Scientists have long known about the gut–brain axis —— the network linked by the vagus nerve that allows the brain and the gut to exchange information and influence each other via hormonal interactions. In recent years, it has become apparent that gut microbes are closely involved in this process. This raises questions about their relationship to diseases of the brain. Attention is focusing in particular on the connection to dementia. At the National Center for Geriatrics and Gerontology (NCGG)’s Center for Comprehensive Care and Research on Memory Disorders, scientists began researching the relationship between gut microbes and dementia in 2016. These studies have brought to light lifestyle habits that can assist in prevention.