Many relevant materials can be found in the R call number range (especially RA: Public Aspects and RM: Therapeutics, Pharmacology), but because Diet and Nutrition comprise such a wide and interdisciplinary field, useful resources can also be found in other subject areas, including science, technology (Chemical Technology and Home Economics), and social and cultural studies.
HERE is a link to a list of subject headings in the library's collection.
The pdf below includes a detailed breakdown of the Library of Cogress' R Class: