I asked a question about recommended daily intake and it is on hold for being "too broad", but in many other sites i participate on SE have some questions that cover a whole topic that would be normally too broad, but they are kept to be a source from information for other questions that ask about the same thing.
Like this example on InfoSec.se it could be a a too broad question, but it's kept because prevent the site from being flooded by questions about the same thing.
Do we want to have 100 questions about vitamins C,B,A(for example)....or just one that cover them all?