health food vs food

health food and food both are nouns.

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

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

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

Other hypernyms of health food include solid food.

health food (noun)	food (noun)
any natural or prepared food popularly believed to promote good health	any substance that can be metabolized by an animal to give energy and build tissue
	anything that provides mental stimulus for thinking
	any solid substance (as opposed to liquid) that is used as a source of nourishment