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Cultural and medical perspectives on geophagia Russell M. Reid

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Professor of Anthropology in the Department of Anthropology , University of Louisville , Louisville, KY, 40292 Published online: 12 May 2010.

To cite this article: Russell M. Reid (1992) Cultural and medical perspectives on geophagia, Medical Anthropology: Cross-Cultural Studies in Health and Illness, 13:4, 337-351, DOI: 10.1080/01459740.1992.9966056 To link to this article: http://dx.doi.org/10.1080/01459740.1992.9966056

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Cultural and Medical Perspectives on Geophagia

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Russell M. Reid Geophagia, the eating of dirt, usually clay, has been recorded in every region of the world both as idiosyncratic behavior of isolated individuals and as culturally prescribed behavior of particular societies. The behavior has long been viewed as pathological by the medical profession, and it has been claimed to be both a cause and a consequence of anemia. While there is now reason to believe that the consumption of some clays may interfere with the absorption of elemental iron, zinc, and potassium, there is little evidence for the position that geophagia, especially its culturally prescribed form, is caused by anemia. These and other maladaptive consequences of clay consumption may be offset by the adaptive value of its antidiarrheal, detoxification, and mineral supplementation potentials. Key words: geophagia, pica, anemia, antidiarrheal

Geophagia or geophagy, earth eating, is a special case of pica,! the habitual consumption of items not commonly considered to be food or the compulsive consumption of otherwise normal food items. While not universal among human societies, geophagia has been documented among humans of virtually every region of the world. In some societies it is only found as idiosyncratic behavior, especially among children, while in other societies earth and especially clay consumption may be culturally prescribed behavior (Laufer 1930). The eating of clay has periodically been described by cultural geographers, anthropologists, and medical practitioners. While the geographers and anthropologists have tended to view this practice, with the exception of idiosyncratic cases, as learned behavior conforming to the cultural expectations of the individual's society, medical practitioners have tended to assume that the practice is pathological. This review of the literature on geophagia reveals several widely held but largely undemonstrated assumptions regarding the nutritional and pathological significance of clay consumption. Some of these views have persisted in Western medical traditions for several centuries. This paper reviews three sets of literature. The first includes the body of literature that documents the distribution and history of clay consumption, especially in its culturally sanctioned forms. The second body of literature reveals the history of medical views of clay consumption and other forms of pica. In that literature there is a recurrent assumption that clay consumption is associated with RUSSELL M. REID is Professor of Anthropology in the Department of Anthropology, University of Louisville, Louisville, KY 40292. His research interests include population genetics and aspects of biocultural adaptation in human populations.

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338 R. M. Reid pathology. While variants of that assumption have become the basis for certain medical practices, we shall see that these assumptions have not necessarily been subjected to rigorous scientific validation. Even where such validation has been attempted the results have not been consistent. The third set of studies has pointed to the adaptive value of clay consumption for its antidiarrheal, detoxification, and mineral supplementation potentials.

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HISTORY AND DISTRIBUTION OF GEOPHAGIA

