Mediterranean-like Unprocessed (CLEAN-MED) Diet Intervention Study of the Gut Microbiome of Healthy Adults

Background: Trillions of tiny organisms-including bacteria, fungi, and viruses-live inside our intestines. These microorganisms break down nutrients in our food, aid our immunity, and help keep us healthy. The population balances among these organisms can vary in different people due to factors including genetics, lifestyle, and diet. More studies are needed to understand how dietary habits affect our intestinal microorganisms. Objective: To see how switching from a traditional Western diet (low in fiber, high in saturated fat) to a Mediterranean-like unprocessed foods diet (CLEAN-MED) changes the environment in the intestine. The CLEAN-MED diet includes lots of vegetables, fruits, and whole grains with little sugar or red meat. Eligibility: Healthy adults aged 18 to 60 Design: Participants will be divided into 2 groups. All will start with a trial week. Participants will log all the food they eat and answer questions about their diet throughout the entire study. Participants in the short-term group will eat a Western diet for 4 weeks and a CLEAN-MED diet for 4 weeks. Food will be provided for the CLEAN-MED diet. Participants will visit the clinic each week and complete surveys. They will log everything they eat. They will provide blood, urine, and stool samples. Participants in the long-term group will eat the CLEAN-MED diet for up to 12 months. They will visit the clinic each month and complete surveys. They will log everything they eat. They will provide blood, urine, and stool samples. Some foods will be provided for the first 2 weeks. Participants may choose to have a scan of their body composition every few months.