Oral Microbiome
Synopsis
The Oral Microbiome: A Comprehensive Reference in Nutrition and Natural Health
1. Definition and Overview
The human oral cavity harbors a diverse and complex microbial community, collectively known as the oral microbiome. It encompasses diverse microorganisms, including bacteria, archaea, fungi, and viruses, and exists in the form of a biofilm that contributes significantly to maintaining oral homeostasis by fostering a harmonious balance within the oral environment.
With over 700 known bacterial species, the oral microbiome is the second most diverse microbiota within the human body. This vibrant ecosystem encompasses a wide range of bacterial phyla, including Actinobacteria, Bacteroidetes, Chlamydia, Euryarchaeota, Fusobacteria, Firmicutes, Proteobacteria, Spirochaetes, and Tenericutes.
The oral microbiome is a highly diverse community of microorganisms — bacteria, fungi, viruses, and archaea — living in different oral cavity niches. Several bacterial species have been identified from the oral cavity using high-throughput sequencing such as metagenomic shotgun sequencing and 16S rRNA sequencing. Oral microbiome composition is site-specific, with different microbial communities present at different sites such as teeth, gingival sulcus, tongue dorsum, inner cheeks, hard and soft palate, and tonsillar crypts.
At the time of birth, the oral cavity is microbe-free and is colonized by microbes within hours from the surrounding environment. It is, however, difficult to define the exact composition of the oral microbiome because the mouth has continuous exposure to exogenous bacteria in food, water, and air.
2. The Concept of Oral Dysbiosis
The dysbiotic state, in which the microbial composition is altered and the microecological balance between host and microorganisms is disturbed, can lead to oral and even systemic diseases. Dysbiosis of the oral microbiome can contribute to the development of numerous oral and systemic diseases, including dental caries, periodontitis, oral and other cancers, cardiovascular disease, and diabetes. It is associated with an increase in pathogenic bacteria and a corresponding decrease in beneficial bacteria.
Periodontitis may be considered akin to bacterial vaginosis or inflammatory bowel disease because it is not the singular absence or presence of a given species or subgenus that drives oral gum inflammation; rather, the complexity of the subgingival microbiota and biofilm establishment promote a model of a microbial community-associated disease.
Microbiomes associated with periodontal disease have a more diverse community structure that significantly resembles patterns seen among different patients. In healthy individuals, the microbiome's taxonomic diversity is low but composition varies to a greater extent among individuals. Taxonomic data analysis shows that the diseased microbiome undergoes a microbial community shift from being dominated by Gram-positive bacteria in health to Gram-negative bacteria in disease.
3. Body Systems Involved
Reviews have explored novel associations between the oral microbiome and systemic diseases including gastrointestinal, cardiovascular, endocrinal, and neurological conditions, autoimmune diseases, and cancer.
3.1 Cardiovascular System
Cardiovascular diseases remain the leading global cause of morbidity and mortality, with increasing evidence implicating oral microbiota dysbiosis as an independent and modifiable risk factor. Microbial balance disruptions are associated with oral pathologies like dental caries and periodontitis as well as systemic diseases such as cardiovascular diseases, adverse pregnancy outcomes, and respiratory diseases. Mechanistic pathways linking oral dysbiosis to systemic inflammation include endothelial dysfunction and immune modulation. Key microbial species drive systemic pathologies through hematogenous dissemination and inflammatory signaling.
3.2 Respiratory System
Oral dysbiosis increases the burden of pathogenic microbes that can colonize the respiratory tract and lungs, contributing to a range of respiratory diseases. Epidemiological studies highlight the role of oral flora in both acute and chronic pulmonary diseases. Poor oral health is associated with a heightened risk of respiratory illness.
3.3 Gastrointestinal System
Research pathways examine the interaction between the gut and oral microbiome — specifically, how oral microbiota impacts the composition of the gut microbiome, affecting immune responses and ultimately influencing metabolic and inflammatory disorders.
3.4 Neurological System and Mental Health
Systematic reviews have demonstrated consistent correlations between oral dysbiosis and depression, including reduced microbial diversity, elevated systemic cytokines (IL-1β, IL-6, TNF-α), and dysregulation of neurotrophic factors such as brain-derived neurotrophic factor (BDNF). This growing body of evidence suggests that oral health may be an often-overlooked but potentially modifiable factor associated with mental and cognitive well-being.
3.5 Endocrine System and Metabolic Health
Dysbiosis in the oral microbiota has been linked to conditions such as dental caries, periodontal diseases, and systemic disorders including diabetes, cardiovascular disease, obesity, rheumatoid arthritis, Alzheimer's disease, and colorectal cancer. Growing data indicate that oral dysbiosis may also contribute to inflammatory processes in obesity, promoting metainflammation within adipose tissue and aggravating metabolic dysfunction.
3.6 Immune System
The dynamic oral microbiota cooperates with the host to reflect the information and status of immunity and metabolism through two-way communication along the oral cavity and the systemic organs. The oral cavity is one of the most important interaction windows between the human body and the environment. Vitamin D, for example, is essential for calcium homeostasis, bone remodeling, and immune function, modulating both innate and adaptive immune responses, enhancing antimicrobial peptide production and reducing inflammatory cytokine expression.
4. Contributing and Associated Factors
4.1 Diet and Macronutrient Composition
Diet plays a central role in shaping the composition and metabolic activity of the oral microbiota, thereby influencing both oral and systemic health. Disturbances in this delicate host–microbe balance, triggered by dietary factors, smoking, poor oral hygiene, or antibiotic use, can lead to microbial dysbiosis and increase the risk of oral diseases such as periodontitis, as well as chronic systemic disorders including diabetes, cardiovascular disease, Alzheimer's disease, and certain cancers.
Diet plays an important role in the typical oral dysbiosis of periodontal disease, as it provides nutritional substrates for microorganisms, can promote the creation of a microenvironment suitable for the multiplication and survival of certain periodontal pathogen bacteria, and can inhibit the growth of other microorganisms.