Over a half century ago Berthold Laufer (1930) published one of the early modern reviews of the literature on geophagia. While he did not find the practice to be universal, Laufer was able to document sporadic clay consumption on every continent. However, some of the instances reported by Laufer and in later reviews by Cooper (1957) and Halsted (1968) were isolated cases that were not culturally sanctioned. Both Cooper and Halsted also provided excellent reviews of the early literature on pica, including geophagia. Early writings dating to Rome in the sixth century A.D. report that, although pica can be found among men, women, and children, the pattern found during pregnancy is by far the most prevalent. Various explanations were given for these unusual cravings during pregnancy.2 For example, Aetius proposed that pica was caused by the suppression of the menstrual flow due to pressure by the fetus (Cooper 1957). Aegineta, on the other hand, surmised that "Pica occurs most frequently about the third month after conception because the foetus, being weak, cannot consume all of the aliment which is brought to the uterus, and hence various superfluities are collected in the stomach; and therefore they have a desire for complicated and improper articles such as extinguished coals [charcoal?], Cimolean earth, and many more such things" (Cooper 1957:5). In many cases reviewed by Laufer (1930), geophagia and particularly clay consumption was part of the traditional, culturally prescribed behavior of the society. Laufer's review revealed widespread practices of clay consumption for religious and magical purposes, for medical purposes, by pregnant and lactating women, as a famine food, or as a regular part of the diet. Explorers found earth-eating in many societies, including various Indian groups of South America. Humboldt reported that around the year 1800, clay was eaten at all times of the year by various groups along the Orinoco River, but during the two month season when the river overflowed and food was scarce the Indians seemed to subsist almost entirely on a fine clay containing iron oxide. He noted that these people appeared to be unharmed by the practice (Cooper 1957). In an extensive account by Hooper and Mann (1906) of geophagia in India, they reported the practice to be most common among pregnant women and children (Laufer 1930). More recent studies in Africa reveal that geophagia is still common (Vermeer 1966). Vermeer (1971) and Hunter (1973), working in Ghana, described the marketing of clay. This clay, usually white or gray in color, is first dug from pits, mixed with water, and pounded with a heavy pestle on a board until it is sufficiently plastic. Pieces are kneaded into various shapes and sizes, depending on the type of clay used, then dried in the sun. In the market, the different shapes

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Perspectives on Geophagia 339 and sizes identified the specific types of day. Geophagia is practiced by both children and adults. These clays are used in traditional medical preparations for diarrhea, gastric irritation associated with intestinal parasitic diseases (espedally hookworm), and during pregnancy. Vermeer (1966) examined earth eating in Nigeria and found that clay is eaten by all pregnant women of the Tiv Tribe. Both Hunter (1973) and Vermeer (1966) propose that these people consume earth as a mineral supplement during times of physical stress such as pregnancy. Laufer (1930) also reported instances of clay being consumed along with particular plants as a regular part of the diet. For example, he cited various accounts of Native Americans of the American Southwest eating clay along with bitter, raw, wild potatoes (Solanum fendlerï). He further cites accounts of Native Americans of Southern California making bread from a mixture of clay and acorn meal. Within contemporary United States, geophagia has been observed primarily among black pregnant women and children but has also been seen among others. Dickens and Ford (1942) carried out a study on black school children in Mississippi and found that 25 percent of the children had eaten "dirt" (actually reddish-brown clay) in the ten days preceding the study. Hertz (1947) described clay eating among North Carolina blacks, where it was almost solely eaten by women. These women ate a grayish-colored clay that sometimes had red streaks. The clay was taken from road banks or dirt holes and was baked in an oven to dry and harden before eating. Some women had been taught by their mothers to eat clay, others were said to have developed a craving for it when they were pregnant. Whiting (1947) found that black women in North Carolina commonly ate red and white clays. The white clay was less gritty and was preferred, although it was harder to find than red clay. This clay was also obtained from road banks. Consumption was said to be due to cravings and was most commonly seen during pregnancy. These women were also known to consume laundry starch during pregnancy. From this exploratory study, Whiting surmised that laundry starch was displacing earth consumption, a practice which he believed was dying out. Ferguson and Keaton (1950) found that 27 percent of 331 pregnant black women in Mississippi consumed clay and 41 percent consumed starch. Much smaller percentages of pregnant white women were found to consume these items. The reasons given by most of these women for eating these substances involved cravings and fear for the unborn child if the substances were not eaten. Clayton (1965) provides a most interesting description of geophagia among fifty black informants in Alabama. She also found that white clay was preferred over red clay because of its lack of grit, but found that it was more difficult to locate. The clay was usually dried in an oven before eating. Clay eating was usually begun very early in life, and children were reported to eat clay with a spoon while sitting around a "clay hole." At puberty girls began to crave it, and this craving increased during child-bearing years and especially during pregnancy. Vermeer and Frate (1975) described earth consumption in Holmes County, Mississippi. Of 56 women interviewed, ten were present consumers of clay and 22 consumed it sometimes. The clay was obtained from road cuts and beneath tree roots, and was "baked" by heating for two to three hours prior to consumption. Excavation and consumption apparently increased after rain. Consumption ranged from ten to 150 grams per day with the average daily consumption being 50 grams.

