health food vs solid food

health food and solid food both are nouns.

Word	Noun	Adjective	Verb	Adverb
health food	Yes	No	No	No
solid food	Yes	No	No	No

As nouns, solid food is a hypernym of health food; that is, solid food is a word with a broader meaning than health food:

health food: any natural or prepared food popularly believed to promote good health
solid food: any solid substance (as opposed to liquid) that is used as a source of nourishment

Other hypernyms of health food include food.

health food (noun)	solid food (noun)
any natural or prepared food popularly believed to promote good health	any solid substance (as opposed to liquid) that is used as a source of nourishment