The article addresses that, albeit with some hand-waving: > The activation energies for oxidation and reduction of iron are of the order of 30-60KJ/mole, compa

The article addresses that, albeit with some hand-waving: > The activation energies for oxidation and reduction of iron are of the order of 30-60KJ/mole, comparable to the figure of 57KJ/mole for ATP, a molecule which is commonly used for delivering energy around our bodies. We normally make iron from its ore at very high temperatures, because the rate-limiting process is diffusion in the solid state. But the body makes materials in a very different way, from the bottom up, atom by atom, molecule by molecule. And of course the fact is that you are already oxidizing and reducing iron inside your body all the time.