340 R. M. Reid

The mean age of the clay consumers was a little over 25 years. The authors found no evidence that the practice stemmed from physiological disorder or appetite aberration but rather that it represented a pattern of culturally transmitted behavior. Taylor (1979) found that among 155 black women interviewed in a south Texas community, 36 women had consumed earth during pregnancy. In contrast to other reports, half of these women consumed black rather than white or red clay. Baking of the clay prior to consumption was also commonly reported by these women. Describing practices in eastern North Carolina, Furuseth states:

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[G]eophagy is prevalent among children of both sexes until puberty. At this point in the child's life geophagy assumes a new meaning. To the female it becomes a symbol of womanhood . . . In contrast, black males reject geophagy at puberty . . . Geophagy takes on a special importance during pregnancy . . . The ingestion of earth provides satisfaction for an unusual craving during pregnancy. This clay represents a culturally perceived means of satisfaction for the special needs of pregnancy. [Furuseth 1973:48]

While several of these authors have used the term "craving" while describing geophagy among African American women, it is not clear what is meant by the term. Nor is it clear whether the practice was characterized as a craving by the participants or by the researchers. Similarities exist between geophagia as it appears among blacks in Africa and blacks in the United States. In both cases the highest prevalence of geophagia is among pregnant women, and the practice is clearly sanctioned during this period of life. The preferred clay is white in color and may be dried in ovens or by the sun prior to consumption. Thus, Hunter (1973) and Vermeer and Frate (1975) are led to the opinion that geophagia was culturally transferred from Africa to North America where it remains part of African American culture. Various cultures have proclaimed the medicinal qualities of earth. Among those cultures were the Greeks, Egyptians, Peruvians and Chinese who were known to use earth for treating syphilis, dysentery and diarrhea, and for increasing breast milk production and for facilitating the birth process (Laufer 1930). Terra Sigillata or Lemnian earth, a red earth, was used primarily as an antidote for poisons and for other medical purposes in the Eastern Mediterranean area as early as 40 B.C. Lozenges were made from this clay after it was mixed with goat's blood and impressed with a design or religious figure (Thompson 1912; Black 1956). A case reported from Langenburg, Baden, Germany in 1581 tells of a prisoner who, condemned to death, asked that he be given his freedom if he lived following ingestion of mercuric chloride and Terra Sigillata. The man was said to have suffered a bit but did live and was set free (Halsted 1968). Similarly manufactured panecitos benditos, small molded tablets impressed with religious images, are still in use for medicinal purposes by Zapotec Indians in Oaxaca, Mexico (Green and Jones 1968). These tablets are either chewed dry or mixed with water as a cure for stomachache or worms. Elsewhere in Central America, Black Carib women in Belize use similar tablets from Guatemala during pregnancy (Hunter and de Kleine 1984). Christopherson and Cantab (1910) described medicinal uses of earth found among the people of the Egyptian Sudan. For treatment of syphilis a heavy light-brown earth is usually mixed with honey and taken for months. For anemia, earth from a blacksmith's shop was mixed with black pepper and mustard and then

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Perspectives on Geoffoagia 341 eaten. Earth was mixed with water and taken as a preventive medicine when one moved to a new place. Beyond these medicinal uses of clay, Laufer (1930) reported the use of clay in China and elsewhere as a famine food and in the magical methods of the Taoists. In the Middle East he reported consumption of earth from holy places as an act of devotion or for magical purposes. Vermeer and Ferrell (1985) report that clay from the Nigerian village of Uzalla are components of a variety of traditional West African medical preparations for problems associated with pregnancy and to ease stomach and dysenteric ailments. Hunter (1973) reported that the traditional medical uses of clay consumption in Central Africa were for diarrheal and parasitic diseases as well as during pregnancy. Vermeer (1966) found that the Tiv of Nigeria included geophagy in traditional cures for diarrhea as well as during pregnancy. Medicinal use of clay is not limited to "folk medicine." The clay kaolin is used in the pharmaceutical preparation Kaopectate (Upjohn Co., Kalamazoo, Michigan) as an adsorbent in the treatment of diarrhea. The Nigerian clays examined by Vermeer and Ferrell (1985) were found to have "a kaolinic composition strikingly similar to that of the clays in the pharmaceutical Kaopectate" (1985:634).

