Serum samples were taken from four healthy donors before a meal and 3, 5, 7, 9 h after a meal (Supplementary Table S6, Sheet 1). The analysis of the serum peptidome against the HuMiProt90 database showed that the amount of non-human peptides (potentially bacterial peptides) in the bloodstream significantly increased 5 h after a meal (Figure 3D, Supplementary Table S6, Sheet 3). The comparison of these data with the transit time of food in different parts of the gastrointestinal tract suggests that bacterial peptides enter the bloodstream predominantly in the small intestine. At the same time, phyla Proteobacteria, Firmicutes and Actinobacteria are the main contributors to the increase in (potentially) bacterial peptides 5 h after a meal (Supplementary Table S6, Sheets 5 and 6).