Relationship Between the Gut Microbiota and Alzheimer’s Disease: A Systematic Review

In recent years, scientific research on the gut microbiota and their relationship with some diseases, including neurological ones, has notably increased. As a result of these investigations, the so-called gut-brain axis arises. Despite its influence on the evolution and development of cognitive impairment, the gut-brain axis is little defined and demonstrated.To provide the best scientific evidence available on the relationship between the gut microbiota and Alzheimer's disease.Systematic and narrative review of the information generated in the last 5 years in national and international databases, in English and Spanish.Eight observational studies were selected, carried out in humans and, therefore, suitable for inclusion in this review.The results of these studies support the hypothesis that there is a relationship between the gut microbiota and cognitive disorders through the gut-brain axis. However, today, there is a substantial lack of human studies, especially clinical trials, which makes it difficult to formulate clinical recommendations on this topic.