Oral Microbiome and the Nervous System

We’ve spoken at length about the importance of the microbiome in our gut. In this blog we’ll examine another important but less wellknown collection of bacteria – those living in our mouth. These bacteria also play a crucial role in our health, particularly of our nerve and brain cells.

Oral Bacteria

It’s estimated we have over 700 species of bacteria residing in our oral cavity. As the entry to the digestive and respiratory tracts, these bacteria have the important job of protecting us from pathogenic bacteria from outside.

Just as in the gut, if the balance of the oral microbiome is disturbed, pathogenic species may take over if conditions aren’t right. Bacteria release signalling molecules and produce inflammation in the oral cavity. This may eventually contribute to inflammation and affect the health of the entire body because bacteria can easily access the bloodstream once they are swallowed.

An imbalance of the bacteria in the mouth is also associated with diseases such as rheumatoid arthritis, atherosclerosis, obesity and diabetes.

The Oral Microbiome and Oral Health

Imbalances in the oral microbiome contribute to the development of tooth decay, gingivitis and periodontal disease. Tooth decay is widespread throughout the world, affecting up to 90% people in industrialised countries. It’s caused when acids produced by oral bacteria destroy the enamel covering the teeth.

Plaque is a sticky substance containing millions of bacteria. If it’s allowed to build up on the teeth it can lead to gingivitis, characterised by gums which are swollen, inflamed and bleed easily. Over time gingivitis can develop into periodontitis or gum disease, which leads to weakening of the supporting structures of the teeth, resulting in tooth loss.

The Oral Microbiome and Brain Health

The link between oral health and brain and nerve health isn’t widely known. However, research which followed men over 30 years found a link between periodontal disease and tooth decay and decline in brain function. The more teeth lost through tooth decay the more cognitive function declined. It’s believed certain types of bacteria can produce molecules which are absorbed into the bloodstream and travel to the brain where they increase inflammation.

Another study looked at adults over ten years. Although their brains were normal at the start of the study, those with cognitive decline at the end of the study period had raised antibody levels to a specific type of oral bacteria, showing that the bacteria themselves can travel into the brain, probably by travelling up nerves which connect the teeth and the brain.

The Oral Microbiome and Alzheimer’s Disease

Specific types of oral bacteria associated with periodontal disease and gingivitis have been observed in the brains of Alzheimer’s sufferers.

Links have also been noted between periodontal disease and the presence of amyloid plaques in the brain, which are characteristic of Alzheimer’s disease. These are fragments of protein which may interfere with brain function.

The body appears to produce antibodies to the oral bacteria and these may boost amyloid production.  

The Link Between the Mouth and the Gut

The oral microbiome may also directly affect the gut, which as we know has far-reaching effects on our health.

Recent research discovered bacteria present in the mouth and those found in the faeces overlapped in almost half of people studies. So oral health and gut health are closely linked.

The oral bacteria can move into the gut and affect the immune system which resides there. One study examined what happened when the bacteria responsible for gingivitis was swallowed. Researchers found it led to an alteration in the balance of bacterial species in the gut, less bacterial diversity and an opening up of the junctions between cells in the intestinal lining, which results in leaky gut. It was also connected with increased chronic inflammation.

In this way it’s easy to see how what’s happening in our mouth can affect what’s happening in the entire body.

How to Support Your Oral Microbiome

From the above it is clear oral health is incredibly important for our overall health, particularly nervous system health. Sensible strategies to support your oral microbiome include:

Compared to our hunter-gatherer ancestors we eat a huge amount of carbohydrates, particularly sugar. It’s well known sugar causes dental caries, but it can also disturb the balance of your oral microbiome. Pathogenic oral bacteria need a steady stream of carbohydrates to survive, so it’s a good idea to avoid sugar as well as processed carbohydrates, which have had their fibre removed.

Smoking has been found to reduce oral bacterial diversity.

Alcohol reduces the levels of beneficial bacteria in the mouth.

If you would like to support your oral microbiome, you’ll need to look after your gut health too, as both are closely related.