Dental caries is attributed to high dietary intake of carbohydrates, leading to increased production of acid by microbes (which reduces the buffering capabilities of saliva), reductions in salivary pH, increased production of biofilm exopolysaccharide matrix (that entraps and concentrates acids on enamel surfaces), and induction of positive-feedback loops that encourage outgrowth of aciduric and acidogenic species, including S. mutans and Lactobacillus species.
Frequent sugar exposure tends to favor acidogenic/aciduric bacteria at the expense of others, indicating a diet-induced dysbiosis rather than a stable, balanced microbiome. Conversely, diets high in processed foods, added sugars, and saturated fats correlate with dysbiosis and an elevated risk of oral and gastrointestinal diseases.
4.2 Tobacco Use
Smoking and smokeless tobacco influence the oral microbial community composition, and there is a definitive shift in the abundance of oral taxa favoring an anaerobic environment, thus promoting a proinflammatory milieu. It is suggested that smoking may perturb the balance of the oral microbiome by affecting the relationships between bacteria and altering their metabolic pathways.
4.3 Alcohol Consumption
Diet, smoking, and alcohol consumption, as well as lifestyle choices and medical conditions, can affect the balance of the oral microbiome and lead to dysbiosis, which can result in oral health issues like dental caries, gingivitis, periodontitis, oral candidiasis, and halitosis.
4.4 Medications
The main factors influencing the composition of a microbiome that may cause dysbiosis include pharmaceuticals, specifically antibiotics, nutrition, as well as psychological and physical stress. The oral microbial composition can evolve rapidly in response to oral environmental changes. The triggers for change in the oral microbiome encompass alterations in pH, nutrition, and salivary fluid.
4.5 Systemic Diseases
The multitude of factors influencing the oral microbiome — from diet and smoking to systemic diseases like diabetes and host genetics — underscores that dysbiosis is not a simple infection but a complex ecological collapse.
4.6 Early Life and Developmental Factors
The oral microbiome is acquired as early as intrauterine life. Several studies have demonstrated the presence of microorganisms in the placenta, umbilical cord blood, amniotic fluid, and meconium.
4.7 Saliva and Oral Hygiene
Oral microbiome dysbiosis refers to an imbalance or disruption in the composition and functioning of the oral microbial community. Various factors such as poor oral hygiene, dietary habits, medical conditions, medications, and lifestyle choices can lead to this disturbance, which disrupts the harmonious interactions between different bacteria, altering the overall microbial ecology. The repercussions include dental caries, periodontal diseases, halitosis, and oral candidiasis.
5. Nutrients, Herbs, and Natural Ingredients
5.1 Probiotics
Scientific Evidence
Data from systematic reviews and meta-analyses show that probiotics positively impact clinical parameters of oral diseases such as gingivitis, dental caries, and periodontitis. However, the working mechanism of probiotics is not fully understood, but is hypothesized to be mediated by direct and indirect interactions with the oral microbiota and the human host.
Multiple RCTs have been performed studying the potential effect of probiotics on gingivitis, dental caries, and periodontitis as evaluated by microbial endpoints. In general, results are conflicting, with some studies reporting a positive effect, whereas others are not able to record any effect.
Most clinical trials reported a significant reduction in Streptococcus mutans levels following administration of probiotic strains, particularly Lactobacillus paracasei, Lactobacillus rhamnosus, and Bifidobacterium lactis. Several studies also demonstrated a decreased incidence of new carious lesions and an improvement in salivary immune markers.
A systematic review of 24 clinical trials including 1,612 participants found that individuals receiving probiotic products experienced a significant 65% reduction (p < 0.05) in the count of Streptococcus mutans in their mouths. Probiotic products were found to be more effective or equal in effect compared to chlorhexidine in reducing oral pathogens, gingival index, and plaque index scores.
An umbrella review of meta-analyses (literature searched up to October 2025) concluded that while evidence suggests probiotic supplementation can favorably impact oral microbial markers, halitosis parameters, and caries progression, the heterogeneity of interventions, reliance on surrogate endpoints, and limited long-term data mean that recommendations for routine clinical use must remain cautious. Future research should emphasize well-designed RCTs with standardized probiotic strains and dosing regimens.
Until large, strain-specific randomized trials report consistent effects on clinically meaningful outcomes, routine use of probiotics for oral disease prevention should be considered experimental.
5.2 Xylitol
Traditional and Nutritional Context
Xylitol is a naturally occurring five-carbon polyol sweetener known for its beneficial effects on oral health, particularly when consumed in the form of chewing gum.
Scientific Evidence
In a 2025 systematic review of clinical studies, in 12 out of 14 studies xylitol gum significantly decreased mutans streptococci (MS) counts compared with sorbitol gum. Plaque accumulation decreased in 6 out of 10 studies, and caries occurrence in 3 out of 5 trials when xylitol gum was compared with polyol control gum.
A systematic review of RCTs concluded that xylitol consumption is likely to decrease MS counts, but it may not change the overall microbiota. Xylitol shows properties of an oral prebiotic. However, some studies have found no effects of xylitol consumption on either salivary MS or lactobacilli, and a systematic review determined that evidence to support xylitol over sorbitol was contradictory.
Xylitol gum chewing is suggested to act as an adjunct to toothbrushing for reducing caries-associated MS and plaque accumulation to control and prevent caries occurrence in children and adults. Adults with other plaque-related diseases like periodontal disease should also benefit from xylitol gum.
5.3 Polyphenols: Green Tea (Camellia sinensis) and Cranberry (Vaccinium macrocarpon)
Traditional Use
The impact of diet on oral health is observable in populations that consume high quantities of polyphenol-rich foods or beverages; such populations have low caries incidence and better overall oral health. Camellia sinensis, the plant from which various forms of tea are derived, and Vaccinium macrocarpon (American cranberry fruit) have received notable attention both for their prevalence in the human diet as well as for their unique composition of polyphenols.
