We've all seen Iron Man 1 & 2, and how Tony Stark has his little glowing Arc Reactor In His Chest.
But after Iron Man 3 he no longer has it (as per removed at the end of that film).
We all know the general attitude of Mr. Stark and how he wishes to be the best and do anything to get there, but by keeping the world in peace. Why would he purposely remove the device that can keep his body healthy and give him the ability to stay alive as long as his body will endure?
Who knows, but after Age of Ultron, he may have it back.