MEDICAL VIEWS ON CEOPHAGIA

Although clay has been used in Western allopathic and various folk medical traditions, several widely held beliefs persist regarding the pathological implications of geophagia. Women are often thought to have food cravings during pregnancy, and most early European writers on the subject felt that they should satiate these cravings so that the unborn child would not be marked in some way. In Germany in 1562, J. F. Hubright stated the belief that cravings of pregnant women left unsatisfied would leave marks on the fetus. He advised that in lieu of unnatural foods, one should substitute dry starch for clay or plaster and black twice-baked bread for dirt (Cooper 1957). Although some early investigators tried to determine a physical cause for pica, van der Burgh in 1684 and Betten in 1687 proposed that pica must come from an unhealthy state of mind (Cooper 1957). In 1692 Maler proposed leading the sufferer away from such thinking and giving, among other medications, ashes of fossil unicorn. He also advised adding emetics to the substance desired so that nausea and vomiting would become associated with it and thus cause the patient to no longer crave it (Cooper 1957). These early reports indicate that although geophagia and other forms of pica have long been recognized in Europe, those persons who engaged in such practices were looked on as abnormal or ill. During the slave era in North America and the Caribbean there was a concern with what was called Cachexia Africana. Craigin (1835) described the symptoms of this ailment as sluggishness, fever, swelling like elephantiasis, full eyes, palpation and throbbing of the temporal arteries, small and frequent pulse at the wrists, thin watery blood of livid purple hue, shiny facial skin, ulcers of the skin, often enlarged liver, spleen and lymphatic glands and a desire to eat dirt. The sufferers were said to act idiotic except when trying to get dirt. The principal means of preventing this eating of dirt was a metallic mask with a mouthpiece which could

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342 R. M. Reid be locked. This was not a cure, Craigin added, only a deterrent. Craigin noticed that the condition was found among practically all blacks over about three years of age and that it could be found on plantations with adequate diets and relatively happy lives. Most early writers blamed Cachexia on mental depression, improper diet, overwork, and exposure to dampness, cold and filth (Twyman 1971). Representative of this school of thought was Casare Bressa who examined dirt-eating in Louisiana. Mustacchi (1971) gives an account of this early writer's work in which Bressa blamed Cachexia Africana on excessive work and a heavy overload of corn in the diet. He found that the illness was most often found among field laborers and primarily among those who drank alcoholic beverages. The condition usually started in the spring, and those afflicted did not know that they were sick. They were said to become lazy and to complain of stomach pains. Most of the summer was spent in and out of the hospital, and many of the affected would eventually die. The vital statistics of 1850, published in conjunction with the U.S. Census, listed dirt eating as a cause of death in ninety-four individuals, all but one being black. Fifty-four of these deaths occurred in Louisiana, resulting in a crude annual mortality rate of 22/100,000 bondsmen (Mustacchi 1971). Modern medical writers have also implicated geophagia in the etiology of a variety of pathological states including colon perforation (Amerson and Jones 1967), fecal impaction or acute abdomen (Wrenn 1989; Ginaldi 1988), severe tooth abrasion (Abby and Lombard 1973), kaolin granuloma of the stomach (Cohn et al. 1941), hyperkalemia (Gelfand et al. 1975) and hypokalemia (Mengel et al. 1964; Severance et al. 1988). Most of these suggestions come from isolated case histories or lack a definitive demonstration of the etiological role of geophagia. Similarities between nineteenth century descriptions of Cachexia Africana and modern descriptions of profound muscle weakness and hypokalemia have been noted (Mengel et al. 1964; Severance et al. 1988). A more common claim in the medical literature links geophagia to anemia. Even among early writers, iron therapy was often mentioned as a treatment for Cachexia Africana, along with fresh air and a more varied diet. While we should not equate Cachexia Africana with geophagia, many early writers did link the two. Mason in 1833 recommended giving blacks a necessary quantity of food, enforcing cleanliness, and furnishing proper clothing (Craigin 1835). The medical treatment he recommended was to give emetics and purgatives followed by tonic medicines that act on the digestive tract. The best tonics for this were bitter laxatives, infusions of rhubarb and ginger in a pint in which 8-10 grams of sulfate of iron had been dissolved. He states that iron can be given alone or just with water, but "it is too essential a part of the remedy to be omitted." Mason apparently assumed that anemia either resulted from or caused geophagia associated with Cachexia Africana. Discussions of anemia have dominated the recent literature on earth-consumption, with the question of which is the cause and which the effect dominating the debate. The literature on that debate prior to 1970 was reviewed by Ansell and Wheby (1972). That and the subsequent literature may be grouped into three classes: 1. Those studies which investigate the association between the presence of anemia and the practice of geophagia or other forms of pica.

