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The red-and-green macaw eats clay from exposed riverbanks, allowing it to utilize nutrients in harmful foods.
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. This practice is widespread among animals in the wild, as well as in human societies. Human geophagy 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. Since it is very common among animals, there is clearly some evolutionary advantage in this behaviour.

Geophagy is most often seen in rural or preindustrial societies among children and pregnant women.

Animal geophagy

Geophagy is extremely widespread in the animal kingdom. Galen, the famous Greek philosopher and physician, was the first to record the use of clay by sick or injured animals back in the second century AD. This type of geophagy has been documented in "many species of mammals, birds, reptiles, butterflies and isopods, especially among herbivores."

Geophagy is well documented 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 Guineamarker (Discover, 1998) as well as in Glenbrook in Blue Mountainsmarker 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 ingestion, pet birds are often provided with grit which is retained in their gizzards to aid in grinding the food they eat.

Human geophagy

There's considerable evidence to indicate that humans practised geophagy from the earliest times.

In human prehistory

Some scholars believe that prehistoric ancestors such as Homo erectus and Homo neanderthalensis used ochres to cure wounds as well as paint caves. Ochres are a mixture of clay and iron hydroxides.

"The oldest evidence of geophagy practiced by humans comes from the prehistoric site at Kalambo Fallsmarker on the border between Zambiamarker and Tanzania (Root-Bernstein & Root-Bernstein, 2000)." Here, a calcium-rich white clay was found alongside the bones of Homo habilis (the immediate predecessor of Homo sapiens).

Anthropological and historical evidence

Geophagy is nearly universal around the world in the tribal and traditional rural societies (although apparently it has not been documented in Japan and Korea). Also, the eating of clay (a form of geophagy) has been documented in historical sources beginning with Ancient Mesopotamia and Egypt. (Also see under medicinal clay.)

Geophagy was 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.

Current practice

While Geophagy is most often seen in tribal and rural societies among children and pregnant women, it is practiced by members of all races, social classes, ages, and sexes. 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 areas of the United States, and villages in 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 Haitimarker, the poorest economy in the Western Hemispheremarker, geophagy is widespread. The clay mud is worked into what looks like pancakes or cookies, called "bon bon de terres" (bon bons of the earth), 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.

While in the US and Europe the practice has often been stigmatized, this is not necessarily so in other parts of the world.Most non-western societies consider geophagy to be an adaptive, beneficial, and nutritional approach to promote health.There's a trend in recent scientific research to study geophagy not as a pathology, but rather as an "adaptive behavior" that supplements the diet with essential nutrients or treats a disorder such as diarrhea.

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, another type of a clay, is an active ingredient in many anti-diarrheal medicines.

Geophagy in the United States

Geophagy represents the fusion of societal nature and beliefs outside of the western world. Non westerners see dirt and clay as natural crucial elements of the world with symbolic features. This sharply contrasts the western view of dirt as impure and contaminated. This given perception explains the western world's negative connotation and repulsion with geophagy. There are also several other reasons why geophagy is considered in America to be a pathology or an eating disorder. One such reason is that geophagy is strongly associated with a minority practice. It has a stigma of being an eating habit of African slaves and poor African-Americans. Geophagy was common among slaves who were nick-named "clay-eaters" because they had been known to consume clay, as well as spices, ash, chalk, grass, plaster, paint, and starch. This stigma presents a road-block to the spreading of the practice of geophagy to the suburban white upper-middle class. Geophagy has been declining because it is deemed socially unacceptable to make dirt part of the diet.

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, invoking 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.


In the past, women who wanted to become pregnant followed the eating patterns of successful mothers instead of changing their diet according to medical studies and recommendations. As a result, geophagy has continued to pass from generation to generation. Cooked, baked, and processed dirt and clay are sold in health food stores and rural flea markets in the South. Researchers have noticed that geophagy is not as prevalent as it once was as rural Americans assimilate into urban culture. In order for geophagy to remain a part of American culture, more effective marketing strategies need to be implemented that fit into modern American culture.

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. 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.

Classification and diagnosis

The International Classification of Diseases includes geophagia among eating disorders (F50) as a variety of pica, the ingestion of non-foods. However, dirt can constitute a source of iron, although the bioavailability of such mineral has not been ascertained. For example, red clays often have iron in ferrous form, poorly absorbed by humans.

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.

Cultural explanations

The cultural meaning of dirt may be another factor that contribute to making geophagy an unacceptable practice in some cultures. Western cultures view dirt as being filthy, especially after the rise of germ theory. Dirt is similar to miasma, in that theory, which is a place where diseases are made and spread. Eating the miasma would be heretical, if not suicidal.

