Steps to reproduce:
1.start a new world in survival
2. Mine 17 blocks of dirt
3. Stack yourself up with the dirt.
4. Jump off the pillar.
Expected result:
Health regenerates fully without the hunger bar affected in major ways
Actual Result:
The entirety of a player's saturation is removed in less than half a minute, and the hunger bar depletes to 16 without health fully regenerating.

This is a major issue that makes it much harder to start a survival world as even a single hit from a mob can make it impossible to regenerate more health afterward, forcing the player to desperately look for food instead of doing almost anything else, such as looking for ore in caves for better equipment.