Nucleic acids (NA) that are consumed with food are rarely considered in terms of their nutritional properties, but are mainly studied as genetic information carriers. In addition to understudied nutritional role of dietary nucleic acids (dietNA), to the best of our knowledge, there are no published study results addressing the possibility of dietNA to undergo chemical modification during food processing which might turn them into potential health risk factors. However, several existing indicators suggest such toxicological risk should be taken into account. Firstly, dietNA are conducive to oxidative processes exacerbated by thermal food processing. In red meat these reactions could be additionally accelerated by the presence of redox reactive heme iron. Secondly, the presence of oxygen gradient in the lumen of the intestine during meal consumption favours the formation of further oxidized derivatives of dietNA. Further, intestine cells are capable of absorbing modified nucleosides, so it is also very likely that oxidized products of dietNA digestion can be absorbed as well. Enterocytes are characterized by the increased activity of enzyme triphosphatase MTH1, which hydrolyses triphosphates linked to oxidized purine nucleosides in triphosphate nucleoside pool. This is considered as a protection against incorporation of oxidized nucleotides of exogenous source to the replicating host DNA. The proposed project will address the hypothesis that exposure of alimentary tract cells to chemically modified dietNA or their components may pose toxicological risk. The purpose of the first part of the project will be the qualitive and quantitative assessment of the oxidized derivatives of dietNA occurring as a result of thermal processing of meat. Meat samples differing in heme iron content will be selected for testing. The purpose of the second part of the project will be to investigate the effect of oxidatively modified dietNA or its oxidised components on the functioning of digestive tract cells. Cytotoxicity and genotoxicity will be tested in in vitro models. Each test will be performed in the absence or presence of the inhibitor of MTH1 enzyme. The proposed research is expected to provide currently not available experimental data. Obtained results will be published in recognized peer-reviewed scientific journal.