The effects of dietary nitrate, pH and temperature on nitrate reduction in the human oral cavity

Dietary nitrate is metabolized to nitrite by bacterial flora on the posterior surface of the tongue leading to increased salivary nitrite concentrations. In the acidic environment in the stomach, nitrite forms nitrous acid, a potent nitro sating agent. The aim of this study was to examine the effects of dietary nitrate, pH and temperature on nitrate reduction in the human oral cavity. Nitrate reduction was monitored by nitrate reduction assay based on incubation of nitrate test solutions in the mouth. Results show that all investigated factors significantly influence the reduction of nitrate in the oral cavity. With increasing levels of nitrate the amounts of nitrite in reduction assay increased, but reduction ratio (NO2/NO3) decreased in this conditions. Influence of pH on nitrate reduction is specific and in line with nature of nitrite-producing bacteria. The greatest reduction activity of bacteria is at pH 8. Variations of temperature of the oral cavity due to outdoor conditions also influence its reduction activity which is twice lower in January than in July. .