastrointestinal disease and cancer. Cancers. 2021 Jan;13(9):2124.
This research was supported by National Research Foundation of Korea (NRF) Grants funded by the Korean Government (grant numbers NRF-2020R1C1C1003338 and NRF-2016R1A5A2008630 to N.-Y.S.) and by the Yonsei University Research Fund of 2021 (Yonsei Signature Research Cluster Program 2021-22-0017).
 Kilian M, Chapple IL, Hannig M, Marsh PD, Meuric V, Pedersen AM, Tonetti MS, Wade WG, Zaura E. The oral microbiome–an update for oral healthcare professionals. British dental journal. 2016 Nov;221(10):657-66.
 Bescos R, Ashworth A, Cutler C, Brookes ZL, Belfield L, Rodiles A, Casas-Agustench P, Farnham G, Liddle L, Burleigh M, White D. Effects of Chlorhexidine mouthwash on the oral microbiome. Scientific reports. 2020 Mar 24;10(1):1-8. This study was funded by research grants of the Northcott Devon Medical Foundation (UK), the Seale-Hayne Trust (Devon, UK) and the Institute of Health & Community (University of Plymouth, UK). The authors declare no potential conflicts of interest with respect to the authorship and/or publication of this article.
 Australian Institute of Health and Welfare. Oral Health and Dental Care in Australia. (AU): Australian Institute of Health and Welfare; 2022. (Updated 2022, cited 2022, December 14). Retrieved from https://www.aihw.gov.au/reports/dental-oral-health/oral-health-and-dental-care-in-australia/contents/introduction