The Oral Microbiome: Why What Happens in Your Mouth Doesn’t Stay in Your Mouth
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The Oral Microbiome: Why What Happens in Your Mouth Doesn’t Stay in Your Mouth
When we think about oral hygiene, most of us focus on the obvious: avoiding cavities, keeping our breath fresh, and maintaining a good-looking smile. But the health of your mouth runs far deeper than aesthetics. Inside your oral cavity lives a vast and sophisticated community of microorganisms (bacteria, fungi, viruses, and archaea) collectively known as the oral microbiome. And the balance of this community has far-reaching consequences not just for your teeth and gums, but for your heart, your brain, your immune system and your metabolic health.
Understanding the oral microbiome, what disrupts it, and how to support it is one of the most underappreciated pillars of holistic health.
What Is the Oral Microbiome?
The mouth is the entry point between the outside world and the rest of your body, and it is home to an astonishing diversity of microbial life. With over 700 known bacterial species, the oral microbiome is the second most diverse microbial community in the human body, after the gut. These microorganisms colonise the teeth, tongue, gums, cheeks, and saliva, each niche hosting its own distinct microbial profile.
Under healthy conditions, the oral microbiome exists in a state of balance (known as eubiosis) with beneficial bacteria performing critical functions: helping to protect the enamel from acid erosion, producing antimicrobial compounds that suppress harmful pathogens, and priming the immune system. Much like the gut, the oral microbiome has coevolved with humans over millions of years and is an integral part of our physiology, not merely a bystander.
However, when this balance is disturbed (a state called dysbiosis) opportunistic and harmful bacteria can proliferate, driving both local and systemic disease.
What Factors Disrupt the Oral Microbiome?
Several lifestyle, dietary, and environmental factors can tip the oral microbiome out of balance.
Dietary Habits
High Sugar and Refined Carbohydrate Intake
Dietary sugars are fermented by bacteria such as Streptococcus mutans, producing acids that erode tooth enamel and promote tooth decay. A diet high in sugar also selects for acid-tolerant, disease-promoting bacteria, progressively undermining the diversity and balance of the oral microbiome.
Ultra-Processed Foods
Highly processed foods, low in fibre and rich in additives, reduce the substrate available to beneficial oral bacteria, mirroring the negative effects seen in the gut microbiome.
Low Fibre Intake
Fruits and vegetables provide not only vitamins and minerals but also polyphenols and antioxidants that actively support anti-inflammatory bacteria in the mouth. A diet rich in plant diversity is associated with a more balanced oral microbiome.
Smoking and Tobacco Use
Smoking significantly alters the oral microbial landscape, reducing microbial diversity and promoting the growth of pathogenic bacteria associated with periodontal (gum) disease. It also impairs the immune response in the gum tissue, allowing pathogens to take hold more easily.
Alcohol Consumption
Excessive alcohol consumption disrupts the oral microbiome by reducing saliva flow, creating a drier and more acidic environment that favours harmful microorganisms over beneficial ones.
Antibiotic Use
Broad-spectrum antibiotics are non-selective and can wipe out beneficial oral bacteria alongside targeted pathogens, leaving the mouth vulnerable to opportunistic organisms such as Candida albicans (oral thrush).
Poor Oral Hygiene Practices
Infrequent or inadequate brushing and flossing allows dental plaque (a biofilm of bacteria) to accumulate on tooth surfaces and below the gumline, creating an environment that strongly favours pathogenic species and leading progressively to gingivitis and periodontitis.
Stress and Chronic Illness
Chronic physiological stress alters salivary composition and immune function in the mouth, creating conditions more favourable to dysbiosis. Systemic illnesses such as diabetes, which impairs immune surveillance, are also closely linked to worsened oral microbiome balance.
Oral Microbiome Dysbiosis and Its Health Consequences
The consequences of an imbalanced oral microbiome extend well beyond the mouth. Pathogenic oral bacteria can enter the bloodstream (particularly through inflamed gum tissue) and travel throughout the body, triggering systemic inflammation and contributing to chronic disease.
Dental Caries (Tooth Decay)
Dental caries is one of the most prevalent diseases globally and is directly driven by oral dysbiosis. Acid-producing bacteria, particularly Streptococcus mutans, demineralise tooth enamel when their populations grow unchecked.
Gingivitis and Periodontitis
Gingivitis (inflammation of the gums) and periodontitis (advanced gum disease with bone loss) are the direct result of a dysbiotic oral microbiome. Bacteria such as Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola form what is known as the ‘red complex’, the key pathogenic drivers of periodontal disease. Untreated periodontitis creates a persistent source of systemic inflammation.
