Golden Berries, crafted just like a Golden Carrot, only instead using sweet berries instead of a carrot. Golden Berries can be used to craft Potions of Alexiteric, these give immunity against poison and wither effect for 3 minutes. (Your health bar changes appropriately) Potions of Alexiteric are extendable to 8 minutes by adding redstone.
Golden Berries are farmable.