Dietitians and nutritionists are both food and nutrition experts. They've studied how diet and dietary supplements affect your body and your health. Both are considered to be healthcare professions. However, the two titles shouldn't be used interchangeably.
Dietitians
According to the Academy of Nutrition and Dietetics (United States), a registered dietitian is someone who has:
- Earned a bachelor's degree with course work approved by the Academy of Nutrition and Dietetics' Accreditation Council for Education in Nutrition and Dietetics.
- Completed an accredited, supervised practice program at a healthcare facility, community agency or foodservice corporation.
- Passed a national examination administered by the Commission on Dietetic Registration.
- Completed continuing professional educational requirements to maintain registration.
A registered dietitian may plan food and nutrition programs and promote healthy-eating habits to prevent and treat illness. They often work in food service or as part of medical teams in hospitals, clinics and other healthcare facilities. Dietitians also work in university settings, where they may teach, do research or focus on public health issues.
In the United States, the Academy of Nutrition and Dietetics also credentials dietetic technicians, registered. These dietetic technicians typically have an associate's degree and work with registered dietitians. They're allowed to use the letters D.T.R. after their name.
Nutritionists
A nutritionist is someone who's studied nutrition and may have a graduate degree (M.S. or Ph.D.) in nutrition from an accredited college. Dietitians are considered to be nutritionists, but not all nutritionists are dietitians.
Some healthcare providers (medical doctors, osteopaths, physician assistants, chiropractors and naturopathic doctors) may be considered to be nutritionists if they've completed extra study in the area of nutrition and they may practice "clinical nutrition." This type of nutrition is often considered part of alternative or complementary medicine.
According the University of Maryland Medical Center, clinical nutrition includes:
"The science of nutrients and how they are digested, absorbed, transported, metabolized, stored, and eliminated by the body. Besides studying how food works in the body, nutritionists are interested in how the environment affects the quality and safety of foods, and what influence these factors have on health and disease."
There are nutritionist certification boards, such as the Certification Board for Nutrition Specialists, which requires applicants to have at least a master's degree in nutrition (or related field) from an accredited college along with practical experience before sitting for their certification exam. Nutritionists who pass this test may refer to themselves as certified nutrition specialists (C.N.S.), which is a protected title. The Clinical Nutrition Certification Board is another organization that offers certification as the certified clinical nutritionist (C.C.N.).
Licensure
While only a dietitian can use the title "dietician," it's important to understand that the term "nutritionist" itself is not protected, so in regions where nutrition and dietetics are not licensed or regulated, anyone can call themselves a nutritionist, even if they're not qualified. Many (but not all) U.S. states and Canadian provinces require licensure to practice as either a dietitian or a nutritionist. They are:
- L.D. = licensed dietitian
- L.N. = licensed nutritionist
- L.D.N. = licensed dietitian nutritionist
The requirements for licensure vary a bit by location. Some states only license register dietitians, while others license nutritionists if they're certified by one of the above certification boards.
Sources:
Academy of Nutrition and Dietetics. "What are the qualifications of a registered dietitian?" Accessed January 23, 2012. http://www.eatright.org/Public/content.aspx?id=6713.
University of Maryland Medical Center. "Nutrition." Accessed January 23, 2012. http://www.umm.edu/altmed/articles/nutrition-000357.htm.


