Apple

Red Apples are found in dungeon chests and can be eaten for or crafted with gold blocks to create golden apples.

As they are very rare and heal very little health, they are not a reliable source of food. Nor is a golden apple as even though it heals all of your health, a massive amount of gold is needed to craft just one.

Trivia

 * Notch drops red apples when he dies in SMP.