Geophagy is the practice of eating earthy or soil-like substances such as clay, and chalk, in order to obtain essential nutrients such as sulfur and phosphorus from the soil. It is closely related to pica, a classified eating disorder in the DSM-IV characterized by abnormal cravings for nonfood items.
The many possible health benefits of geophagy remain under study and are much debated. Many scientists believe that it is only harmful, while others argue that there may be adaptive benefits to the practice, since humans and animal alike have engaged in it for thousands of years.
Geophagy is most often seen in rural or preindustrial societies among children and pregnant women. However, it is practiced by members of all races, social classes, ages, and sexes. In other parts of the world the practice is less stigmatized, and geophagy is not studied as a pathology but rather as an "adaptive behavior" that supplements the diet with essential nutrients or treats a disorder such as diarrhea.
In some parts of the world, geophagia is a culturally sanctioned practice. In many parts of the developing world, earth intended for consumption is available for purchase.
In parts of Africa, rural United States, and villages in India clay consumption may be correlated with pregnancy as women eat clay to eliminate nausea, possibly because the clay coats the gastrointestinal tract and absorbs dangerous toxins. The clay may also provide critical calcium for fetal development (Vemeer).
Bentonite clay is available worldwide as a digestive aid; kaolin is also widely used as a digestive aid and as the base for some medicines. Attapulgite, a substance found in clay in the Southern United States, is an active ingredient in many anti-diarrheal medicines.
Geophagy was also practiced by Native Americans in California and Peru who would eat earth with acorns and potatoes to neutralize potentially harmful alkaloids. Clay was used in the production of acorn bread in California and Sardinia, Italy.
Geophagy has also been observed in birds. Notably, many species of South American parrots have been observed at clay licks, whilst Sulphur-crested Cockatoos have been observed ingesting clays in Papua New Guinea (Discover, 1998) as well as in Glenbrook in Blue Mountains of Australia (Parrots Magazine, 2000). Analysis of most soils consumed by wild birds show that they prefer soils with high clay content, often with the smectite and bentonite clay families being well represented. In vitro and in vivo tests of these soils indicate that they release biologically important quantities of minerals like calcium and sodium, as well as adsorbing substantial quantities of small charged compounds such as alkaloids. Because the clays release minerals and adsorb other cations as part of the same process of cation exchange, it remains challenging to determine which function is the more important motivator in any given instance of avian geophagy. Separate from soil ingegstion, pet birds are often provided with grit which is retained in their gizzards to aid in grinding the food they eat.
It is also associated with iron deficiency (see Health A to Z, below)
Geophagia can be diagnosed, in absence of other evidence, by measuring the concentration of silica in feces.
Another factor keeping geophagy out of common practice for Americans is likely its association with a female practice. Geophagy is often associated with women, and most commonly, pregnant women. This presents an issue as American culture does not regularly distinguish between male and female foods. The dominant Victorian ethic in American ideology is amongst the multiple reasons that "Geophagy" became stigmatized in American culture. An ability to control appetite coupled with eating seldomly was the appropriate measure of behavior in a "civilized' American culture. Engaging in and acting upon a craving for dirt was considered uncivilized because it was seen as having a lack of self-control. A person embodying the Victorian ethic would maintain a thin figure as well as refraining from alcohol and sex. Therefore, envoking the act of "geophagy", where craving and consumption of dirt was immense, was seen as a violation to the civilized American.
Nevertheless, until recently clays like activated attapulgite and diosmectite were the active ingredient in over the counter antidiarrheal medications as they were and are among the most effective available treatment.
While the marketing of dirt in its original form would most likely not sell in the American market, geophagy may have a possible future if companies break up the dirt into its components. Several minerals or consitutents of dirt have varying therapeutic purposes. For instance, antacids or anti-diarrhea medications contain several consitutents of dirt. Although the chalky pink liquid gives a very different impression to buyers than raw earth, Americans still practice geophagy in a certain sense. Also, as described before, Americans regard the practice of digging raw dirt for consumption as a wholly uncivilized act. Yet, the American culture could potentially continue to practice geophagy if a company marketed the dirt. Americans seem to respond greater to natural products if they could purchase them from a catalog or store. The future of geophagy in the United States seemingly depends upon scientific backing, and the creation of a market or company to provide the dirt to consumers.
In a Science Digest article (Paraquat: a Potent Weed Killer is Killing People), it is recommended that a paraquat poisoning victim promptly swallow dirt, even at the risk of salmonella, because paraquat is deactivated upon contact with soil. Otherwise, a sufficiently lethal dose would cause damage to the liver, kidneys, and especially the lungs, usually causing death by asphyxiation by causing severe fibrosis. Lung transplants in two victims merely delayed their deaths because chemical levels still in their bodies subsequently damaged the transplanted lungs, too.
There is also evidence that supports the usefulness of the flora found in soil. Some have even suggested that it is useful, if not vital, in the establishment of healthy bacteria within the digestive tract, addressing the problems presented by Crohn's Disease and Leaky Gut Syndrome. Highly adsorbent families of clays have been demonstrated to cause the lining of the vertebrate gut to change both on a cellular and acellular level, potentially protecting the gut from chemical insults as well as alleviating ailments such as esophagitis, gastritis, and colitis.
Chimpanzees in Kibale National Park, Uganda have been observed to consume soil rich in kaolinite clay shortly before or after consuming plants including Trichilia rubescens, which possesses antimalarial properties in the laboratory. Simulated mastication and digestion reveals that the clay helps to release active antimalarial components from the leaves. The same type of soil is used by local healers to treat diarrhea, presumably by the same mechanism as over-the-counter antidiarrheal preparations.
There is a psychological hypothesis, which is centered around the craving ideas, reported by clay eaters. The researchers attention was directed mainly towards the pregnant and postpartum women and their emotional state. Geophagy was attributed to feelings of misery, homesickness, depression, and alienation.
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