A couple of thoughts and clarifications for the group.
An RD program is a clinically based internship leading to an exam (the "R" for registered) and the right to use the term "Dietitian". See
www.eatright.org for more information.
An MS in nutrition is often obtained by RDs as it has become important in career advancement and obtaining leadership roles. It is not needed for hospital based practice. An MS program generally has a mix of didactics in nutritional topics with some form of final project/thesis that is highly variable. Some programs are lab research oriented, others are not.
By itself an MS in nutrition is not all that useful, although it can be a springboard to various careers, especially in the corporate world.
Neither an MS nor an RD are needed for a PhD in nutrition, although it is not uncommon for PhD applicants in nutrition to obtain an RD. The PhD in nutrition is entirely a research-based degree as with any other PhD.
With regard to an MS/MD (or MS/DO) or an MS, RD, MD training, these are very uncommon right now, although I know of several folks who went to medical school after completing their RD training. As with any other combination program, the major benefit or reason to obtain multiple degrees is the chance to have set aside time to study the discipline. The amount of cross-over with medical education is variable, but undoubtedly there is a lot one would learn in getting an MS in nutrition that is not part of most medical education programs. Again, med school curriculum programs are so variable in nutrition education that it is hard to generalize.
It would not be necessary to get an MS in nutrition to become a medical specialist in any primary area that focused on nutrition. I am unconvinced it would be all that helpful or necessary, but again this is an individual decision.
As far as the practice of medicine as related to nutrition, I can make some comments
specific to pediatrics. I say this so I don't have to say "in pediatrics" for the rest of this post, but I am
only referring to pediatrics.
Gastroenterology is combined with hepatology and nutrition as a 3 year training program after pediatric residency. (here is a well-known example
http://www.cincinnatichildrens.org/svc/alpha/g/gi/default.htm). Pediatric gastroenterologists do the usual procedures such as endoscopy but also handle a huge amount of nutrition work. They often supervise parenteral nutrition services, they consult on primary nutritional disorders such as cow milk protein allergy and they are very involved in obesity-related disorders. Some other specialties, such as neo and renal may have a large nutrition component but even these often work with the GI, hepatology and nutrition service (remember this is generally ONE service) in complex and long-term management of nutritional issues.
Research into nutrition can be done by any pediatrician or specialist, but the vast majority of pedi nutrition research is done by either neonatologists or pedi GI, hepatology and nutrition trained people. Obesity research is a focus right now, but many areas are covered by these services.
So, to summarize, I personally don't think that doing a combination degree is necessary, but have no particular negatives to say about it. In terms of careers, with regard to pediatrics, one can do general pedi or a subspecialty, but pedi GI, hepatology and nutrition as a single 3 year fellowship and board area is the most common for those interested in nutritional management and research.