Cardiovascular Disease
The link between oral health and cardiovascular disease is one of the most robustly evidenced connections in the oral-systemic health literature. Periodontal pathogens (particularly P. gingivalis) have been found within arterial plaque. Research shows that these bacteria can enter the bloodstream via inflamed gum tissue, triggering chronic systemic inflammation that accelerates atherosclerosis (hardening of the arteries). Studies have also found oral bacterial DNA from streptococcal species in the thrombi of patients who have experienced acute ischaemic stroke.
Improving oral hygiene practices has been associated not only with reduced gingival inflammation, but also with measurable improvements in blood pressure and vascular endothelial function, reinforcing the direct cardiovascular relevance of oral health.
You can assess relevant inflammatory cardiovascular markers using the Cardiovascular Inflammation Test (CIT) – Finger Prick Blood Test and the Homocysteine Plasma Profile – Doctors Data Labs Blood Test.
Type 2 Diabetes
The relationship between the oral microbiome and diabetes is bidirectional. Elevated blood glucose levels impair immune function in the gum tissue, making individuals with diabetes more susceptible to periodontal disease. In turn, the chronic systemic inflammation driven by periodontal bacteria worsens insulin resistance and glycaemic control, creating a vicious cycle.
A 2024 systematic review found that daily toothbrushing and interdental cleaning (such as flossing) were associated with a reduced risk of developing type 2 diabetes in adults, underscoring how oral hygiene habits may have metabolic consequences.
Assessing markers linked to blood glucose regulation and nutrient status can provide valuable insight in this context. You could use the Diet & Lifestyle Blood Test Including Nurse Service or the Methylation Vitamin Blood Test to assess key markers including vitamin D, active B12, folate, magnesium, and blood glucose status. The effect of genetic variants on blood glucose regulation can also be assessed using The ULTIMATE Methylation Genetic Test – 78 Gene Markers.
Alzheimer’s Disease and Cognitive Decline
Emerging and increasingly compelling research connects the oral microbiome with brain health. Pathogenic bacteria from the mouth (particularly P. gingivalis and Treponema denticola) have been identified in the brains of individuals with Alzheimer’s disease. These bacteria appear to cross the blood-brain barrier and drive neuroinflammation, potentially triggering the accumulation of amyloid-beta plaques, a hallmark of Alzheimer’s pathology.
A 2025 study published in NPJ Dementia found that higher levels of pro-inflammatory anaerobic oral bacteria were associated with lower cognitive scores in older adults, while a healthier oral microbiome profile was linked to better cognitive performance.
Oral microbiome dysbiosis contributes to systemic inflammation that can impair the integrity of the blood-brain barrier, creating a pathway through which oral pathogens and their metabolites may access the brain over time.
For those with a family history of dementia or cardiovascular disease, or those experiencing early signs of cognitive decline, understanding your genetic risk profile is a meaningful step. The APOE DNA Test for Alzheimer’s Risk & Longevity examines your APOE gene variants (including the E4 allele associated with elevated Alzheimer’s risk_ alongside genes involved in methylation, inflammation, detoxification, and neuroprotection, providing a comprehensive and clinically actionable genetic picture.
Gut Health
The mouth is the beginning of the gastrointestinal tract, and an imbalanced oral microbiome has a direct impact on gut health. Harmful oral bacteria are continually swallowed (up to one litre of saliva per day) and in a dysbiotic state, these pathogens can colonise the gut, disrupting its microbial balance and contributing to conditions such as inflammatory bowel disease, leaky gut syndrome, and altered gut immunity.
If you are experiencing digestive symptoms alongside oral health concerns, assessing your gut microbiome alongside the oral microbiome can provide a more complete clinical picture. The GI360 Stool Test – Advanced Gut Microbiome & Digestive Health Analysis and Comprehensive Stool Analysis – Doctors Dataare valuable tools for this purpose.
Autoimmune Conditions
Chronic oral dysbiosis has been associated with a range of autoimmune diseases including rheumatoid arthritis and Sjögren’s syndrome. The persistent low-grade systemic inflammation driven by periodontal pathogens may act as a trigger for immune dysregulation in genetically predisposed individuals.
If you are experiencing symptoms such as unexplained fatigue, joint pain, skin rashes, or dry eyes and mouth that may suggest autoimmune activity, the Antinuclear Antibodies (ANA) Full Blood Test can help assess whether your immune system may be producing antibodies associated with conditions such as lupus, rheumatoid arthritis, or Sjögren’s syndrome.
