Abstract
The varied mineralogical composition of earthy materials and the quantity of elements extracted by simulated stomach acid substantiate the diversity of materials consumed by humans practicing geophagy. Direct consumption of ‘edible earths’ for medicinal and spiritual purposes occurs worldwide and is deeply rooted in ‘folk medicine’ and religion. The legends associated with the healing powers of the clay from Chimayo, New Mexico, provide an excellent example of the roots of geophagy. The clay mineral assemblages revealed by X-ray diffraction analysis of 22 samples from New Mexico, North America, and other parts of the world are highly variable. One might be monominerallic kaolinite or smectite, and another, a complex mixture of illite, kaolinite, smectite, and chlorite or vermiculite. The quantities of elements (Al, Si, K, Na, Ca, Mg, Fe, Mn, Ti, P, S, Ba, Sr, Pb, Zn, Cd, Co, Cu, Cr, Ni, V, Zr, Se, Mo, Be, Sb, and As) extracted by 0.12 M HCl varied from ∼1.0 mg/g to the limit of detectability, 0.0001 mg/g. Potential long-term human health effects were evaluated with the Reference Dose Ratio (RDR). It divides the quantity of the element extracted from 50 g of the total sample by the recommended reference dose (RfD) reported in the Environmental Protection Agency’s (EPA, USA) IRIS (Integrated Risk Information System) database. Median RDR values for Na, Cr, Sb, and As exceeded 1.0 indicating an abnormally high potential intake. Materials consumed by humans are so varied that caution should be used in comparing the results of one clay study with those of another without mineralogical and chemical data.
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References
Abrahams, P. W. (1997) Geophagy (soil consumption) and iron supplementation in Uganda. Tropical Medicine and Institutional Health, 2, 617–623.
Abrahams, P.W. (2005) Geophagy and the involuntary ingestion of soil. Pp. 435–458 in: Essentials of Medical Geology (O. Selinus, editor-in-chief). Elsevier, Amsterdam.
Abrahams, P.W. and Parsons, J.A. (1997) Geophagy in the Tropics: an appraisal of three geophagical materials. Environmental Geochemistry and Health, 19, 19–22.
Barltrop, D., Strehlow, C.D., Thornton, I., and Webb, J.S. (1974) Significance of high soil lead concentrations for childhood burdens. Environmental Health Perspectives, 7, 75–82.
Carretero, M.I. and Lagaly, G., editors (2007) Clays and health: An introduction. Applied Clay Science, 36, 1–3.
Carretero, M.I., Gomes, C.S.F., and Tateo, F. (2006) Clays and human health. Pp. 717–741 in: Handbook of Clay Science (F. Bergaya, B.K.G. Theng, and G. Lagaly, editors). Developments in ClayScience, 1, Elsevier, Amsterdam.
Dissanayake, C. (2005) Of stones and health: Medical geology in Sri Lanka. Science, 309, 883–885.
Ferrell, R.E., Vermeer, D.E., and LeBlanc, W.S. (1985) Chemical and mineralogical composition of geophagical materials. Trace Substances in Environmental Health XIX, Universityof Missouri, pp. 47–55.
Gelfand, M.C., Zarate, A., and Knepshield, J.H. (1975) Geophagia: A cause of life-threatening hyperkalemia in patients with chronic renal failure. Journal of the American Medical Association, 234, 738.
Gomes, C.S.F. and Silva, J.B.P. (2007) Minerals and clay minerals in medical geology. Applied Clay Science, 36, 4–21.
Hooda, P.S., Henry, C.J.K., Seyoum, T.A., Armstrong, L.D.M., and Fowler, M.B. (2004) The potential impact of soil ingestion on human mineral nutrition. Science of the Total Environment, 333, 75–87.
Hunter, J.M. and de Kleine, R. (1984) Geophagy in Central America. The Geographical Review, 74, 157–168.
Hunter, J.M., Horst, O.M., and Thomas, R.N. (1989) Religious geophagy as a cottage industry: The holy clay tablet of Esquipulas, Guatemala. National Geographic Research, 5, 281–295.
Gonzalez, J.J., Owens, W., Ungaro, P.C., Werk, E.E., and Wentz, P.W. (1982) Clay ingestion: a rare case of hypokalemis. Annals of Internal Medicine, 97, 65–66.
Johns, T. and Duquette, M. (1991) Detoxification and mineral supplementation as functions of geophagy. American Journal of Clinical Nutrition, 53, 448–456.