Scientific Evidence
Dietary polyphenols present in a wide variety of plant-based foods, herbs, and botanicals have been shown to exert antimicrobial, anti-inflammatory, and reduced osteoclast and alveolar bone loss activities in animal models of periodontitis. Polyphenol-containing beverages and foods, especially green tea and its active catechin epigallocatechin-3-gallate (EGCG), cranberries, pomegranates, and fruit and vegetable extracts have reported bacteriostatic/bactericidal activity against microbial species such as P. gingivalis and shown total bacterial burden reduction in clinical studies. These polyphenols also exhibit anti-inflammatory and antioxidant effects, which have the potential to impact various biological mechanisms for reducing the initiation and progression of periodontitis.
The biologically active constituents of these plants have demonstrated potent enzyme-inhibitory properties without being bactericidal, a key quality that is important in developing therapies that will not cause microorganisms to develop resistance.
Research on beverages rich in antimicrobial plant polyphenols indicates they reduce plaque adherence and may benefit oral health. Cranberry extract was also found to be bactericidal against periodontal pathogens including P. gingivalis, Fusobacterium nucleatum, and a multispecies anaerobic biofilm.
Limitation: Most polyphenol studies in the oral context are limited to laboratory (in vitro), animal models, or small human studies. Well-powered, long-term clinical trials in humans are limited, and results from existing studies should be interpreted cautiously.
5.4 Vitamin C (Ascorbic Acid)
Scientific Evidence
Vitamin C regulates numerous biochemical reactions, but foremost is involved in synthesizing collagen. Periodontitis is a common disorder affecting the bone and soft tissues of the periodontal complex; when untreated, it may lead to severe mobility or tooth loss. Vitamin C deficiency can lead to damage to the periodontal ligaments, and vitamin C supplementation has been shown to improve postoperative outcomes in patients with periodontitis.
In vitro studies have shown that vitamin C intake may play an important role in the prevention of gingivitis and periodontal inflammation. Vitamins A, C, D, and E, along with melatonin, have antioxidant effects that may slow the inflammatory onset of periodontitis.
5.5 Vitamin D
Scientific Evidence
Vitamin D is essential for calcium homeostasis, bone remodeling, and immune function. It modulates both innate and adaptive immune responses, enhancing antimicrobial peptide production and reducing inflammatory cytokine expression.
Evidence in the recent literature reinforces the importance of vitamin D for periodontal health. Periodontal disease appears to be correlated with low vitamin D serum levels; a cohort study of pregnant women assessed serum vitamin D levels alongside oral health indicators including Oral Hygiene Index, Plaque Control Record, Gingival Bleeding Index, and Community Periodontal Index of Treatment Needs.
5.6 Omega-3 Fatty Acids
Scientific Evidence
Omega-3 fatty acids reduce the production of pro-inflammatory mediators. A diet rich in omega-3, plant nitrates, and phytochemicals has been shown to protect against periodontitis. Polyunsaturated fats such as omega-3 have shown a positive effect on periodontium conditions.
Micronutrients including vitamin C, vitamin D, calcium, magnesium, and omega-3 fatty acids exert essential roles in tissue repair, collagen metabolism, bone turnover, innate immunity, and inflammatory resolution.
5.7 Oil Pulling (Kavala/Gandusha)
Traditional Use
In Ayurvedic texts such as the Charaka Samhita, oil pulling is mentioned as Kavala or Gandusha. Oil pulling has been used extensively as a traditional Indian folk remedy for many years to prevent decay, bleeding gums, oral malodor, dryness of the throat, cracked lips, and for strengthening teeth, gums, and jaws.
Scientific Evidence
A 2024 systematic review of 31 studies found that oil pulling with sesame or coconut oil showed moderate reductions in microbial load and improved gingival health, though findings varied compared to chlorhexidine mouthwash.
A pilot study using 16S rDNA next-generation sequencing found that oil pulling resulted in a significant and transient reduction of the overall microbial burden in comparison to saliva examined prior to and after pulling. Both oil and saline pulling samples mirrored the individual oral microbiomes in saliva. The authors concluded that oil pulling is able to reduce the overall microbial burden of the oral cavity transiently. These findings are limited by the very small sample sizes (three subjects) and the pilot nature of this study.
Broader evidence shows that oil pulling can reduce total oral bacterial counts and reduce plaque and gingival scores.
5.8 Neem (Azadirachta indica)
Traditional Use
Azadirachta indica, commonly known as the Neem tree, Indian lilac, or margosa tree, has been used as a traditional plant medicine in various diseases. The antibacterial action of neem is believed to be due to active phytochemical constituents like nimbidin, nimbolide, gedunin, and mahmoodin.
Scientific Evidence
A 2024 systematic review found that miswak (derived from the Salvadora persica tree) statistically significantly reduced plaque accumulation and gingival inflammation, performing comparably to or better than conventional toothbrushes. Herbal dentifrices and mouthwashes containing neem, clove, turmeric, and ginger exhibited antimicrobial properties and were as effective as fluoridated products in reducing plaque and gingival inflammation. The evidence base for neem specifically is predominantly composed of small-scale trials with moderate to high risk of bias.
5.9 Dietary Fiber and Prebiotics
Scientific Evidence
Research on dietary bioactive compounds illustrates dual effects on oral microbiome dynamics: promotion of eubiosis through competitive exclusion and production of protective factors (short-chain fatty acids, bacteriocins), or contribution to dysbiosis characterized by pathogenic biofilm formation and release of inflammatory mediators.
Various dietary components, such as fiber, prebiotics, probiotics, and bioactive compounds, have demonstrated significant effects on the diversity and function of microorganisms in oral ecosystems. For dietary components to be defined as true oral prebiotics, their action needs to be demonstrated in in vivo studies, taking into account even more complex interbacterial interactions and fluctuations in environmental factors.
