Blunted Salivary Nitrite Surge as a Predictor of Post-Glucose Microvascular and Vagal Recovery in Habitual Antiseptic-Mouthwash Users

Background: The enterosalivary nitrate–nitrite–nitric oxide (NO) pathway contributes to systemic NO bioavailability via commensal oral bacteria that reduce dietary nitrate to nitrite. Antiseptic mouthwashes, particularly chlorhexidine, suppress oral nitrate-reducing capacity, but the acute physiological consequences on autonomic and microvascular function following a metabolic challenge remain poorly characterised.Methods: This was a prospective, randomized, double-blind, placebo-controlled, parallel-group trial. Fifty healthy adults (17–32 years) were randomised (1:1) to receive 0.12% chlorhexidine (CHX, n=25) or placebo mouthwash (PLA, n=25) twice daily for seven days. On day 8, participants underwent a 75 g oral glucose tolerance test with measurements at 0, 30, 60, 90, 120, 180, and 240 minutes post‑glucose. Results: Chlorhexidine reduced oral nitrate‑reducing capacity by 65% compared to placebo (p < 0.001). Salivary nitrite concentrations were significantly lower in the CHX group at all postprandial time points, with a blunted absolute rise (9.4 vs. 32.9 μmol/L; p < 0.001) and reduced AUC₀–₂₄₀ (13,690 vs. 25,246 μmol•min/L; p < 0.001). A group × time interaction was highly significant for salivary nitrite in a mixed model analysis (Wald χ² = 347.9, p < 0.001). CHX exhibited significantly less vagal recovery (i.e., decreased late‑phase RMSSD, g = 0.80; increased LF/HF ratio, g = 3.08). The CHX group had significantly delayed microvascular reperfusion, as evidenced by increased thermal half‐time (g = 2.91), decreased perfusion recovery AUC (g = 3.65), and decreased rewarming slope (g = 3.17, p < 0.001). Salivary nitrite AUC was an independent predictor of late RMSSD (p < 0.05) and rewarming slope (p < 0.01), and oral nitrate‑reducing capacity was an independent predictor of perfusion recovery AUC (p < 0.01). The significant negative coefficients for chlorhexidine allocation remained in all models. The number of mild oral adverse events was higher in the CHX group (40% vs 8%; p = 0.018), but there were no serious adverse events.Conclusion: Findings raise important questions about the cardiovascular safety of routine antiseptic mouthwash use in healthy individuals, highlighting the need for further research and judicious clinical practice.