Minecraft wiki entry for Hunger_management, associated text: Advantages:
Can be found relatively early on, provided there are sheep, and/or salmon nearby.
Restore 9.6 saturation.
Two pieces regenerate 19.2 saturation (equivalent to 20), filling the saturation bar completely.
Breeding sheep also supplies the player with wool.
Salmon spawn commonly in rivers and oceans in large schools, and respawn relatively quickly without needing to breed them.
Salmon can be caught in any body of water with a fishing rod.
Raw mutton and raw salmon can be cooked quickly using a campfire or soul campfire when away from a reliable source of food.
Sheep can also be killed while on fire to get cooked mutton directly.