Furthermore, one overarching theme of Western culture is a distancing from the natural world and progress toward technology and efficiency. This movement would render geophagy unacceptable to Westerners. Evidence for this comes from the English language, with phrases like "dirt cheap" and "dirty dog." In non-western cultures, soil is thought of as being a provider for the Earth to grow, and therefore it has nutrients which can be absorbed. It came from a/the god(s) and nourishes the crops which feed the culture. In these cultures, the acceptance is not only seen by secluded tribes, but it is also accepted into the market and into families.

The persistence of geophagy within a family or community can also partially be explained by a simple mother/daughter sharing mechanism. A crucial and sometimes hazardous part of rural communities is the act of giving birth. Without advanced medical knowledge, local customs become key to a healthy outcome. Geophagy enters the picture when daughters would "follow the diet of a woman that they knew had been successful at giving birth". The maternal chain can therefore act as an important vector in the continuance of this act. The practice, in truth, is important because it does provide much needed minerals to the human body. Indeed, Western cultures have continued the practice of geophagy, but only under the guise of vitamins and minerals.

Impact on health

Health benefits

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 Parkmarker, 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.

Health risks

Like coprophagia, it may be dangerous because parasite eggs can be passed in animal feces. Baylisascaris eggs, for instance, are dropped millions at a time by raccoons and other wildlife. They can stay dormant for years, remaining viable even in extreme temperatures and drought. Some of these roundworm eggs may remain in the soil long after the feces have decomposed, and become active in the digestive tract upon being consumed. Children's predilection to engage in geophagia makes them more susceptible to worm infestations.

Other dangers associated with geophagia include damage to tooth enamel, the ingestion of a variety of bacteria, lead poisoning and intestinal obstruction.

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.

In popular culture

  • In One Hundred Years of Solitude, by Gabriel García Márquez, Rebeca exhibits symptoms of geophagy by secretly and compulsively eating the soil in the yard.
  • In the 1937 film adaptation of Pearl S. Buck's The Good Earth, during a prolonged drought, O-Lan (Luise Rainer) serves the children something to eat. Neighbors desperate for food discover that she had fed them the good earth itself, because, as she says, it is warm and gives life.
  • In the novel Survivor by author Chuck Palahniuk, (Page 172), one female Creedish cult survivor is said to have killed herself after eating dirt, or committing "Geophagy", until she experienced an esophageal rupture.
  • salad fingers, from the cartoon of the same name suffers from geophagy as well as other forms of pica
  • The idiom "to eat dirt" means to humble or humiliate oneself.


  2. Peter Abrahams, Human Geophagy: A Review of Its Distribution, Causes, and Implications. in H. Catherine W. Skinner, Antony R. Berger, Geology and health: closing the gap. Oxford University Press US, 2003, p. 33. ISBN 0195162048
  3. Jared M. Diamond, "Evolutionary biology: Dirty eating for healthy living". Nature 400, 120-121 (1999)
  4. Olle Selinus, B. J. Alloway, Essentials of medical geology: impacts of the natural environment on public health. Academic Press, 2005 ISBN 0126363412, p. 446
  5. [1] May 27, 2009 Worldfocus
  6. Dirt poor Haitians eat cookies made of mud February 19, 2009 Worldfocus
  7. Henry and Kwong, "Why is geophagy treated like dirt?"
  8. Henry and Kwong, "Why is geophagy treated like dirt?", p. 366
  9. Henry and Kwong, "Why is geophagy treated like dirt?", p. 354
  10. Henry and Kwong, "Why is geophagy treated like dirt?", p. 355
  11. Henry and Kwong, "Why is geophagy treated like dirt?", p. 357
  12. Henry and Kwong, "Why is geophagy treated like dirt?", p. 368
  13. Henry and Kwong, "Why is geophagy treated like dirt?", p. 360
  14. Henry and Kwong, "Why is geophagy treated like dirt?", p. 358-59
  15. Henry and Kwong, "Why is geophagy treated like dirt?", p. 366-368
  16. Henry and Kwong, "Why is geophagy treated like dirt?", p. 366-368
  17. Henry and Kwong, "Why is geophagy treated like dirt?", p. 365
  18. Revkin, A. C. 1983. Paraquat: A potent weed killer is killing people. Science Digest 91(6):36-38, 42, 100-104.
  19. - press release about study to be published soon: Krief S, Klein N & Fröhlich F (2008). Geophagy: soil consumption enhances the bioactivities of plants eaten by chimpanzees. Naturwissenschaften (DOI 10.1007/s00114-007-0333-0)
  20. Henry and Kwong, "Why is geophagy treated like dirt?", p. 355


  • Peter Abrahams, Human Geophagy: A Review of Its Distribution, Causes, and Implications. in H. Catherine W. Skinner, Antony R. Berger, Geology and health: closing the gap. Oxford University Press US, 2003. ISBN 0195162048

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