There is a shortage because regardless of what type of corn they grow for ethanol they still take up farm land that would normally be growing food corn. If a farmer, for instance, has 200 acres he puts into corn and decides to grow ethanol instead then that is 200 acres of corn not produced for human consumption of cattle consumption as the case may be. There is a finite amount of land for growing food, you can’t grow fuel on the land and expect not to lose production on the food corn.
Bread, when wheat was less than 2 dollars a bushel a loaf was 50 cents. Wheat is less than 4 dollars a bushel and a loaf is 2.50. You do the math.