The Oral Microbiome–Nitrate–Nitrite–Nitric Oxide Axis and Cardiovascular Health: A Narrative Review

Background: The oral microbiome has emerged as a potential contributor to cardiovascular physiology through its role in the enterosalivary nitrate–nitrite–nitric oxide pathway. Oral nitrate-reducing bacteria convert dietary nitrate into nitrite, which can subsequently be reduced to nitric oxide, a signaling molecule associated with vascular tone, endothelial function, platelet activity, and blood pressure regulation. Disruption of this pathway has been associated with reduced nitric oxide bioavailability and impaired vascular responses. Methods: This narrative review summarizes current evidence regarding the relationship between the oral microbiome, nitrate metabolism, and cardiovascular function. Relevant literature was identified through searches of PubMed/MEDLINE and Google Scholar up to May 2026. Evidence from mechanistic, observational, and interventional human studies was reviewed and synthesized thematically. Results: Available evidence suggests that oral nitrate-reducing bacteria may influence nitric oxide bioavailability and vascular function. Studies have reported associations between oral microbiome disruption and changes in blood pressure, endothelial responsiveness, plasma nitrite concentrations, and other surrogate cardiovascular markers. However, findings remain heterogeneous and are influenced by factors such as diet, oral hygiene practices, smoking status, medication use, oral health, and underlying cardiometabolic conditions. Most studies are limited by small sample sizes, short intervention durations, and reliance on surrogate outcomes rather than major cardiovascular events. Conclusions: The oral microbiome may influence cardiovascular health through its role in nitrate metabolism and nitric oxide bioavailability. However, current evidence is largely limited to surrogate vascular outcomes, while data on major cardiovascular events remain scarce. Further longitudinal and interventional studies are needed to clarify causality and evaluate microbiome-targeted interventions.