Mediterranean Diet and the Gut Microbiome

Irritable bowel syndrome (IBS) is the most prevalent and well-studied functional
gastrointestinal disorder. While IBS has no direct mortality, it does compromise quality of
life, incurs morbidity, and has a substantial economic impact on society. The gut microbiome
may play a significant role in the pathogenesis of IBS. Even though the exact mechanisms
underlying this relationship have not been presented, it is suggested that certain
microorganisms may increase gut permeability, activate the mucosal immune response, increase
visceral sensitivity and alter intestinal motility via a bidirectional brain-gut interaction.
Recent studies suggest that the salutary impact of the Mediterranean diet may be due to its
effects on the composition of the gut microbiome. In a recent cohort study in Italy, subjects
who adhered most closely to a classical Mediterranean diet had more favorable bacterial
enterotypes (e.g., Prevotella) in their stool, as well as higher levels of short-chain fatty
acids - which are essential for colonic function. Studies have also showed that diet alters
the predominant microbiome enterotypes and that microbiome composition can change quickly,
within 24 hours, after a dietary intervention. Therefore, consumption of a Mediterranean diet
may ameliorate the gut dysbiosis associated with IBS-D.

Inclusion Criteria:

- must be willing to eat pre-prepared foods for 4 weeks

- subjects must have no medical, religious, or cultural dietary restrictions that would
preclude their eating a Mediterranean diet.

- Phase 2 subjects- must have diagnosis of IBS based on Rome III criteria and have
diarrhea-predominant disease, defined as >50% of bowel movements characterized as
diarrhea

Exclusion Criteria:

- history of gastrointestinal disease, including celiac disease, inflammatory bowel
disease, or lactose intolerance

- diabetes mellitus

- congestive heart failure

- coronary artery disease

- chronic liver disease or end stage renal disease

- pregnancy or breastfeeding

- trainees under the direct supervision of the PI and patients receiving direct ongoing
medical care from the PI or Co-I will not be enrolled as subjects in this study