According to Christianity, as recorded in Bible:
Genesis 2:16 And the LORD God commanded the man, saying, Of every tree of the garden thou mayest freely eat:
Genesis 2:16 And the LORD God commanded the man, saying, Of every tree of the garden thou mayest freely eat: 2:17 But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.

I believe that Man was never meant to die but death became inevitable when man sinned against the Almighty God.