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===In bats===
===In bats===
There is debate over whether geophagia in bats is primarily for nutritional supplementation or detoxification. It is known that some species of bats regularly visit mineral or salt licks to increase mineral consumption. However, Voigt et al. 2008 demonstrated that both mineral-deficient and healthy bats visit salt licks at the same rate.{{cn|date=February 2015}} Therefore, mineral supplementation is unlikely to be the primary reason for geophagy in bats. Additionally, bat presence at salt licks increases during periods of high energy demand.{{cn|date=February 2015}} Voigt et al. 2008 concluded that the primary purpose for bat presence at salt licks is for detoxification purposes, compensating for the increased consumption of toxic fruit and seeds.{{cn|date=February 2015}} This was shown to be especially evident in lactating and pregnant bats, as their food intake increases to meet higher energy demands.<ref name="Selinius" />{{pn|date=February 2015}}
There is debate over whether geophagia in bats is primarily for nutritional supplementation or detoxification. It is known that some species of bats regularly visit mineral or salt licks to increase mineral consumption. However, Voigt et al. 2008 demonstrated that both mineral-deficient and healthy bats visit salt licks at the same rate.<ref name=Voigt>{{cite journal |title=Nutrition or Detoxification: Why Bats Visit Mineral Licks of the Amazonian Rainforest |author= Voigt CC, Capps KA, Dechmann DKN, Michener RH, Kun TH |journal = PLoS One |volume=3 |issue=4|date= 2008 |doi= 10.1371/journal.pone.0002011 |url=http://www.plosone.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pone.0002011&representation=PDF}}<ref> Therefore, mineral supplementation is unlikely to be the primary reason for geophagy in bats. Additionally, bat presence at salt licks increases during periods of high energy demand.<ref name=Voigt/> Voigt et al. 2008 concluded that the primary purpose for bat presence at salt licks is for detoxification purposes, compensating for the increased consumption of toxic fruit and seeds.<ref name=Voigt/> This was shown to be especially evident in lactating and pregnant bats, as their food intake increases to meet higher energy demands.<ref name="Selinius" />{{pn|date=February 2015}}


==Impact on health==
==Impact on health==

Revision as of 02:34, 26 February 2015

The red-and-green macaw eats clay from exposed riverbanks, allowing it to utilize nutrients in harmful foods.

Geophagia (also known as geophagy)[1] is the practice of eating earth or soil-like substrates such as clay or chalk. It occurs in non-human animals where it may be a normal or abnormal behaviour, and also in humans, most often in rural or preindustrial societies among children and pregnant women.[2] Human geophagia may be related to pica, an eating disorder in the Diagnostic and Statistical Manual of Mental Disorders (DSM) characterized by abnormal cravings for non-nutritive items.[3][4]

In humans

In Africa, kaolin, sometimes known as kalaba (in Gabon[5] and Cameroon[6]), calaba, and calabachop (in Equatorial Guinea), is eaten for pleasure or to suppress hunger.[6] Consumption is greater among women, especially during pregnancy.[7]

Haitian woman preparing mud cookies

In Haiti, geophagia is widespread. The clay mud is worked into what looks like pancakes or cookies, called "bon bons 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.[citation needed]

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 clay, is an active ingredient in many anti-diarrheal medicines.[8]

In the United States

According to Dixie's Forgotten People: the South's Poor Whites, geophagia was common among poor whites in the South-eastern United States in the 19th and early 20th centuries, and was often ridiculed in popular literature. The literature also states that "Many men believed that eating clay increased sexual prowess, and some females claimed that eating clay helped pregnant women to have an easy delivery."[9] Geophagia among southerners may have been caused by the high prevalence of hookworm disease, in which the desire to consume soil is a symptom.[10] Geophagia was common among slaves who were nicknamed "clay-eaters" because they had been known to consume clay, as well as spices, ash, chalk, grass, plaster, paint, and starch.[8]

Cooked, baked, and processed dirt and clay are sold in health food stores and rural flea markets in the South.[11]

Geophagia becomes less prevalent as rural Americans assimilate into urban culture.[8]

In animals

Further information: Zoopharmacognosy

Geophagy is widespread in the Animal Kingdom. Galen, the Greek philosopher and physician, was the first to record the use of clay by sick or injured animals in the second century AD. This type of geophagia has been documented in "many species of mammals, birds, reptiles, butterflies and isopods, especially among herbivores."[12]

In birds

Many species of South American parrots have been observed at clay licks,[13] and Sulphur-crested Cockatoos have been observed ingesting clays in Papua New Guinea.[14]

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.[citation needed]

The preference for certain types of clay or soil can lead to unusual feeding behaviour. For example, Peruvian Amazon rainforest parrots congregate not just at one particular bend of the Manu River but at one specific layer of soil which runs hundreds of metres horizontally along that bend. The parrots avoid eating the substrate in layers one metre above or below the preferred layer. These parrots regularly eat seeds and unripe fruits containing alkaloids and other toxins that render them bitter and even lethal. Because many of these chemicals become positively charged in the acidic stomach, they bind to clay minerals which have negatively charged cation-exchange sites, and are thereby rendered safe. Their preferred soils have a much higher cation-exchange capacity than the adjacent layers of soils that were rejected because they are rich in the minerals smectite, kaolin and mica. The preferred soils surpass the pure mineral kaolinate and surpass or approach pure bentonite in their capacity to bind quinine and tannic acid.[12] In vitro and in vivo tests of these soils indicate that they also release nutritionally important quantities of minerals such as calcium and sodium. It remains unknown which function is the more important in avian geophagia.[citation needed]

In primates

There are several hypotheses about the importance of geophagia in bats and primates.[15][16][page needed]

In bats

There is debate over whether geophagia in bats is primarily for nutritional supplementation or detoxification. It is known that some species of bats regularly visit mineral or salt licks to increase mineral consumption. However, Voigt et al. 2008 demonstrated that both mineral-deficient and healthy bats visit salt licks at the same rate.Cite error: A <ref> tag is missing the closing </ref> (see the help page). presumably by the same mechanism as over-the-counter antidiarrheal preparations.

