Questions on health never change, but the answers to them do.
This would be a good question for Meta once the site is launched, but we should start thinking about it now.
The wonderful thing about health truth is that it's a constantly malleable body of information, supported simply by the (ever-expanding) research that is conducted out there.
Sometimes significant research comes to light (or even something lessor so), which changes the tune of what the previously, hailed, 'consensus' answer in the community was. The leading answer needs to be updated.
There will always be low quality or inaccurate answers in the mix, and those will be naturally downvoted by the community and not be a threat to the integrity of health information's ever-clarifying, updating and improving nature.
But at other times, there will be a well-established, well-upvoted and 'accepted' answer, that one might discover to be out-of-date in light of newly-synthesized information, in which it would seem counter-productive to try to compete with a fresh answer (and in doing so give the impression that there are two conflicting answers or points of view when really it is more that one is just more up-to-date then the other).
Would the best approach be to submit a (quality) edit, with citations and appropriate modifications of the conclusion in the answer (based on the newly-synthesized information), and let it be voted on as per the usual edit approval process?
(This possibility in and of itself gives Health SE the potential to be truly the premier Health Q&A portal on the Internet, where other sites have static, stagnant, and uneditable answers supported by now out-of-date research, which unfortunately are presented and come across as authoritative and 'final answer'. We can do something better here.)