Perspectives on Geophagia 343

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2. Those studies which investigate the effects of clay consumption on iron absorption. 3. Those studies which see pica as the consequence of anemia or reports of attempts to "cure" geophagia or other forms of pica by iron therapy. Among those studies seeking an association between the consumption of clay or laundry starch (a common substitute for clay) and anemia, several have found no significant relationship (Rogers 1972; O'Rourke et al. 1967). Others, however, have found lower hemoglobin levels or other indications of anemia among starch or clay eaters (Prasad et al. 1961; Sage 1962; Edwards et al. 1964; Mengel et al. 1964; Warshauer 1966; Okcuoglu et al. 1966; Keith et al. 1968; Roselle 1970). Prasad et al. (1961) describe a syndrome seen in Iran which "is characterized by marked hypochromic anemia due to iron deficiency, hepatosplenomegaly, dwarfism, lack of development of primary and secondary sexual characteristics, and a history of prolonged geophagia." It was subsequently found that this syndrome also involved zinc deficiency both in Iran (Prasad et al. 1963a) and Egypt (Prasad et al. 1963b). While geophagia was not found among the Egyptian patients, hookworm and schistosomal infections (not found in the Iranian patients) were found to be common (Prasad et al. 1963a). The same or a similar syndrome has also been reported among Turkish children (Çavdar and Arcasoy 1972). In a sample of institutionalized mentally-retarded individuals, Danford (1983) found low plasma zinc and iron levels among those practicing pica. This sample, however, included individuals who consumed twigs, string, cigarettes, paper, and other non-food items in addition to those who consumed dirt (not necessarily clay). Keith et al. (1968) has suggested that the consumption of large quantities of starch or clay by North American black women might displace iron rich foodstuffs from the diet and thus indirectly cause anemia. Studies by Edwards and associates (1964) and by Gutelius and associates (1962) found that while pica was associated with indications of anemia, clay and starch eaters had generally poorer diets than did the controls with whom they were compared. Thus, the statistical association of anemia with geophagia in several of these studies might well be spurious. Korman (1990) has reported three cases of growth retardation and anemia from celiac disease among Arab children from Gaza in which geophagia (dirt, sand, and stones) was also observed. When these children were placed on gluten-free diets, they all resumed rapid growth, the symptoms of anemia abated, and the geophagia ceased. Korman notes that anemia is often associated with celiac disease, but he makes no claim that the geophagia was either the cause or the effect of the anemia. The second set of studies reports the same association between geophagia and anemia and provides support for the view that geophagia is a cause of anemia by interfering with iron absorption. Here the concern is with cation exchange capacity of some clays as a property important in blocking iron absorption. The major support for this view comes from studies in Turkey (Minnich et al. 1968; Çavdar and Arcasoy 1972; Arcasoy et al. 1978). Subjects in the first of these studies were used as their own controls and ingested labeled ferrous sulfate with and without clay given five minutes before the test dose of iron. Clays of different cation exchange capacities differed in the extent to which they blocked iron absorption.

