Our body is constantly renewing all its cells and components. Some cells, like our blood cells, are all completely replaced every month. Others, are replaced, every couple or few months. By the end of a year or so, every Atom in our body has been replaced, if we are eating a proper diet.
Atoms are much like rechargeable batteries.
They store Solar Energy, by shifting electrons to higher, more energitic orbits. Our bodies release this stored Solar Energy, by returning electrons to lower more stable orbits. Plants are Nature's primary battery chargers. They collect the sun's energy and store it in the electron orbits of atoms that they have collected from the earth and air. Plants work with possibly more than 28 different atoms to work their magic.