Don't feed the crazy. Just say "Thanks. But that's not up for discussion." or "Thanks for telling me. What ELSE is new with you?" and change the topic.
Your personal health business is you personal health biz. You simply don't have to go there with these people. You can't really control their crazy, but you can control how YOU react to it.
Just acknowledge that your ears work and change topic. "OK. So what ELSE is new?"
Started Jan 2016: