The salt cube does unfortunately reduce chalice healing.

Does salt cube completely invalidate chalice of blood?

Patch notes say:

The salt cube extends the duration that food keeps you full, but also reduces HP regeneration.

How would that invalidate Chalice? Chalice provides its own separate healing so long as you’re not starving. Salt Cube lowers the natural healing you get from being fed, but makes satiety drop slower. This makes Chalice much better because you get it’s extra healing for a longer period of time without needing as much food.