6. Dietary and Lifestyle Factors
6.1 The Mediterranean Diet
The Mediterranean Diet (MD) model, comprising both healthy dietary choices and lifestyle, is linked to the prevention of several metabolic and chronic-degenerative pathological processes, including oral diseases. The MD is a plant-based diet, enriched in anti-inflammatory and antioxidant nutrients, which may induce beneficial effects against dental caries and periodontal diseases.
Dysbiotic oral microbiota has been associated with numerous systemic pathologies, including metabolic and neurodegenerative disorders. Some studies have highlighted that a diet rich in polyphenols, such as the MD, can positively modulate the oral microbiome, reducing the proliferation of pathogenic bacteria involved in periodontitis and neuroinflammation. This suggests that the beneficial effect of the MD may extend beyond gut microbiota, positively influencing oral health and reducing the risk of systemic diseases related to oral microbiota dysbiosis.
Anti-inflammatory dietary patterns, including the Mediterranean diet, demonstrate protective effects on oral microbiome composition.
6.2 Dietary Patterns and Evidence Limitations
Available evidence supports a biologically plausible, predominantly indirect diet–microbiome pathway, in which systemic metabolic and inflammatory states act as major effectors of oral dysbiosis and periodontal destruction. Direct dietary modulation of the oral microbiome shows promising protective signals but lacks conclusive long-term and human interventional validation. Thus, diet may function less as a driver of de novo microbial expansion and more as a strategy to preserve ecological stability, enhance resilience, and mitigate inflammatory burden locally and systemically.
6.3 A Whole-Diet Approach to Micronutrients
Diet is a key determinant of oral and periodontal health, influencing inflammation, oxidative stress, salivary composition, and the oral microbiome. Nutrient-dense and anti-inflammatory dietary patterns, such as the Mediterranean diet, plant-forward diets, and whole-food frameworks, support a more balanced host immune response, enhance microbial eubiosis, and improve clinical periodontal parameters.
One randomized clinical trial in which subjects were placed on a diet low in carbohydrates and rich in fibers and vitamins C and D showed notable improvements; oral parameters such as plaque index, bleeding on probing, and pocket depth were cut in half.
Deficiencies in essential nutrients can exacerbate periodontal tissue damage by impairing immune responses, promoting oxidative stress, and reducing bone and tissue regeneration.
6.4 Heavy Metal Exposure
Among dietary contaminants, exposure to toxic heavy metals such as cadmium, lead, mercury, nickel, and arsenic represents an underrecognized modifier of the oral microbial ecosystem. Even at low concentrations, these elements can disrupt microbial diversity, promote inflammation, and impair metabolic homeostasis.
6.5 Smoking and Tobacco Products
Cigarette smoke has been shown to increase the expression of and alter the functional activation of toll-like receptors including TLR-2 and TLR-4. Taxa enriched in smokers including Fusobacteria, Veillonella, Prevotella, and Actinomyces also bind to TLR-2 and TLR-4, and this signaling leads to upregulation of several proinflammatory pathways. TLRs and their signaling machinery have been subsequently implicated in a wide range of human diseases, including several oral cancers.
6.6 Oral Hygiene Practices
When poor oral hygiene persists, oral microorganisms may enter the bloodstream and disseminate to distant body sites. This bacterial translocation is of particular concern for systemic health, as it can initiate or accelerate the progression of several diseases.
6.7 Stress
Periodontal inflammation and dysbiosis of microbiota are not only caused by the lack of oral hygiene but also by environmental components, for example, poor diet and psychological stress.
7. Systemic Disease Associations: Summary of Evidence Strength
Left untreated or ineffectively treated, periodontitis is a known independent predictor of, and comorbid contributor to, preterm birth, cardiovascular disease, pulmonary disorders, diabetes, and obesity.
Oral dysbiosis is an important regulator of systemic disease processes and a promising target for diagnosis, prevention, and therapy. Integrating oral health and oral microbiome assessment into broader disease management may improve outcomes. However, methodological standardization and stronger causal evidence are still needed.
Emerging evidence indicates that disturbances in oral microbial communities — including genetic and functional diversity within species — are associated not only with oral diseases but may also contribute to the development and progression of systemic diseases. Much of the evidence linking the oral microbiome to systemic conditions remains associative in nature; while mechanistic plausibility is well-established, demonstrating causation requires larger, longitudinal human interventional trials that are still limited in number.
