The article reports that geophagia is present in many parts of the world, but from the examples mentioned, it seems to be most prevalent among African children and pregnant women.    From Wordnik.com.  [Let them it dirt!] Reference

(Via Archinect Forum.) 3) Cabinet Magazine on geophagia.    From Wordnik.com.  [Prunings XLIII] Reference

(1999) Nematode intestinal parasites of children in rural Guinea, Africa: prevalence and relationship to geophagia.    From Wordnik.com.  [PLoS ONE Alerts: New Articles] Reference

3 Cabinet Magazine on geophagia.    From Wordnik.com.  [Archive 2008-05-01] Reference

The consumption of the latter, sometimes called geophagy or geophagia, a Greek term meaning "earth-eating," is the most commonly noted type of pica, and some researchers today believe that it may be a response to fill a nutritional deficiency, such as low iron or calcium. 89 Clay consumption can lead to several health problems, however, such as liver and kidney damage, constipation, abdominal problems, mercury poisoning, and anemia.    From Wordnik.com.  [Pestilence and Headcolds: Encountering Illness in Colonial Mexico] Reference