The GW SMHS supports research in complementary and integrative approaches to treatment of sickness and disease and for health promotion. Sometimes, research may involve asking questions of patients, students, and health providers. In this study, individuals are being asked to participate in this study as either 1) a healthy volunteer, 2) a person with Mild Cognitive Impairment (MCI), or 3) a person with early Alzheimer's disease (eAD). We are trying to learn more about if the gut microbiome (the microbes that live in our digestive tract) of individuals with eAD, MCI, and healthy controls are altered following lifestyle changes. This research will provide the pilot data to begin to understand if these changes in the gut microbiome are beneficial to health and/or may slow or halt the progression of MCI or early Alzheimer's.