References
- Oral Microbiome: A Review of Its Impact on Oral and Systemic Health — PMC/MDPI Microorganisms (2024)
- The Oral Microbiome and Systemic Health: Bridging the Gap Between Dentistry and Medicine — PMC (2025)
- Oral microbiome and health — AIMS Microbiology / PMC (2018)
- The Oral Microbiota: Community Composition, Influencing Factors, Pathogenesis, and Interventions — Frontiers in Microbiology (2022)
- The Oral Microbiota: Community Composition, Influencing Factors, Pathogenesis, and Interventions — PMC (2022)
- Oral microbiota in human systematic diseases — PMC (2022)
- The Oral Microbiome and Systemic Health: Current Insights into the Mouth–Body Connection — MDPI Life (2026)
- The oral microbiome as a regulatory hub for systemic health: a systematic review — Journal of Oral Microbiology (2026)
- Diet–Oral Microbiota Interactions and Salivary Biomarkers of Nutritional Health: A Narrative Review — Nutrients (2026)
- A Cross-Talk between Diet and the Oral Microbiome: Balance of Nutrition on Inflammation and Immune System's Response during Periodontitis — PMC (2022)
- Oral Microbiome in Health and Disease: Maintaining a Healthy, Balanced Ecosystem and Reversing Dysbiosis — PMC (2023)
- Effect of Probiotic Supplements on the Oral Microbiota—A Narrative Review — PMC (2024)
- The role of probiotics in preventing dental caries: a systematic review of clinical evidence — Frontiers in Oral Health (2025)
- The effects of probiotics intervention on oral health outcomes: a comprehensive umbrella review of meta-analyses — Frontiers in Oral Health (2026)
- Clinical Efficacy of Probiotics on Oral Health: A Systematic Review of Clinical Trials — PubMed/Current Pharmaceutical Biotechnology (2023)
- Antimicrobial Traits of Tea- and Cranberry-Derived Polyphenols against Streptococcus mutans — PMC/Caries Research (2011)
- Dietary Polyphenols and Periodontitis—A Mini-Review of Literature — PMC (2018)
- Specific effects of xylitol chewing gum on mutans streptococci levels, plaque accumulation and caries occurrence: a systematic review — BMC Oral Health (2025)
- Effects of xylitol and erythritol consumption on mutans streptococci and the oral microbiota: a systematic review — Acta Odontologica Scandinavica (2020)
- Xylitol and sorbitol effects on the microbiome of saliva and plaque — PMC (2018)
- The Role of Vitamin C and Vitamin D in the Pathogenesis and Therapy of Periodontitis—Narrative Review — PMC (2023)
- Effects of Vitamin D, Melatonin, and Omega-3 Fatty Acids on Periodontal Health: A Narrative Review — PMC (2025)
- Nutritional Modulation of Periodontal Diseases: A Narrative Review of Recent Evidence — PMC (2024)
- The Impact of Nutritional Components on Periodontal Health: A Literature Review — Nutrients (2024)
- From Diet to Oral and Periodontal Health: Exploring the Crucial Role of Nutrition—A Narrative Review — PMC (2026)
- High-resolution taxonomic examination of the oral microbiome after oil pulling: a pilot study — PMC (2021)
- Traditional Oral Hygiene Practices and Their Effectiveness: A Systematic Review — PMC (2025)
- Effectiveness of Oil Pulling for Improving Oral Health: A Meta-Analysis — MDPI Healthcare (2022)
- Mediterranean diet: a potential player in the link between oral microbiome and oral diseases — PMC (2024)
- Effect of different forms of tobacco on the oral microbiome in healthy adults: a systematic review — PMC (2024)
- The oral microbiome: Role of key organisms and complex networks in oral health and disease — PMC (2021)
- Traditional Foods, Oral Microbiome, and Systemic Health: Molecular Pathways Linking Nutrition and Oral Disease Prevention — MDPI IJMS (2026)
- Diet type and the oral microbiome — Frontiers in Nutrition (2026)
- Editorial: Cross-kingdom interactions in oral dysbiosis and host response — PMC (2025)
- Oral-systemic connection: A narrative review of the role of oral health in the prevention and management of systemic diseases — Journal of Dentistry and Allied Sciences (2025)
Natural Remedies
Ingredients
- acaciaScientific
Acacia gum disrupts quorum sensing in key oral pathogens and promotes a balanced oral microbiome. Research published in Frontiers in Oral Health (2024) specifically identifies GA as an anti-biofilm agent that interferes with AI-2 signaling pathways used by periodontitis-associated bacteria, reducing their virulence and shifting microbiome composition toward a healthier balance.
- aloe veraScientific
Aloe vera mouthwash has been evaluated in multiple RCTs for its ability to reduce periodontal pathogens and modulate the oral microbial environment. It demonstrates antibacterial activity against Streptococcus mutans, E. faecalis, and periodontal pathogens, and antifungal activity against oral Candida. In a 30-day RCT (270 patients), aloe vera mouthwash reduced plaque and gingival inflammation comparably to chlorhexidine.
- betelScientific
Piper betle extracts demonstrate broad-spectrum inhibition of oral bacteria and fungi that constitute the oral microbiome, including Streptococcus mutans, Porphyromonas gingivalis, Staphylococcus aureus, and Candida albicans. Saliva obtained after chewing betel leaf reduced oral microflora by ~56%. Multiple in vitro and one clinical study support these effects.
- bifidobacterium animalisScientific
Bifidobacterium animalis (subspecies lactis, including strains BB-12 and HN019) has been directly studied for oral microbiome modulation and periodontal applications. Studies using metagenomic sequencing in rat periodontitis models showed significant alterations in subgingival microbiome composition. Clinical trials involving B. animalis subsp. lactis as an adjunct to periodontal therapy showed improvements in gingival inflammation.
- bifidobacterium bifidumScientific
Bifidobacterium bifidum has been studied within the genus context for oral microbiome modulation. The Bifidobacterium genus broadly inhibits periodontopathogens and cariogenic bacteria. B. bifidum is included in formulations studied for oral health and has in vitro evidence for inhibiting S. mutans and oral candida.
- bifidobacterium lactisScientific
Bifidobacterium lactis (including strains BB-12 and HN019) has been studied in multiple RCTs and in vitro for effects on the oral microbiome and periodontal health. BB-12 combined with L. rhamnosus GG altered oral microbiota in a 4-week RCT. B. lactis HN019 showed antimicrobial activity against P. gingivalis, P. intermedia, F. nucleatum, and A. actinomycetemcomitans in vitro and improved gingival inflammation in periodontitis patients.
- bifidobacterium longumScientific
Bifidobacterium longum has been included in oral probiotic formulations and evaluated for its ability to inhibit oral pathogens. In vitro studies demonstrate antimicrobial activity against S. mutans and periodontal pathogens. It is part of the broader evidence base for Bifidobacterium species modulating oral microbial ecology.
- black teaScientific
Black tea polyphenols selectively inhibit cariogenic and periodontopathogenic bacteria in the oral cavity while demonstrating prebiotic-like modulation of overall oral microbial ecology. In vitro evidence shows inhibition of Streptococcus mutans, Porphyromonas gingivalis, and other pathogens. Clinical oral microbiome intervention trials are limited.
