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May, 2024
June, 2024
Learn why you should start your probiotics journey with Bio-K+
Our scientifically proven formulas are designed to support your unique health journey
The oral microbiome is the second most complex microbiome in the human body. This guide covers mouth bacteria, the oral-gut axis, what disrupts oral microbial balance, and what science shows about oral microbiome probiotics.
After the gut, the oral cavity contains the second most complex microbiome in the human body. Approximately 700 bacterial species have been identified in the Human Oral Microbiome Database (HOMD), alongside fungi, viruses, archaea, and protozoa. Rajasekaran et al. (MDPI, 2024) characterize this ecosystem as highly dynamic, with functional roles in digestion, systemic immune signaling, and protection against pathogenic colonization.
Streptococcus species dominate the healthy oral microbiome, with S. salivarius, S. mutans, and S. sanguis among the most prevalent. The oral cavity is not uniform: the tongue dorsum, subgingival sulcus, tooth surfaces, and saliva harbor distinct bacterial communities. Periodontal pathogens including Porphyromonas gingivalis are present in most adults at low counts; dysbiosis occurs when these proliferate. Salivary bacterial density reaches an estimated 10⁸ to 10⁹ organisms per milliliter.
Adults swallow approximately 1.5 liters of saliva daily, carrying oral bacteria into the gut via the oral-gut axis. Ectopic oral bacteria have been identified in gut microbiomes of patients with gastrointestinal conditions. Peng et al. (Nature, 2022, cited 697) linked oral microbiome composition to cardiovascular disease, rheumatoid arthritis, and colorectal cancer. Porphyromonas gingivalis has been detected in brain tissue of Alzheimer's patients, suggesting systemic translocation via mucosal barrier crossing.
Dietary fermentable carbohydrates are metabolized by Streptococcus mutans into lactic acid, dropping plaque pH and favoring acid-tolerant pathogenic species over commensals. Broad-spectrum antibiotics are among the most potent oral microbiome disruptors, reducing commensal populations across both oral and gut environments simultaneously. Antibiotic-associated oral candidiasis results from Lactobacillus and Streptococcus population reduction. Maier et al. (2023) note recovery is variable by individual and antibiotic class.
Antiseptic mouthwashes containing chlorhexidine reduce oral bacterial load non-selectively, affecting commensal species alongside pathogens. Long-term implications for beneficial oral bacteria remain an area of active scientific discussion. Chronic stress elevates cortisol and reduces salivary immunoglobulin A, the primary mucosal antibody regulating oral microbial populations. Reduced saliva flow from stress or mouth breathing removes pH buffering, antimicrobial proteins, and mechanical clearance simultaneously.
Inchingolo et al. (2023) found probiotic microorganisms may have measurable effects in the oral environment. Beattie et al. (2024) found specific strains reduce oral pathogens and periodontal bacteria in clinical studies. Two mechanisms are under investigation: competitive exclusion and bacteriocin production. Luo et al. (Nature, 2024) observe that strain-level evidence does not transfer between gut and oral environments; oral-specific strains require alphanumeric-level identification to evaluate rigorously.
Bio-K+ applies the principles this page describes: strain-level identification, peer-reviewed evidence, and claims anchored to data. The three proprietary strains, Lacticaseibacillus casei LBC80R®, Lacticaseibacillus rhamnosus CLR2®, and Lactobacillus acidophilus CL1285®, carry full alphanumeric designations. They have been the subject of 16 published clinical trials across 45+ peer-reviewed publications over more than 30 years. Bio-K+ makes no oral health claims.
The oral microbiome is the community of microorganisms — bacteria, fungi, viruses, archaea, and protozoa — inhabiting the human mouth. Approximately 700 bacterial species have been identified in the Human Oral Microbiome Database (HOMD), making it the second most complex microbiome in the body after the gut. It includes both commensal species supporting oral health and opportunistic pathogens that proliferate when microbial balance shifts. The oral microbiome plays roles in digestion, immune function, and systemic health.
The dominant bacteria in a healthy oral microbiome belong to the genera Streptococcus, Veillonella, Fusobacterium, Prevotella, and Actinomyces. Streptococcus salivarius is one of the earliest colonizers of the oral cavity and remains a major commensal species in healthy adults. Periodontal pathogens like Porphyromonas gingivalis and Treponema denticola are present in low numbers in most adults; disease conditions occur when their populations expand. Different oral surfaces host distinct bacterial communities.
The oral-gut axis refers to the bidirectional relationship between the oral and gut microbiomes. Bacteria from the mouth are continuously swallowed in saliva and may colonize the gut, where ectopic oral bacteria have been identified in patients with gastrointestinal conditions. Conversely, gut microbiome composition influences salivary microbiome profiles. Peng et al. (Nature, 2022) documented links between oral pathogen translocation and systemic diseases including cardiovascular disease and colorectal cancer.
Broad-spectrum antibiotics reduce both pathogenic and commensal oral bacteria non-selectively. Diets high in fermentable carbohydrates lower plaque pH, favoring acid-tolerant pathogenic species. Antiseptic mouthwashes containing chlorhexidine are effective at reducing bacterial load but non-selective, affecting beneficial species alongside pathogens. Stress reduces salivary immunoglobulin A and saliva flow. Mouth breathing and xerostomia have similar drying effects. Recovery from disruption varies by individual and cause.
The most evidence-supported approaches include limiting fermentable carbohydrates, maintaining consistent mechanical oral hygiene, staying hydrated to support salivary flow, and managing stress. Targeted oral hygiene is preferable to broad-spectrum antiseptic mouthwashes for commensal bacteria preservation. Rajasekaran et al. (MDPI, 2024) identify diet modification as among the most evidence-supported oral microbiome interventions. Consult a dental or healthcare professional for guidance specific to your oral health situation.
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