Pregnancy Outcomes
Research consistently associates periodontal disease with adverse pregnancy outcomes, including preterm birth and low birth weight. The inflammatory mediators and bacterial products generated by oral infection appear capable of reaching the placenta and affecting foetal development. Oral health assessment and hygiene support should be a routine component of preconception and antenatal care.
Ways to Support a Healthy Oral Microbiome
Supporting a balanced oral microbiome requires a holistic approach that combines consistent oral hygiene with dietary and lifestyle considerations.
Oral Hygiene Practices
Brushing
Brush teeth at least twice daily, ideally after meals, using a soft-bristled toothbrush and a fluoride toothpaste. Brush for a minimum of two minutes, ensuring you cover all tooth surfaces and the gumline. We stock a range of microbiome-friendly toothpastes including the RiseWell Mineral Toothpaste (Hydroxyapatite), RiseWell PRO Mineral Toothpaste, and RiseWell Mineral Toothpaste (Flavourless), all formulated with hydroxyapatite (the mineral that makes up tooth enamel) to remineralise teeth without disrupting beneficial bacteria.
Flossing and Interdental Cleaning
Daily interdental cleaning (whether with floss, interdental brushes, or a water flosser) removes the biofilm that builds up between teeth where a toothbrush cannot reach. This is one of the single most impactful habits for reducing the bacterial load associated with periodontal disease. Our RiseWell Scrubby Floss is a braided, expandable floss infused with hydroxyapatite that cleans both between teeth and below the gumline.
Tongue Scraping
The tongue harbours a significant proportion of the mouth’s bacterial load. Using a tongue scraper daily can help to reduce the build-up of pathogens on the tongue surface and is a simple adjunct to standard brushing and flossing.
Mouthwash
Antiseptic mouthwashes can reduce harmful bacterial counts, but should be used judiciously as daily long-term use of alcohol-based mouthwashes may also disrupt beneficial bacteria and reduce the oral production of nitric oxide - which plays an important role in cardiovascular and blood pressure regulation. A 2024 systematic review found that antiseptic mouthwash use was associated with an 85% increased risk of hypertension and a 55% increased risk of diabetes. Alcohol-free, microbiome-conscious formulations are preferable for daily use. We stock the RiseWell Balancing Mouthwash, Dental Herb Tooth & Gums Tonic Oral Rinse, and Dental Herb Under the Gums Irrigant, all chosen with bacterial balance in mind.
Regular Dental Appointments
Professional cleaning (scaling and polishing) removes calcified plaque deposits (tartar) that cannot be removed by brushing at home. Regular dental check-ups also allow for early detection of periodontal disease and other oral conditions before they become more serious. Aim for at least two professional check-ups per year.
Dietary Support
Reduce Sugar and Refined Carbohydrates
Reducing your intake of dietary sugars and refined carbohydrates is one of the most direct ways to reduce the substrate available to acid-producing, cavity-causing bacteria. Be mindful of hidden sugars in drinks, sauces, and processed foods.
Eat a Diverse, Plant-Rich Diet
A diet rich in fruits, vegetables, legumes, and whole grains supports microbiome diversity throughout the gastrointestinal tract, including the mouth. Polyphenol-rich foods such as berries, green tea, olive oil, and dark leafy greens have demonstrated anti-inflammatory and antimicrobial properties that may directly support the oral microbiome.
Stay Well Hydrated
Adequate hydration supports healthy saliva production. Saliva is a critical component of oral defence, it contains antibacterial proteins, buffers acid, and helps remineralise enamel. Chronic dehydration or dry mouth (xerostomia) creates conditions that favour pathogenic bacteria.
Limit Alcohol
Reducing alcohol intake helps to preserve saliva flow and maintain a less acidic oral environment, both of which support a healthier microbial balance.
Lifestyle Factors
Quit Smoking
Smoking is one of the most destructive habits for the oral microbiome and is a major independent risk factor for periodontal disease and oral cancer. Stopping smoking allows for significant microbial recovery, alongside the many other well-evidenced health benefits.
Manage Stress
Chronic stress impairs immune function in the gum tissue and alters salivary composition, both of which promote dysbiosis. Mindfulness practices, regular physical activity, adequate sleep, and appropriate support for mental health can all help to reduce the physiological impact of chronic stress.
Optimise Sleep
Poor sleep quality is increasingly linked to systemic inflammation and immune dysregulation. Prioritising 7-9 hours of quality sleep per night supports immune function throughout the body, including in the oral cavity.