- caprylic acidScientific
Huang et al. (2011, Archives of Oral Biology) demonstrated that short and medium-chain fatty acids, including caprylic acid, exhibit antimicrobial activity against oral microorganisms including Candida and cariogenic bacteria. Caprylic acid shows anticandidal activity in vitro with MIC values relevant to oral concentrations. Clinical oral use evidence remains primarily in vitro and traditional.
- cardamomScientific
In vitro studies demonstrate that cardamom extracts and essential oil inhibit multiple oral pathogenic organisms, including Streptococcus mutans, Candida albicans, and other Candida species, modulating the oral microbial ecology. A cardamom-based mouthwash (Denteez) inhibited 98.2% of clinical Candida isolates in vitro. Cineole, the primary oil component, is a potent antiseptic against oral bacteria.
- catechinsScientific
Catechins selectively inhibit periodontal and halitosis-associated pathogens (P. gingivalis, Prevotella, Fusobacterium, S. moorei) while sparing some commensal organisms, thereby shifting the oral microbiome toward a healthier composition. Both in vitro and clinical data support this antimicrobial rebalancing effect.
- cinnamonScientific
Cinnamon EO and cinnamaldehyde demonstrate broad-spectrum activity against oral microbiome pathogens including S. mutans, P. gingivalis, Prevotella intermedia, and Candida albicans, modulating the balance between commensal and pathogenic oral flora. A comprehensive PMC review confirmed significant antimicrobial activity against major cariogenic and periodontal pathogens.
- cloveScientific
Clove essential oil and eugenol exhibit well-documented antibacterial activity against key oral pathogens including Streptococcus mutans and periodontal bacteria. Eugenol is an FDA-approved dental antiseptic, and clove-based mouth preparations are used clinically.
- coconutScientific
A 2025 triple-blind RCT used 16S rRNA sequencing to show coconut oil pulling significantly shifted the oral microbiome in periodontitis patients, reducing pathogenic bacteria (Spirochaetaceae, Tannerellaceae) and increasing beneficial Streptococcaceae, with effects comparable to chlorhexidine.
- coconut oilScientific
Coconut oil oil pulling has been studied using 16S rRNA sequencing and shown to significantly shift the composition of oral microbiota in periodontitis patients, reducing known periodontal pathogens. RCTs confirm reductions in salivary Streptococcus mutans and total bacterial colony counts with daily coconut oil pulling.
- commiphoraScientific
Multiple in vitro and clinical studies confirm Commiphora myrrh modulates the oral microbiome by suppressing key pathogenic organisms such as Streptococcus mutans, Fusobacterium nucleatum, and Enterococcus faecalis. Studies have been conducted at clinical scale.
- cranberryScientific
Cranberry proanthocyanidins (PACs), particularly A-type oligomers, are well-studied for their anti-adhesion and antimicrobial effects against S. mutans and other cariogenic oral bacteria. A systematic review (BMC Oral Health 2024) confirmed cranberry and grape seed flavonoids effectively reduce S. mutans virulence factors. In vivo rat studies showed cranberry PAC treatment significantly reduced caries incidence and severity.
- EGCG (epigallocatechin gallate)Scientific
EGCG, the primary catechin in green tea, has demonstrated broad-spectrum antimicrobial activity against oral disease-associated microbes including S. mutans, P. gingivalis, A. actinomycetemcomitans, and Solobacterium moorei (halitosis). Multiple in vitro studies confirm inhibition of biofilm formation and virulence factors. Human studies of green tea consumption show measurable shifts in oral microbiota taxa.
- green teaScientific
Green tea and its catechins (especially EGCG) have demonstrated direct effects on oral microbiota, reducing cariogenic and periodontopathic bacteria while promoting shifts toward healthier microbial communities. Human studies show measurable oral microbiome changes after 2–4 weeks of consumption. Green tea inhibits S. mutans, P. gingivalis, and halitosis-causing bacteria.
- honeyScientific
Honey, particularly manuka, inhibits key oral pathogens including Streptococcus mutans, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans, and has been shown to reduce plaque indices in clinical studies. Its bactericidal activity against oral pathogens is well characterized in vitro, and clinical trials in periodontal patients demonstrate microbiome-modulating effects.
- lactobacillus acidophilusScientific
Lactobacillus acidophilus has been studied in combination oral probiotic trials for its effects on oral microbiome and periodontal/halitosis parameters. A 90-day double-blind RCT combining L. reuteri, L. salivarius, and L. acidophilus showed significant reductions in periodontal parameters and halitosis markers in 60 patients with severe periodontitis.
- lactobacillus brevisScientific
Lactobacillus brevis has been studied specifically for oral microbiome modulation. Clinical evidence shows that L. brevis lozenges significantly delayed the onset of gingival inflammation in healthy individuals who refrained from oral hygiene. Research cited in PMC sources confirms its role in reducing periodontal pocket depth and improving clinical attachment levels.
- lactobacillus caseiScientific
Lactobacillus casei has been studied for oral microbiome effects including inhibition of S. mutans and reduction of caries risk in children. It is included in critical appraisals of oral probiotics and has in vitro and clinical evidence supporting oral health benefits.
- lactobacillus fermentumScientific
Lactobacillus fermentum has been evaluated in oral microbiome contexts and is documented in critical appraisals of probiotics for oral health. It is one of the Lactobacillus species identified as capable of modulating oral microbial composition and reducing cariogenic bacteria.
- lactobacillus paracaseiScientific
Lactobacillus paracasei has been evaluated in oral health contexts, with strain SD1 shown to reduce S. mutans and progression of dental caries. Metagenomic analyses in experimental periodontitis models showed that L. paracasei L9 significantly altered subgingival microbiome composition and reduced pathogenic bacterial genera.
- lactobacillus plantarumScientific
Lactobacillus plantarum has demonstrated inhibition of key periodontal pathogens including Porphyromonas gingivalis in vitro and in clinical studies. A 2024 systematic review found evidence for clinical improvement in periodontal outcomes and caries risk reduction. Heat-killed L. plantarum L-137 has also been shown in clinical findings to inhibit periodontal pocket deepening.
- lactobacillus reuteriScientific
Lactobacillus reuteri (strains DSM 17938 and ATCC PTA 5289) is among the most studied oral probiotics, with multiple RCTs documenting reductions in periodontal pathogens, plaque, and gingival inflammation. It produces reuterin, which inhibits anaerobes responsible for gum disease and halitosis. A 12-week pyrosequencing RCT confirmed measurable shifts in oral biofilm composition.
- lactobacillus rhamnosusScientific
Lactobacillus rhamnosus GG and other strains have been assessed in multiple RCTs for effects on the oral microbiome, including salivary mutans streptococci levels, plaque, and gingival inflammation. A 4-week RCT combining LGG and Bifidobacterium lactis BB-12 demonstrated measurable changes in oral microbiota composition in healthy adults. Clinical evidence suggests benefit for gingivitis reduction.
- lactobacillus salivariusScientific
Lactobacillus salivarius has been studied for its ability to suppress Streptococcus mutans and periodontal pathogens. Strain WB21 was shown in a double-blind RCT to improve periodontal condition scores. A 90-day RCT using a combination including L. salivarius showed significant reductions in halitosis and periodontal parameters.
- lactococcus lactisScientific
Lactococcus lactis is a lactic acid bacterium that produces nisin and other bacteriocins documented for activity against oral pathogens including S. mutans and periodontal bacteria. It has been identified in research on oral microbiome modulation and is referenced in scientific literature on oral microbial ecology.
- lactoferrinScientific
Lactoferrin is an endogenous component of saliva and plays an established role in modulating the oral microbiome by selectively inhibiting pathogenic organisms while supporting commensal balance. It demonstrates antibiofilm activity against major oral pathogens and reduces iron availability for dysbiotic bacteria.
- lactoperoxidaseScientific
Clinical studies show LPO-system-containing oral hygiene products selectively modulate the oral microbiome, promoting health-associated bacteria while reducing periodontal pathogens. A randomized clinical study (Adams et al. 2017, Sci Rep) found an LPO-enzyme toothpaste caused significant shifts in plaque microbiome ecology. LPO-based lozenges were shown to reduce cariogenic bacteria without disturbing total commensal counts.
- magnoliaScientific
Magnolia bark extract selectively inhibits pathogenic oral bacteria—including Streptococcus mutans, Porphyromonas gingivalis, and Fusobacterium nucleatum—without eliminating the entire microbiome, supporting a more balanced oral microbiome. A randomized single-blind placebo-controlled trial showed MBE mouthwash significantly reduced S. mutans in dental plaque versus placebo.
- mastic gumScientific
Clinical studies show chewing mastic gum significantly reduces total viable bacteria and specifically lowers Streptococcus mutans and Lactobacilli counts in saliva of orthodontic patients. A 2023 systematic review of 14 studies confirmed inhibition of plaque-associated bacteria. Mastic outperformed both hydrogen peroxide and chlorhexidine in inhibiting periodontal pathogens without cytotoxicity to oral epithelial cells.
- melaleuca alternifoliaScientific
Controlled clinical studies show that 0.2% TTO mouthwash reduces mutans streptococci counts and total oral bacteria, with effects maintained for 2 weeks post-treatment. In vitro data confirms susceptibility of 161 oral bacterial isolates across 15 genera to TTO. A 2025 RCT found 0.2% TTO mouthwash provided antiplaque benefits comparable to chlorhexidine with fewer side effects.
- mintScientific
Mint oil beadlets have been tested in a pilot human study, showing measurable shifts in oral microbiome composition, reducing abundance of several genera associated with dental disease and halitosis. Peppermint oil's antibacterial spectrum covers multiple key oral pathogens across both in vitro and limited clinical research.
- monolaurinScientific
GML-containing mouthwashes have been studied in human and in vitro oral infection contexts, showing potent activity against oral H. pylori — a key pathogen in oral dysbiosis. Monolaurin reduces H. pylori biofilm, adhesion, and inflammatory cytokine expression in oral epithelial cells, suggesting selective antimicrobial remodeling of the oral microbiome.
- myrobalanScientific
TC extracts exert selective antibacterial activity against key oral pathogens including Streptococcus mutans, H. pylori, and Candida albicans, while clinical mouthwash trials confirm plaque microbiome disruption comparable to chlorhexidine without the latter's side-effect profile.
- myrrhScientific
Myrrh mouthwash has been evaluated in randomized controlled trials for dental plaque and gingivitis control. A 1% myrrh mouthwash reduced plaque accumulation significantly in a double-blind RCT, and myrrh mouthwash improved wound healing after tooth extraction in a separate RCT. Myrrh extracts show in vitro activity against key periodontal pathogens including Porphyromonas gingivalis.
- neem treeScientific
Multiple randomised clinical trials have compared neem-based mouthwashes and chips to chlorhexidine for plaque, gingivitis, and periodontitis, consistently showing clinically meaningful reductions in oral bacterial load. Active compounds nimbidin, azadirachtin, and nimbinin target both aerobic and anaerobic oral pathogens. Neem-based local drug delivery chips have also been trialled as adjuncts to periodontal therapy.
- oreganoScientific
Oregano oil has well-characterized antimicrobial and anti-biofilm activity against the full spectrum of major oral microbial pathogens, including S. mutans, S. aureus, Enterococcus faecalis, and Candida albicans. IADR research confirmed >99.99% killing of all oral pathogens tested, with potency equivalent to Listerine Naturals™. OEO disrupts oral biofilm architecture, which is foundational to oral microbiome modulation.
