I'm not sure how that works with corn, but quite a few things that aren't fit for human consumption in times of plenty are quite edible in a famine, or can be made so.
You can eat field corn just fine. You shouldn't eat it raw at maturity because of the high starch content, but the solution to that is simply to harvest a bit earlier before all the starch is formed. It's not very sweet, but it's perfectly edible.
There are two primary types of corn: field corn and sweet corn. Only sweet corn can be eaten raw or lightly cooked, but field corn can be turned into edible products (e.g. cereal) with some standard processing.