When I was growing up one of the awful stories we'd hear about
Appalachia was that the people there were so
poor (and/or
stupid) that
they ate dirt. This is a common
stereotype about
Appalachian hillbillies (that word doesn't have to be
derogatory) but it has
a grain of truth.
Especially during the depression, (though the Appalachians have never exactly been a boom economy), people in the mountains were so badly malnourished that many of them, especially children, were driven to eating dirt. Not a lot of calories in dirt, but plenty of minerals, and it probably kept a few people alive. Not so stupid after all.
The problem these days is that people who still practice geophagy (and there are quite a few in the Southern US whose families have followed this tradition ever since it was brought from Africa) are ingesting more toxins than they are minerals. Fertilizer, pesticides, toxic runoff, lots of fun stuff in our soil these days.
Also, despite the story about the Appalachians, you can't always trust people's cravings. Driven by nutritional desperation people have been known to crave and eat things like laundry starch, ashes, chalk and lead-paint chips, all of which will make you very sick. A compulsion to eat something inappropriate like that is called pica.