Heat-treated milk and dairy products encompass a plethora of both healthy and harmful molecules which impact human health. Milk proteinscontain in their encrypted sequences potential healthy bioactive peptides (BPs) which can be released by enzymes and starter lactic acid bacteriaduring food processing or by gut microbiota (GM) during gastro-intestinal transit. On the other hand, a group of hazardous heterogeneouscompounds derived from the “advanced” stage of Maillard reactions, termed the Advanced Glycation End-products (AGEs), can be formed duringprocessing and cooking of food high in sugar and proteins content. BPs and AGEs in dairy products can either prevent or promote oxidativestress, inflammation, and cardiovascular risks in healthy individuals and patients with chronic diseases, respectively. However, poor data areavailable on their content in different dairy products, on bioavailability, as well as on the role of GM in the modulation of these molecules in thecolon. The present project will apply quantitative peptidomic, proteomic, metabolomic, and metagenomic approaches to overcome these gaps andto chart the complex relationships among BPs, AGEs and colonic microbiota in healthy subjects. By applying MS/MS techniques we will quantifythe content of glycated proteins (GPs), BPs, and AGEs in raw, pasteurized, and UHT-treated milk, as well as in cheese whey, Ricotta cheese anddifferent semi-hard and hard cheeses of increasing ripening times (WP1, WP2). We will implement an in vivo dietary intervention with UHT milk inhealthy subjects to study the molecular balance between ingested GPs, BPs, and AGEs and the molecules either excreted in urine and feces orabsorbed in the blood stream (WP3, WP4, WP5). The metabarcoding analysis of fecal samples before and after dietary intervention andpeptidomic/metabolomic data will suggest intra- and inter-individual differences in GM composition and will clarify whether AGEs and BPs areproduced/degraded and absorbed not only in the small intestine but also in the colon (WP4, WP5, WP6). Biomarkers of dietary intervention will bedefined by PCoA and PERMANOVA analysis of beta diversity (WP8). Integration of metabarcoding and proteomic/peptidomic/metabolomic datawill provide potential relationships among intestinal taxa and specific AGEs or milk peptides (WP8). In vitro biotransformation assays will assessthe capability of commonly used dairy starter LAB, probiotics, and colonic bacteria to modify the most relevant AGEs and BPs (WP7). Projectresults are expected to contribute to: 1) construct a database of GPs, BPs, and AGEs in the most common dairy products; 2) identify molecularmarkers of heat treatment in different dairy food; 3) determine the kinetics of absorption and excretion of main BPs and AGEs; 4) define maincolonic taxa that putatively degrade and metabolize BPs and AGEs in vivo.