Nutritional Supplements That May Support Oral Microbiome Health
• Oral and dental probiotics: Strains such as Streptococcus salivarius K12 and M18 have been researched for their role in supporting a balanced oral microbiome. A 2025 meta-analysis concluded that probiotics show promise as adjunctive therapy for periodontal disease. Browse our probiotic range, including the UltraFlora Duo – Metagenics.
• Vitamin D: Vitamin D plays a significant role in immune regulation and supports periodontal health. Deficiency is associated with increased risk of gum disease. We stock the Vitamin D3/K2 Liquid – Amy Myers MD and Optimal Vitamin D3 + K2 Drops – Seeking Health. You can test your levels using the Vitamin D – Dried Blood Spot Test, or assess alongside broader markers with the Methylation Vitamin Blood Test or Diet & Lifestyle Blood Test.
• Vitamin C: Essential for collagen synthesis and gum tissue integrity. Deficiency is directly associated with gum fragility and bleeding. We stock Liposomal Vitamin C Liquid – Pure Encapsulations. Levels can be assessed as part of the Methylation Vitamin Blood Test.
• Magnesium: Magnesium plays an important role in immune function and inflammation regulation. We stock Magnesium Glycinate – Pure Encapsulations, Magnesium Citrate – Pure Encapsulations, and Magnesium L-Threonate (Neuro-Mag) – Life Extension (the only form of magnesium shown to cross the blood-brain barrier, supporting cognitive function alongside oral health). Levels can be checked using the Diet & Lifestyle Blood Test or Methylation Vitamin Blood Test.
• Coenzyme Q10 (CoQ10): Some evidence supports topical and systemic CoQ10 in reducing periodontal inflammation and supporting gum tissue health We stock LLQ1 Liposomal CoQ10, 240ml – Lipolife. And you can browse our Energy, Respiratory & Circulation supplement range which includes CoQ10 products.
• Zinc: Zinc has antimicrobial and anti-inflammatory properties in the oral cavity. We stock Zinc 30 – Pure Encapsulations and Zinc Bisglycinate – Thorne Research. Levels can be assessed as part of the Methylation Vitamin Blood Test.
• Omega-3 fatty acids: Anti-inflammatory omega-3s (EPA and DHA) have been associated with reduced severity of periodontal disease. We stock Life & Soul High Strength Omega-3 Fish Oil - Bare Biologyand you can browse our omega-3 and circulation supplement range. Your omega-3 and omega-6 status can be assessed using the Diet & Lifestyle Blood Test with Omega 3 & 6.
Assessing Your Oral Microbiome
For individuals with recurrent oral health issues, persistent bad breath, bleeding gums, digestive complaints, or inflammatory conditions, testing the oral microbiome can provide valuable insights into the specific bacterial imbalances at play and help guide a targeted intervention strategy.
The Oral Microbiome Health Test at My Body Fabulous uses advanced shotgun sequencing technology to evaluate the composition of bacteria, archaea, and fungi in a saliva sample. It identifies up to 700 microbial species, reporting on 25 key potential pathogens linked to plaque, cavities, gum disease, and systemic inflammation, as well as 16 opportunistic taxa. Because oral health is dependent on microbial balance rather than diversity alone, the test specifically assesses the ratio of beneficial commensal bacteria to pathogenic species, providing a nuanced and clinically useful picture of your oral environment.
The test is particularly valuable for assessing risk factors associated with dental caries, gingivitis, periodontitis, halitosis, and oral thrush, as well as for evaluating the oral microbiome’s potential contribution to cardiovascular health, systemic inflammation, and beyond.
Results are provided alongside a personalised written report from our clinical team covering dietary, lifestyle, and supplement recommendations tailored to your results, with the option of a follow-up video call to discuss your findings in detail.
In Summary
The oral microbiome is a critical and often underestimated pillar of overall health. Far from being an isolated system, what happens in the mouth has proven connections to the cardiovascular system, the brain, the gut, metabolic health, immunity, and reproductive health. Dysbiosis in the oral cavity (driven by poor diet, smoking, stress, and inadequate oral hygiene) creates a source of persistent systemic inflammation that can silently contribute to serious chronic disease over time.
The good news is that the oral microbiome responds well to targeted interventions. Consistent and thorough oral hygiene, a diverse and plant-rich diet, the reduction of key disruptors such as sugar and smoking, and appropriate microbiome-targeted supplementation can all support a healthier oral environment, with benefits that extend throughout the body.
If you would like to assess the current state of your oral microbiome, explore the Oral Microbiome Health Test or Book an Advice Call with our Clinical Team to discuss which testing approach is right for you.
