The microbiota-gut-brain axis is a bidirectional homeostatic route of communication between both of the organs direct via receptors of the CNS or via epigenetic mechanisms of divers metabolites e.g. SCFA, GABA, β-hydroxybutyrate. Thus, a modulation of gut microbiota via nutrition, lifestyle etc. might be effective for emotional status and depressive disorders. The dietary composition has an influence on gut microbiota composition, microbial metabolite profile and the according consequences on emotional status and depression within a system biologic approach. There are changes in gut microbiota composition and gut microbial profile (butyrate, GABA, β-hydroxybutyrate) effecting epigenetic regulation (histone acetylation, DNA methylation) and gene expression of receptors and mediators (SLC6A4, BDNF, GABA, GPRs) involved in depressive disorders.