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344 R. M. Reid

Clay from Turkey almost totally blocked elemental iron absorption, while American clays from three sources had much less dramatic effect on iron absorption (Minnich et al. 1969). The effects of consumption of various Turkish clays and soils on impaired iron (in the form of ferrous fumarate) absorption were subsequently replicated by Çavdar and Arcasoy (1972). Talkington and his associates (1970) found that neither the ingestion of laundry starch nor of two popular Texas clays 30 minutes prior to the ingestion of labeled iron appreciably impaired iron absorption. The contrast with the results of the Turkish studies could reflect either differences in the nature of the ion exchange capacities of the clays or the longer time interval between ingestion of the clay and the iron. In short, some, but not all, clays have the capacity to block the absorption of elemental iron. Because iron from hemoglobin seems to be taken up as a porphyrin complex without conversion to a free ionized form, absorption of heme iron from meat is not necessarily hindered by clay consumption. Thus, the experimental results just summarized do not necessarily apply to all forms of dietary iron. Therefore, consumption of some types of clay do interfere with the absorption of at least some forms of iron and may play a role in the etiology of anemia. Further, the consumption of large quantities of clay or starch may displace important food items from the diet and consequently limit the quality of the diet. In addition to the evidence for a role of clay consumption in the malabsorption of iron, there is also evidence that clay consumption impedes the absorption of zinc and has led to growth retardation in Turkish children (Çavdar and Arcasoy 1972; Arcasoy et al. 1978; Çavdar et al. 1977a; Çavdar et al. 1977b; Çavdar et al. 1983). Geophagia has also been suggested as a cause of malabsorption of potassium (Mengel et al. 1964; Gonzalez et al. 1982). A third body of literature on the relationship between geophagia or other forms of pica and anemia views pica as a dietary or behavioral response to deficiencies of iron or other nutrients. Danford (1982) and Feldman (1986) refer to this as the "Nutritional Hypothesis" of the etiology of pica. This is paralleled in the literature on food craving by what Weingarten and Elston (1990:234) call the abstinence model, the view "that cravings are triggered by the dysphoric state associated with abstinence from a desired or needed substance." The evidence presented in this body of literature takes the form of medical case histories involving anemia associated with some form of pica. Most such studies report that the pica ceases with iron therapy (Lanzkowsky 1959; McDonald and Marshall 1964; Coltman 1969; Reynolds et al. 1968; Mokhobo 1986; Ferguson 1989). Crosby has taken a particularly strong stand in support of this position. "It is well established that pica, the compulsive eating of something—in this case clay—is a consequence, not the cause of iron deficiency. . . It is also well established that adequate treatment of iron deficiency promptly terminates pica" (Crosby 1982). Crosby's position is based primarily on a report by Coltman (1969) in which compulsive consumption not of clay but of ice ceased a week or two after the beginning of iron therapy. Regardless of the validity of Coltman's study, the extention of the results to geophagy are not warranted. Of those studies which deal specifically with clay consumption, Ansell and Wheby (1972) have criticized that of Lanzkowsky (1959) for its poor follow-up, lack of controls, and limited evaluation of the iron deficiency. While they found that McDonald and Marshall (1964) provided more extensive follow-up of patients, the

