Intellectual and developmental disabilities (IDD) encompass both intellectual disabilities (ID) and developmental disabilities (DD). In 2016, 7.37 million people in the United States and 200 million worldwide were identified with an ID or DD. Approximately 1 in 6 (17.8%) children have been identified with a DD in the United States, which is up from 16.2% in 2009-2011. Globally, 52.9 million children from birth to 5 years of age have been identified with a DD. Registered dietitian nutritionists (RDNs) have an important role in the treatment of this population, as optimizing nutrition status improves cognition and quality of life.