I know there's not a "switch", but it sure seemed like it going from fine to IBS-D after being sick.
I've been doing homemade sauerkraut, kimchi, kefir (water and milk), and making my own kombucha for years. Not much help. But I still do it. It does seem to help me not catch colds, though.
We have a snow storm on Wednesday. I think I'll do a flush that day. It can't be any worse than colonoscopy prep... I had to do a whole bottle of phospho soda...ugh.