This study examines the differences between expressions used by lay persons and professionals in nutrition-related questions and answers, and to what degree General Finnish Ontology (GFO) and a medical thesaurus (FinMeSH) cover these expressions. Fifty question—answer pairs were collected in an electronic answering service. Nutrition-related concepts and their expressions with their semantic relations were identified. The vocabularies of lay persons and professionals were found to be quite similar. This hints that a special consumer health vocabulary in the field of nutrition is not needed. GFO covered 32% of all expressions in questions and 37% of expressions in answers. FinMeSH covered 33% of expressions in both groups. The overlapping match of the thesauri was low, 25% in both questions and in answers. GFO and FinMeSH were found to be poor tools for supporting users in expressing nutrition-related information needs. GFO seemed not to form a covering bridge to FinMeSH.