The microorganisms in the gut live in connection with the rest of the human body. The gut-brain-axis is the key word in this context. Metabolites produced by species of the microbiota are absorbed and reach the brain and other organs, where changes are induced. Research on these aspects is constantly increasing, in particular over the past years. Researchers are looking into new options to positively influence diseases and disorders like autoimmune diseases, autism, schizophrenia, Alzheimer’s disease, Parkinson’s disease and depression via nutritional interventions. Prebiotics are often included in this research as they have a well-established positive influence on the gut microbiota. Research is also looking into brain development, mood, cognitive aspects and well-being, the influence on intrinsic inflammation processes often seen in context with diabetes and obesity, and more.