Geophagia—the practice of eating dirt, especially claylike soils, is something animals and people have been doing for millennia.
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The standard reference guide for psychiatrists—the fourth edition of the Diagnostic and Statistical Manual for Mental Disorders (DSM-IV)—classifies geophagia as a subtype of pica, an eating disorder in which people consume things that are not food, such as cigarette ash and paint chips.
Investigators have observed geophagia in more than 200 species of animals, including parrots, deer, elephants, bats, rabbits, baboons, gorillas and chimpanzees. Geophagia is also well documented in humans, with records dating to at least the time of Greek physician Hippocrates (460 B.C.).
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[Excerpted from Scientific American]
Some examples:
In some parts of Africa, some villages of India clay consumption is correlated with pregnancy and some women eat clay to eliminate nausea, possibly because the clay coats the gastrointestinal tract and may absorb dangerous toxins. The clay may also provide critical calcium for fetal development (Vermeer).
In Haiti geophagy is widespread. The clay mud is worked into what looks like pancakes or cookies, called “bon bon de terres” (Earthy bon bons), that are dried in the sun and sold throughout the poorer areas. Small amounts of other ingredients, vegetable shortening, salt and sometimes sugar, are also added to the mix. The cookies have little or no nutritional value and are associated with various health problems.
I’ve heard some animals (chickens come to mind) eat dirt as a way to digest specific foods. Would that be considered pica?
I don’t think this would be considered pica. Pica is defined as a psychological disorder where there is an appetite for non-substantive items (no nutritional value, no function, etc.). Even if we extended this definition to chickens, or other non-human animals, we would have to determine that they have an appetite for substances like dirt. Also, because the chicken is ingesting dirt for a functional purpose, I don’t think that it fits the description of pica. However, all of this comes from the standard definition of pica as a human disorder. So maybe I am just playing around with semantics.