"Registered Dietitian Nutritionists (RDNs) are food and nutrition experts with a minimum of a graduate degree from an accredited dietetics program and who completed a supervised practice requirement, passed a national exam and continue professional development throughout their careers," states the Academy of Nutrition and Dietetics on the eatright.com site.
Credentialed professions identify their practitioners as trained experts. It’s a qualification in a profession, much like the MD credential for your primary care medical provider, aka, your physician or doctor. Registered Dietitian Nutritionists (RDNs) are credentialed practitioners in the nutrition and dietetics profession. Most often when someone uses the term “dietitian”, they are referring to an RDN.
As a legally protected title, “Registered Dietitian Nutritionist” is only awarded to those practitioners who successfully completed specific educational requirements, passed a national exam, and continue life-long learning through a focused professional development plan reviewed by a nationally recognized credentialing agency. For the RDN, this agency is known as the Commission on Dietetics Registration.
It is illegal for any other practitioner to use the title of RDN. Many states are also adopting the title “Board Certified Dietitian” or "Licensed Dietitian" to distinguish the RDN as the nutrition expert in their state.
Often confusing to the consumer is the term “nutritionist” Anyone can call themselves a “nutritionist”. There is no legal or even standardize definition of this term. Nor is there any entity regulating its user's educational background, training, and ethical behavior which may result in unqualified health care recommendations that cause people harm.
No matter what someone calls themselves “dietitian” or “nutritionist”, check their credentials to make certain you are employing a qualified nutrition expert to work with you to reach your nutrition and well-being goals. (1)
(1) "What is an RDN?", Eatright.org. https://www.eatright.org/about-rdns-and-ndtrs Accessed 2025.03.04