Katz, J.M. (2008) Hungry Haitians eat mud as cost of food soars. The Advocate, Wednesday, January 30, 2008, p. 3A.
Ljung, K., Selinus, O., Otabbung, E., and Berglund, M. (2006) Metal and arsenic distribution in soil particle sizes relevant to soil ingestion by children. Applied Geochemistry, 21, 1613–1624.
Mahaney, W.C. and Krishnamani, R. (2003) Understanding geophagy in animals: Standard procedures for sampling soils. Journal of Chemical Ecology, 29, 1503–1523.
Mascolo, N., Summa, V., and Tateo, F. (1999) Characterization of toxic elements in clays for human healing use. Applied Clay Science, 15, 491–500.
Minnich, V., Orcuoglu, A., Tarcon, Y., Argosy, A., Cin, S., Yorupoglu, O., Raenda, F., and Demirag, B. (1968) Pica in TurkeyII: Effect of clayupon iron absorption. American Journal of Clinical Nutrition, 21, 78–86.
Oomen, A.G., Hack, A., Minekus, M., Zeijdner, E., Cornelis, C., Schoeters, G., Verstraete, W., van de Wiele, T., Wragg, J., Rompelberg, C.J.M., Sips, A.J.A.M., and van Wijnen, J.H. (2002) Comparison of five in vitro digestion methods to study the bioaccessibility of soil contaminants. Environmental Science and Technology, 36, 3326–3334.
Padilla, F.V. and de la Torre, A.M. (2006) La pica: retrado de una entidad clinica poco conocida: Nutricion Hospitalaria, 21, 557–566.
Petschick, R. (2004) MacDiff 4.2.5. Powder diffraction software. Available from: https://doi.org/servermac.geologie.uni-frank-furt.de/Staff/Homepages/Petschick/RainerE.html
Reinbacher, W.R. (2003) Healing Earths: The Third Leg of Medicine. Published by the author, ISBN: 1-4033-5090-5, 244 pp.
Robertson, R.H.S. (1986) Fuller’s Earth: A History of Calcium Montmorillonite: Volturna Press, Mineralogical Society, London, occasional publication.
Robertson, R.H.S. (1996) Cadavers, choleras, and clays. Mineralogical Society Bulletin, 113, 3–7.
Ruby, M.V., Davis, A., Schoof, R., Eberle, S., and Sellstone, C.M. (1996) Estimation of lead and arsenic bioavailabilty using a physiologically based extraction test. Environmental Science and Technology, 30, 422–430.
Smith, B., Rawlins, B.G., Cordeiro, M.J.A.R., Hutchins, M.G., Tiberindwa, J.G., Sserunjogi, L., and Tomkins, A.M. (2000) The bioaccessibility of essential and potentially toxic trace elements in tropical soils from Mukono District, Uganda. Journal of the Geological Society of London, 157, 885–891.
Tateo, F. and Summa, V. (2007) Element mobilityin clays for healing use. Applied Clay Science, 36, 64–76.
Tateo, F., Summa, V., Gianossi, M.L., and Ferrero, G. (2006) Healing clays: Mineralogical and geochemical constraints on the preparation of clay-water suspension (‘argillic water’). Applied Clay Science, 33, 3–4.
Vermeer, D.E. and Ferrell, R.E. (1985) Nigerian geophagical clay: A traditional antidiarrheal. Science, 227, 634–636.
Vermeer, D.E. and Frate, D.A. (1979) Geophagy in rural Mississippi: Environmental and cultural contexts and nutritional implications. American Journal of Clinical Nutrition, 32, 2129–2135.
Williams, L.B., Holland, M., Eberl, D.D., Brunet, T., and Brunet de Courrsou, L. (2004) Killer Clays! Natural antibacterial clay minerals. Mineralogical Society Bulletin, 139, 3–8.
Williams, L.B., Haydel, S.E., Giese, R.S., Jr., and Eberl, D.D. (2008) Chemical and mineralogical characteristics of French green clays used for healing. Clays and Clay Minerals, 56, 437–452.
Wilson, M.J. (2003) Clay mineralogical and related characteristics of geophagic materials. Journal of Chemical Ecology, 26, 1525–1547.
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Ferrell, R.E. Medicinal clay and spiritual healing. Clays Clay Miner. 56, 751–760 (2008). https://doi.org/10.1346/CCMN.2008.0560613
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DOI: https://doi.org/10.1346/CCMN.2008.0560613