Background: The gut-brain axis is considered a neuroendocrine system, which connects the brain and
gastrointestinal tract and plays an important role in stress response. The homeostasis of gut-brain axis is important for
health conditions and its alterations are associated to neurological disorders and neurodegenerative diseases.
Method: We selected recent papers analysing the association among alterations in the homeostasis of the gut-brain
axis and neurological disorders. In addition, we described how bioactive natural molecules - such as polyphenols –
by influencing gut microbiota composition may help rescue neural signalling pathways impaired in neurodegenerative
Results: Recent studies show that gut microbiota is a dynamic ecosystem that can be altered by external factors such
as diet composition, antibiotics or xenobiotics. Gut bacterial community plays a key role in maintaining normal brain
functions. Metagenomic analyses have elucidated that the relationship between gut and brain, either in normal or in
pathological conditions, reflects the existence of a “microbiota-gut-brain” axis. Gut microbiota composition can be
influenced by dietary ingestion of probiotics or natural bioactive molecules such as prebiotics and polyphenols. Their
derivatives coming from microbiota metabolism can affect both the gut bacterial composition and brain biochemistry.
Conclusion: This review highlights the role of gut microbiota in regulating regulates brain biochemistry and the role
of microbiota metabolites on neuropathologies. Dietary ingestion of probiotics, prebiotics and polyphenols affect gut
microbiota composition underlining the key role played by specific metabolites not only in the gut microbiota composition
but also in the brain health maintenance.