He is internationally known for his research on gastrointestinal motility disorders, primarily irritable bowel syndrome (IBS); gastroesophageal reflux disease (GERD); neurogastroenterology (the relationship between the central nervous system and the gut); the gut microbiome and probiotics in health and disease. A highlight of his ongoing research includes how bacteria in the digestive tract play a major role in pulling nutrients from food to nourish the body, as well as participating in protecting the body from disease.