dark bread vs breadstuff

dark bread and breadstuff both are nouns.

Word	Noun	Adjective	Verb	Adverb
dark bread	Yes	No	No	No
breadstuff	Yes	No	No	No

As nouns, breadstuff is a hypernym of dark bread; that is, breadstuff is a word with a broader meaning than dark bread:

dark bread: bread made with whole wheat flour
breadstuff: food made from dough of flour or meal and usually raised with yeast or baking powder and then baked

Other hypernyms of dark bread include bread, staff of life.

dark bread (noun)	breadstuff (noun)
bread made with whole wheat flour	food made from dough of flour or meal and usually raised with yeast or baking powder and then baked
	flour or meal or grain used in baking bread