nutritionist vs specialist

nutritionist and specialist both are nouns.

Word	Noun	Adjective	Verb	Adverb
nutritionist	Yes	No	No	No
specialist	Yes	No	No	No

As nouns, specialist is a hypernym of nutritionist; that is, specialist is a word with a broader meaning than nutritionist:

nutritionist: a specialist in the study of nutrition
specialist: an expert who is devoted to one occupation or branch of learning

Other hypernyms of nutritionist include specialiser, specializer.

nutritionist (noun)	specialist (noun)
a specialist in the study of nutrition	an expert who is devoted to one occupation or branch of learning
	practices one branch of medicine