Probiotic supplementation may improve salivary buffering and reduce cariogenic bacteria

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Frontiers in Medicine Published June 7, 2026 Medically reviewed June 7, 2026 DOI ↗ By Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

Key Takeaway

Interpret probiotic evidence cautiously due to heterogeneity and lack of meta-analysis.

This systematic review synthesized evidence from 6 systematic reviews on probiotic supplementation in human subjects, focusing on salivary function, oral microbiota, and gut health. The primary outcomes included salivary parameters (flow rate, buffering capacity, pH, biomarkers), oral microbiota changes, and gut health indicators.

Key findings suggest improvements in salivary buffering capacity and plaque pH, reductions in cariogenic bacteria such as Streptococcus mutans, and beneficial effects on gut microbiota and gastrointestinal symptoms. However, effect sizes, absolute numbers, and confidence intervals were not reported, and a meta-analysis was not conducted.

The authors note significant heterogeneity and methodological limitations across the included reviews, which reduce certainty in the findings. Adverse events, serious adverse events, and discontinuations were not reported. While the evidence suggests potential benefits, the lack of quantitative synthesis and high heterogeneity warrant cautious interpretation. Clinicians should consider these limitations when evaluating probiotic use for oral and gut health.

Study Details

Study typeMeta analysis

EvidenceLevel 1

PublishedJun 2026

View Original Abstract ↓

IntroductionProbiotics, which are classified as helpful living microorganisms, have demonstrated the ability to improve salivary function, inhibit pathogens like Streptococcus mutans, and modify the oral and gut microbiota. The aims of this systematic review was to assess their effects on salivary function, oral microbiota, and gut health.MethodsLiterature search was done in PubMed, Scopus, Web of Science, Science Direct and Cochrane were performed. Randomized controlled trials were included which involved human subjects receiving probiotic supplementation Outcomes assessed were salivary parameters (flow rate, buffering capacity, pH, biomarkers), oral microbiota changes, and gut health indicators. Study selection, data extraction, and risk of bias assessment (RoB 2.0) were performed independently by two reviewers. Due to heterogeneity, meta-analysis was not conducted.ResultsA total of six systematic reviews were included in this review. Probiotic supplementation was associated with improvements in salivary parameters, including buffering capacity and plaque pH, and reductions in cariogenic bacteria such as Streptococcus mutans. Probiotics demonstrated beneficial effects on gut microbiota and gastrointestinal symptoms, supporting an oral–gut microbiota interaction. Risk of bias ranged from low to high across studies. Overall, evidence suggested beneficial effects, though heterogeneity and methodological limitations reduced certainty.ConclusionsProbiotics have been shown to provide modest, strain-specific benefits for modulating the oral microbiota and certain salivary parameters, with more precise molecular and clinical evidence for gut effects.Systematic Review Registrationhttps://www.crd.york.ac.uk/PROSPERO/view/CRD420251243347, identifier CRD420251243347.