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Dr. Diana Montalvo
Functional Medicine Doctor
Body Fabulous
References
1. Oral microbiome composition & 700+ species Rajasekaran JJ, Krishnamurthy HK, Bosco J, et al. "Oral Microbiome: A Review of Its Impact on Oral and Systemic Health." Microorganisms. 2024;12(9):1797. https://pmc.ncbi.nlm.nih.gov/articles/PMC11434369/
2. Second most diverse microbiome in the body Welch JLM, et al. / British Dental Journal overview: "The oral microbiome — an update for oral healthcare professionals." British Dental Journal. 2016. https://www.nature.com/articles/sj.bdj.2016.865
3. Oral dysbiosis and systemic disease (general) Tian J, et al. "Oral microbiome in human health and diseases." mLife. 2024. https://onlinelibrary.wiley.com/doi/full/10.1002/mlf2.12136
4. Oral microbiome & cardiovascular disease Frontiers in Cellular and Infection Microbiology. "Oral microbiota in cardiovascular health and disease." 2025. https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2025.1731845/full
5. Oral bacterial DNA found in stroke thrombi Institute for Functional Medicine. "Oral Microbiome: Connections to Cardiovascular Disease." https://www.ifm.org/articles/oral-microbiome-and-cardiometabolic
6. Oral hygiene improving vascular function & blood pressure Park et al., 2019 / Czesnikiewicz-Guzik et al., 2020 — cited within: Frontiers in Cellular and Infection Microbiology, 2025 (ref 4 above).
7. Oral bacteria found in arterial plaque Nature Scientific Reports. "Exploring the presence of oral bacteria in non-oral sites of patients with cardiovascular diseases using whole metagenomic data." 2024. https://www.nature.com/articles/s41598-023-50891-x
8. Oral microbiome & type 2 diabetes (bidirectional relationship) Rajasekaran et al., 2024 (ref 1 above); also: ScienceDirect. "Age-related oral microbiota dysbiosis and systemic diseases." 2025. https://www.sciencedirect.com/science/article/pii/S0882401025004425
9. Toothbrushing & flossing reducing risk of type 2 diabetes — 2024 systematic review Church L, Franks K, Medara N, et al. "Impact of Oral Hygiene Practices in Reducing Cardiometabolic Risk, Incidence, and Mortality: A Systematic Review." International Journal of Environmental Research and Public Health. 2024;21(10):1319. https://pmc.ncbi.nlm.nih.gov/articles/PMC11508105/
10. Oral microbiome & Alzheimer's / cognitive decline Engen PA, Green SJ, Barnes LL, Voigt RM, et al. "Oral microbiome brain axis and cognitive performance in older adults." npj Dementia. 2025;1:1. https://www.nature.com/articles/s44400-025-00004-4
11. P. gingivalis & Treponema denticola found in Alzheimer's brains PMC systematic review: "Association Between Oral Microbiota Dysbiosis and the Risk of Dementia: A Systematic Review." https://pmc.ncbi.nlm.nih.gov/articles/PMC12191743/
12. Oral microbiome, neuroinflammation & blood-brain barrier PMC: "Unlocking Modifiable Risk Factors for Alzheimer's Disease: Does the Oral Microbiome Hold Some of the Keys?" Journal of Alzheimer's Disease. 2023. https://pmc.ncbi.nlm.nih.gov/articles/PMC10200234/
13. Oral–gut microbiome axis & gut health Nature npj Biofilms and Microbiomes. "The oral-gut microbiota axis: a link in cardiometabolic diseases." 2025. https://www.nature.com/articles/s41522-025-00646-5
14. Oral dysbiosis & systemic inflammation / autoimmune disease PMC. "The Oral Microbiome and Systemic Health: Bridging the Gap Between Dentistry and Medicine." 2025. https://pmc.ncbi.nlm.nih.gov/articles/PMC11909285/
15. Oral infection & adverse pregnancy outcomes PMC. "The Oral Microbiome and Systemic Health: Bridging the Gap Between Dentistry and Medicine." 2025 (ref 14 above).
16. Streptococcus salivarius probiotics & gum health Institute for Functional Medicine. "The Oral Microbiome & Alzheimer's Disease Risk." https://www.ifm.org/articles/oral-microbiome-and-brain-health
17. Probiotics as adjunctive treatment for periodontal disease (2025 meta-analysis) Cited within IFM article above (ref 16).
18. UCSF — mouth as main entry point between outside world and body UCSF News. "How the Oral Microbiome is Connected to Overall Human Health." October 2024. https://www.ucsf.edu/news/2024/10/428681/how-oral-microbiome-connected-overall-human-health
