Salivary nitrate/nitrite and acetaldehyde in humans: potential combination effects in the upper gastrointestinal tract and possible consequences for the in vivo formation of N-nitroso compounds-a hypothesis

Subsequent to the dietary uptake of nitrate/nitrite in combination with acetaldehyde/ethanol, combination effects resulting from the sustained endogenous exposure to nitrite and acetaldehyde may be expected. This may imply locoregional effects in the upper gastrointestinal tract as well as systemic effects, such as a potential influence on endogenous formation of N-nitroso compounds (NOC). Salivary concentrations of the individual components nitrate and nitrite and acetaldehyde are known to rise after ingestion, absorption and systemic distribution, thereby reflecting their respective plasma kinetics and parallel secretion through the salivary glands as well as the microbial/enzymatic metabolism in the oral cavity. Salivary excretion may also occur with certain drug molecules and food constituents and their metabolites. Therefore, putative combination effects in the oral cavity and the upper digestive tract may occur, but this has remained largely unexplored up to now. In this Guest Editorial, published evidence on exposure levels and biokinetics of nitrate/nitrite/NOx, NOC and acetaldehyde in the organism is reviewed and knowledge gaps concerning combination effects are identified. Research is suggested to be initiated to study the related unresolved issues.

Automated summary

After the ingestion of nitrate/nitrite and acetaldehyde/ethanol in diet, sustained exposure to nitrite and acetaldehyde may result in combination effects. These effects could affect the upper gastrointestinal tract locally and have systemic effects on the formation of N-nitroso compounds (NOC). Salivary concentrations of nitrate, nitrite, and acetaldehyde increase after ingestion, absorption, and distribution, reflecting their plasma kinetics and secretion through the salivary glands and microbial/enzymatic metabolism in the oral cavity. Combination effects in the oral cavity and upper digestive tract have not been extensively studied. This Guest Editorial reviews the evidence on exposure levels and biokinetics of nitrate/nitrite/NOx, NOC, and acetaldehyde, and identifies knowledge gaps on combination effects. Further research is needed to address these unresolved issues.