Risks

There are obvious risks in the consumption of earth that is contaminated by animal or human feces; in particular, parasite eggs, such as roundworm, that can stay dormant for years, can present a problem. [17][18] Tetanus poses a further risk.[17] Lead poisoning is also associated with soil ingestion.[19]

Anthropological and historical evidence

"The oldest evidence of geophagy practised by humans comes from the prehistoric site at Kalambo Falls on the border between Zambia 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).[page needed][16]

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

Geophagy was practised by Native Americans in California and Peru who would eat earth with acorns and potatoes to neutralize potentially harmful alkaloids.[citation needed] Clay was used in the production of acorn bread in California and Sardinia, Italy.[citation needed] Among the Jews in the second and third centuries, a type of earth was consumed for medical purposes, but the Talmud warns about possible physiological damage from eating it.[citation needed]

Notes

  1. ^ Ziegler, J. (1997). "Geophagia: a vestige of paleonutrition?". Tropical Medicine and International Health. 2 (7): 609–611. doi:10.1046/j.1365-3156.1997.d01-359.x. PMID 9270727.
  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 0-19-516204-8
  3. ^ Sturmey P, Hersen M (2012). Handbook of Evidence-Based Practice in Clinical Psychology, Child and Adolescent Disorders. John Wiley & Sons. p. 304. See Google books link.
  4. ^ Coleman AM (2015). A Dictionary of Psychology. Oxford University Press. p. 576. See Google books link.
  5. ^ Karine Boucher, Suzanne Lafage. "Le lexique français du Gabon: K." Le Français en Afrique: Revue du Réseau des Observatoires du Français Contemporain en Afrique. 2000.
  6. ^ a b Franklin Kamtche. "Balengou : autour des mines." (Balengou: around the mines) Le Jour. 12 January 2010. Template:Fr icon
  7. ^ Callahan GN (2003). "Eating dirt". Emerging Infect. Dis. 9 (8): 1016–21. doi:10.3201/eid0908.030333. PMC 3020602. PMID 12971372.
  8. ^ a b c Henry J, Kwong AM (2003). "Why is geophagy treated like dirt?". Deviant Behavior. 24 (4): 353–71. doi:10.1080/713840222.
  9. ^ Flynt, Wayne (2004). Dixie's forgotten people: the South's poor whites. Indiana University Press. p. 40. ISBN 0-253-34513-8.
  10. ^ Gerald D. Schmidt; Larry S. Roberts (2009). "Nematodes: Trichinellida and Dioctophymatida, Enoplean Parasites". In John Janovy, Jr. (ed.). Foundations of Parasitology (Eighth ed.). McGrawHill. p. 425. ISBN 978-0-07-302827-9.
  11. ^ [dead link] ABC News, Experts claim habit of eating dirt may be beneficial for some, October 04, 2005 (accessed 17 December 09)
  12. ^ a b Diamond JM (1999). "Evolutionary biology. Dirty eating for healthy living". Nature. 400 (6740): 120–1. doi:10.1038/22014. PMID 10408435.
  13. ^ Brightsmith DJ, Taylor J, Phillips TD (2008). "The roles of soil characteristics and toxin adsorption in avian geophagy". Biotropica. 40: 766–74. doi:10.1111/j.1744-7429.2008.00429.x.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  14. ^ Symes CT, Hughes, JC, Mack AL, Marsden SJ (2006). "Geophagy in birds of Crater Mountain wildlife management area, Papua New Guinea" (PDF). Journal of Zoology. 268 (1): 87–96. doi:10.1111/j.1469-7998.2005.00002.x.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  15. ^ Krishnamani R, Mahaney WC (2000). "Geophagy among primates: adaptive significance and ecological consequences" (PDF). Animal Behaviour. 59 (5): 899–915. doi:10.1006/anbe.1999.1376.
  16. ^ a b [page needed] Olle Selinus, B. J. Alloway, Essentials Of Medical Geology: Impacts Of The Natural Environment On Public Health. Academic Press, 2005 ISBN 0-12-636341-2
  17. ^ a b Bisi-Johnson MA, Obi CL, Ekosse GE (2010). "Microbiological and health related perspectives of geophagia: an overview". African Journal of Biotechnology. 9 (36): 5784–91.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  18. ^ Brooker SJ, Bundy DAP (2014). "55 - Soil-transmitted Helminths (Geohelminths)" , in Manson's Tropical Infectious Diseases (Twenty-Third Edition), edited by Farrar, J et al., W.B. Saunders London, pp. 766–94 ISBN 9780702051012, doi:10.1016/B978-0-7020-5101-2.00056-X
  19. ^ Cook A, Ljung K, Watkins R (2011). "Human Health and the State of the Pedosphere", in Encyclopedia of Environmental Health, edited by Nriagu, J.O. Elsevier, Burlington, pp. 108–15, ISBN 9780444522726. doi:10.1016/B978-0-444-52272-6.00158-6

Further reading

  • Cooper, D.W. (2000). "Clay Eating Parrots". Parrots Magazine. 36.
  • Wiley, Andrea S. (2003). "Geophagy". In Katz, Solomon H. (ed.). Encyclopedia of Food and Culture. Vol. 2. New York: Charles Scribner's Sons. pp. 120–121.

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Geophagia&oldid=648880876"