A Certified Nutrition Support Dietitian (CNSD) is a registered dietitian certified in nutrition support through the independent credentialing board called The National Board of Nutrition Support Certification (NBNSC). The NBNSC was established by the American Society of Parenteral and Enteral Nutrition (ASPEN). Certification in nutrition support means that a registered dietitian has the knowledge necessary to deliver parenteral and enteral nutrition support and has passed the certification examination. Re-certification is required every five years.