Ok, straight from the source's mouth (pun intended):
Other SCD sites advise waiting until the gut has stabilized before introducing kefir (and alcohol is not recommended with bloody diarrhea) and that care must be taken, as not all kefir has had all the lactose changed; any residual lactose can be bad at this (flair) stage.

So, I'm going to pass along the kefir suggestion, but from my own experiences with IBD, I'm inclined to agree that it best wait until the diarrhea is dried up.

Are there any vitamins/supplements that need to be replenished with this brutal kind of dehydration?

Thanks,

Doc