- In the human body, there are as many bacteria as there are cells.
- The oral microbiome affects the health of the oral cavity as well as the heart and blood vessels.
What is the oral microbiome, and how does it affect health?
You've probably heard about the gut microbiome and its unmistakable impact on health. But the gut isn’t the only place in the human body where diverse strains of important bacteria are found, communicating and interacting on many levels. Bacteria also populate other parts of the body, including the skin, nose, private areas and mouth. Together, these microbial communities form a complex “organ” that plays a crucial role in supporting health and overall well‑being. Remarkably, the number of bacteria in the human microbiome is at least equal to or even higher than the number of human body cells.
The oral cavity is one of the most densely populated bacterial ecosystems in the body. Multiple bacterial habitats coexist within the mouth. For instance, some strains thrive in the gums, on the tongue, or on the cheek mucosa, while others prefer the surface of the teeth or the soft and hard palate. The oral microbiome is influenced by early childhood, with children born naturally and then breastfed having a significantly higher diversity of oral bacterial populations than children born by caesarean section or fed breast milk substitutes. The establishment of a complex microbiome occurs at about three years of age, with the diversity increasing with age. Significant changes in the oral microbiome also occur, for example, when milk teeth are replaced by permanent teeth.
The oral microbiome is an important component of the immune system, which not only prevents the development of dental caries or periodontal disease but also, for example, lesions, inflammation, and infections in the oral cavity or halitosis. But its influence doesn't stop there - many studies point to a link between imbalances in the oral microbiome and the development of cardiovascular disease.
What can negatively affect the oral microbiome?
- Nutrition: Foods high in simple sugars or carbonated, sweetened beverages (especially those containing acids) can lower the pH of the oral cavity, negatively affecting the oral microbiome. Research has also examined the impact of Neolithic and post‑Industrial Revolution diets, which introduced more cereals, legumes, dairy products, and vegetable oils. Some authors have suggested that these dietary changes may have contributed to a higher incidence of oral disease. However, these conclusions should be taken cautiously, as evidence from the Neolithic period is limited, and the mechanisms involved are not fully understood. It is not advisable to exclude these food groups from your diet, as they can be beneficial to overall health when consumed in moderation. The exception would be foods high in simple sugars and carbonated sweetened beverages, which should be limited.
- Smoking: Smoking negatively impacts the oral microbiome through various mechanisms. Components of cigarette smoke can directly kill beneficial bacteria, alter salivary pH, and create anaerobic conditions in the mouth so that some bacteria cannot survive. Smoking also weakens the immune response in the oral cavity and promotes the growth of pathogenic bacteria, disrupting the balance of the microbiome.
- Alcohol consumption: Excessive alcohol consumption affects the oral mucosa and the composition of saliva, potentially weakening the immune response in the oral cavity and compromising dental health. Finally, significant changes in the composition of the oral microbiome have been observed following alcohol consumption.
- Poor oral hygiene: Neglecting oral hygiene encourages the accumulation of plaque, creating an environment that promotes the growth of pathogenic bacteria and leads to an imbalance in the oral microbiome.
- Some diseases: Conditions such as diabetes, neurological disorders, cardiovascular issues, digestive problems, or autoimmune diseases can alter oral pH or weaken the immune response, both of which disrupt the oral microbiome.
- Some medications: The same situation applies to pharmaceuticals, particularly antibiotics or immunosuppressants.
What can have a positive effect on the oral microbiome?
The microbes in the oral cavity are nourished by substances contained in saliva or gingival fluid. Saliva also contains antibacterial components that help maintain the oral microbiome in balance. Saliva, together with other components, also forms a pellicle, which regulates the attachment of bacteria to the surface of the oral cavity or partially protects the teeth from the action of acids.
How to support the oral microbiome through diet
Diet significantly influences the balance of the oral microbiome by affecting the composition of saliva. An inadequate diet can lead to excessive production of caries‑causing acids, for example. However, the level of consumption of certain ingredients, such as nitrates, can also have an impact. In studies, it has even been observed that these changes can affect nitric oxide levels and blood pressure regulation. The immune response in the oral cavity may also be affected. At the same time, research in this area is still in its infancy, as it is a very complex issue.
A study from 2024 suggests that a Mediterranean‑style diet can positively influence the oral microbiome and thus reduce the incidence of oral diseases. High‑fibre foods and polyphenol‑rich beverages, such as coffee, black tea, and green tea, were shown to have beneficial effects. However, the study emphasises the need for further research, as lifestyle factors like physical activity also play a significant role.
The importance of adequate fibre intake is also supported by other studies, as is the consumption of minimally processed foods and whole grains instead of white flour products. Adequate hydration, which promotes normal saliva production, probably also plays a role. Potentially positive effects are also observed for the aforementioned nitrates, which are mainly derived from root or leafy vegetables.
It also appears that deficiencies of certain micronutrients, such as B vitamins (especially B12), vitamin C, vitamin E or vitamin K, may promote impaired oral health. Further research is needed on vitamins A and D.
How to support the oral microbiome with supplements?
There are already dietary supplements on the market to support the oral microbiome. In short, they should contain the probiotic strains mentioned below, especially Streptococcus (salivarius, ratus or thermophilus) and Lactobacillus (Lactiplantibacillus plantarum, Lacticaseibacillus paracasei, Limosilactobacillus reuteri). Among other substances, prebiotics such as xylitol, arginine or urea may also be beneficial.
Supplements that support the oral microbiome work mainly through three mechanisms:
- Competitive interaction between bacteria, which involves competition for food sources/subsistence.
- Production of antimicrobial or inhibitory compounds (inhibition = slowing down, dampening of processes)
- Modulation of the immune response
The following components, in particular, have a positive effect on the oral microbiome:
1. Probiotics
Probiotics are live bacterial organisms that form a direct part of the microbiome. For the oral microbiome, the most commonly studied genera include:
- Streptococcus: salivarius, ratus or thermophilus
- Lactobacillus: Lactiplantibacillus plantarum, Lacticaseibacillus paracasei, Limosilactobacillus reuteri
- Bifidobacterium: breve, lactis
- Bacillus coagulans
2. Prebiotics
Prebiotics are substances that beneficial microorganisms (probiotics) use as nutrients, promoting positive health effects. In the context of the oral cavity, prebiotics have been less extensively studied, as it is crucial to ensure they encourage the growth of beneficial bacteria without fostering pathogenic ones. However, certain compounds, such as xylitol, arginine, and urea, have shown promising results in studies.
3. Postbiotics
Postbiotics represent a cutting‑edge area of research in microbial colonisation and its impact on health. They are metabolites produced by living microorganisms or fragments of these organisms (e.g., cell walls, cytoplasm, etc.). For example, some studies have confirmed that postbiotics can inhibit the growth of pathogenic bacteria even in the absence of live beneficial bacteria, which could simplify storage and application processes. Examples of postbiotics include:
- Hydrogen peroxide
- Streptococcus bacteriocins (products of bacteria that can kill other bacteria)
Despite their potential, the effective use of postbiotics faces several challenges, particularly in product preparation. Ensuring that products retain the efficacy of live microorganisms without causing their death during processing is a significant hurdle. Studies have revealed that some commercial products contain insufficient numbers of viable cells, highlighting the need for further research in this area.
Bottom line
The microbial colonisation of the human body has implications for overall health, and the oral cavity is no exception. In particular, diet, smoking, alcohol consumption, poor oral hygiene, or certain diseases or medications have an impact on the composition and balance of the microbiome.
Research in this area is still limited, but it seems that minimally processed foods are beneficial for the oral microbiome, as is a sufficient intake of fibre, the components of which can be metabolised by bacteria. Some dietary supplements that support the oral microbiome are also already available on the market, but these products are currently facing many challenges.