Explains the concept of the gut-brain axis, and its implications for health and disease. Describes how microbes and their metabolites communicate with the body and the brain. Explains how the microbiome-gut-brain axis influences the development of neurodegenerative, neuropsychiatric, and neurodevelopmental disorders. Describes how microbial metabolites regulate immune and metabolic pathways in the body, and how this may impact risk of allergies, autoimmune diseases, obesity and diabetes. Explains how the ecology of the oral microbiome impacts both gut and systemic health; discusses implications for modern-day oral healthcare. Lists potential microbial and gut health disruptors, as well as therapeutic strategies to improve gut and brain health (to become “ecosystem engineers”). Describes ways in which the highly complex gut-brain scientific research has been oversold and misinterpreted by the lay press. Identifies red flags of “pseudoscience” to become a healthy skeptic. Describes how the information in this course can be utilized to improve patient care and patient outcomes.