Key Takeaways
Registered dietitians (RDs), also called registered dietitian nutritionists (RDNs), are food and nutrition experts uniquely trained in the nutritional treatment of disease, disease prevention, and overall health promotion and well-being.
RDs and RDNs have a degree from an accredited dietetics program, have completed supervised practice, have passed a registration exam, and must accrue continuing education hours.
Nutritionists are not regulated in many states, and therefore, anyone can call themselves a nutritionist; their certifications are often unregulated.
A dietitian, also known as a registered dietitian (RD) or registered dietitian nutritionist (RDN), completes a supervised practice program, passes a national registration exam, and helps treat medical conditions.

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