- peppermintScientific
A 2024 pilot human study (PMC11356387) found that a mint essential oil blend including peppermint, used twice daily for 7 days, significantly reduced periodontal and caries-associated bacteria (Actinomyces, Bacteroides, Fusobacterium, Porphyromonas, Prevotella, Streptococcus mutans) in the oral microbiome. Peppermint EO's antimicrobial effects on the oral microbiome have been observed across toothpaste, mouthwash, and beadlet delivery formats.
- pomegranateScientific
Pomegranate peel and juice extracts exhibit significant antimicrobial activity against key oral pathogens including Streptococcus mutans, Porphyromonas gingivalis, and Candida albicans. Several clinical studies have evaluated pomegranate-based mouthwashes, finding reductions in plaque, gingivitis, and pathogenic oral bacteria comparable to chlorhexidine.
- propolisScientific
Bee propolis contains antimicrobial flavonoids (galangin, pinocembrin) and phenolic acids (caffeic acid, ferulic acid) with documented activity against oral microbiome pathogens including S. mutans, E. faecalis, and oral Candida. In vitro studies confirm inhibition of cariogenic and periodontopathic species. A clinical toothpaste RCT combining propolis and tea tree oil demonstrated stabilization of oral bacterial microflora.
- red rootScientific
In vitro research directly demonstrates that Ceanothus americanus extracts selectively inhibit key pathogenic oral bacteria — including Streptococcus mutans, Porphyromonas gingivalis, and Prevotella intermedia — without being characterized for effects on beneficial commensal organisms. This provides a direct scientific basis for a relationship with the oral microbial environment. No human studies assessing oral microbiome composition have been conducted.
- sageScientific
In vitro and clinical studies confirm that S. officinalis extracts inhibit key oral pathogens including Porphyromonas gingivalis, Streptococcus mutans, and Candida species. A split-mouth RCT found sage gel as an adjunct to scaling improved gingival inflammation markers. Multiple clinical studies support its use in gingivitis and oral infections.
- sesameScientific
Sesame oil oil-pulling reduces populations of oral bacteria, including Streptococcus mutans, that form dental biofilm and contribute to plaque and dysbiosis. Clinical studies show significant reductions in bacterial load with regular sesame oil pulling. The mechanical swishing action combined with fatty acid antimicrobial properties disrupts microbial biofilm architecture.
- steviaScientific
Stevia extracts inhibit biofilm formation by Streptococcus mutans and Streptococcus gordonii, downregulate glucosyltransferase (Gtf) genes essential for exopolysaccharide synthesis, and reduce cariogenic bacteria counts. A clinical comparison found 0.5% aqueous stevia leaf extract comparable to 0.12% chlorhexidine mouthwash in reducing S. mutans and Lactobacillus counts in high-caries-risk patients.
- steviol glycosidesScientific
Steviol glycosides are non-fermentable by cariogenic oral bacteria such as Streptococcus mutans, conferring noncariogenic properties. Preclinical and in vitro studies demonstrate that SGs suppress S. mutans acid production and growth, and in silico analysis suggests SGs bind the S. mutans glucan-binding protein more effectively than eugenol.
- streptococcus salivariusScientific
Streptococcus salivarius is a dominant commensal of the healthy oral microbiome and is administered as a probiotic (strains K12 and M18) to modulate oral microbial balance. Clinical RCTs show K12 reduces halitosis-causing bacteria via bacteriocin-like inhibitory substances, while M18 improves periodontal parameters. A 2026 RCT of 55 periodontitis patients using M18 lozenges for 12 weeks demonstrated significantly improved pocket probing depth, bleeding on probing, and plaque index versus placebo.
- sunflower oilScientific
A pilot clinical study using 16S rDNA next-generation sequencing showed that oil pulling with standardized sunflower seed oil transiently and significantly reduced the overall microbial burden of the oral cavity. The oil/saliva emulsion captured bacteria representative of the entire oral microbiome. Evidence is preliminary due to small sample size.
- tea tree oilScientific
Tea tree oil (Melaleuca alternifolia) has documented antimicrobial activity against oral pathogens including S. mutans, P. gingivalis, and oral Candida. Combined with propolis in a clinical toothpaste RCT (n=51 patients), it stabilized oral bacterial microflora compared to controls. Multiple studies confirm its role in oral microbiome modulation.
- terminaliaScientific
T. chebula extracts have been shown in clinical and laboratory studies to modulate the oral microbiome by reducing cariogenic and periodontal pathogens. A clinical study found aqueous T. chebula rinse reduced salivary S. mutans counts and raised salivary pH. Triphala mouthwash (containing T. chebula) produced significant reductions in oral streptococcal counts in human subjects.
- thymeScientific
Thymol selectively inhibits oral pathogens including Streptococcus mutans, periodontopathogens (P. gingivalis, T. forsythia), and Candida species while disrupting biofilm architecture. This modulates the oral microbiome composition demonstrated in clinical periodontal trials. Thymol is a key ingredient in commercially established oral care products with documented microbiome-modulating effects.
- triphalaScientific
Multiple human RCTs demonstrate Triphala mouthwash significantly reduces Streptococcus mutans, Streptococcus sanguinis, Lactobacillus, and total aerobic colony counts in the oral cavity. A 90-day RCT in schoolchildren confirmed significant microbial reduction comparable to chlorhexidine. Its broad-spectrum antimicrobial activity is well-characterized.
- wasabiScientific
Wasabi isothiocyanates, including allyl isothiocyanate, exhibit broad-spectrum antibacterial activity against food-borne and oral pathogens. Isothiocyanates are reported to inhibit microbial adhesion and proliferation, reducing dental plaque bacteria. Wasabi has been used traditionally in Japan as an antimicrobial food pairing, underpinning its potential to modulate the oral microbiome.
- goldensealTraditional
Goldenseal's broad antimicrobial activity against oral bacteria provides a rationale for its traditional use in oral hygiene and influence on the oral microbiome. In vitro evidence for berberine's activity against oral pathogens is documented, though human clinical microbiome trials are lacking.