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Perspectives on Geophagia 345 inadequate controls and evaluation of anemia again left them with doubts. Nor is it dear what verbal messages about the evils of geophagia were received by the patients along with their iron therapy. By contrast, Gutelius and her associates (1962,1963) conducted a series of studies with careful controls in which no advice was given about pica except when it involved lead. They found that neither iron nor a multi-vitamin with minerals was significantly more effective than a placebo in curing or improving the habit of pica. Nor did they find a correlation between changes in hemoglobin levels and changes in pica. In a more recent overview of studies proposing iron deficiency and other such possible risk factors for pica, Sayetta (1986) concluded "these factors have not been established through casecontrol studies; however they derive credibility from indirect evidence." Johns and Duquette (1991:448) conclude, "although iron deficiency has been established in some forms of pica, no clear evidence has been presented to link geophagy and iron need." Weingarten and Elston (1990) are likewise skeptical of the abstinence model as an explanation of food craving. They note, for example, that pregnant or menstruating woman may state that they crave a particular food, but that they do not crave a more general class of foods or substances rich in a particular nutrient for which they might be deficient. Thus the literature on links between geophagia and anemia leads us to several conclusions. Anemia is sometimes, but not consistently, found to be associated with geophagia. The reasons for the inconsistency are several. First, depending on the cation exchange capacity of the clay that is consumed, geophagy may sometimes block the absorption of elemental iron (as well as zinc and potassium) and thus may contribute to anemia. In some, but not all, populations geophagy may, for cultural reasons, be most common among those individuals who are for other reasons at greatest risk for anemia—poorly nourished, pregnant women. In these instances, the two may be statistically associated even if they are not causally linked. The case for geophagia as a behavioral response to iron deficiency remains unconvincing.

ADAPTIVE VALUE OF GEOPHAGIA

Given the fact that culturally sanctioned geophagia is found in a wide range of human societies, it would be surprising if it did not have some adaptive value. Three such functions suggested in the literature are clay as a dietary source for minerals, clay as a component of traditional antidiarrheal preparations, and finally clay as a material which adsorbs plant toxins in the human diet. Vermeer (1966) proposed that clay consumed by pregnant women among the Tiv of Nigeria might function as a supplement to dietary minerals. Hunter (1973) reported that twelve samples of clay from markets in Ghana were found to contain phosphorus, potassium, calcium, magnesium, copper, zinc, manganese, and iron as well as nickel, cadmium, and chromium. He estimated the metabolic availability of these minerals after treatment of the clay samples with hydrochloric acid. Hunter found that the median levels of available iron and copper were about fifteen percent of the recommended dietary allowances for those minerals in pregnant

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346 R. M. Reid

women. The median levels of available calcium, zinc and manganese were in the range from 2 to 4.5 percent of their recommended dietary allowances. Levels of available phosphorus and potassium were not nutritionally significant. He concluded that, as long as the absorption of these minerals was not blocked by an undesirable cation exchange capacity of the clay, the practice of geophagia serves as a modest supplement for some mineral nutrients. Similarly, Hunter and de Kleine (1984) concluded that the average rate of consumption of holy clay tablets by pregnant women in Belize "supplies helpful amounts of calcium, potassium, magnesium, iron, zinc, copper, nickel, manganese, cobalt, and selenium" as a supplement to other dietary sources. The adaptive role of geophagia in traditional antidiarrheal preparations is more obvious. The demonstration by Vermeer and Ferrell (1985) of a kaolinic composition of traditional Nigerian pharmaceutical clays similar to that of Kaopectate has already been noted as has their use in Central Africa in the traditional treatment of diarrhea (Hunter 1973; Vermeer 1966). A third especially intriguing idea regarding the adaptive value of geophagia is supported by the recent work of Johns and co-workers (Johns 1986,1989; Johns and Duquette 1991). These studies propose that the consumption of clay along with plant materials containing toxins and other allelochemicals serves detoxification functions. Johns has provided a detailed examination of geophagous practices associated with the consumption of bitter wild potatoes containing weakly toxic glycoalkaloids, a practice he believes predates the domestication and chemical alteration of the potato. Both through physical adsorption and through ionexchange, clay is capable of adsorbing such glycoalkaloids under gastrointestinal conditions. Johns makes a similar case for the role of clay in the adsorption of tannins from acorns and points out that it is through the adsorption of diarrheacausing enterotoxins that kaolin is effective in the control of gastrointestinal upset. In addition to such dietary and bacterial toxins, Johns and Duquette (1991) also indicate that clay can adsorb "hydrogen ions in acidosis and metabolic toxins such as steroidal metabolites associated with pregnancy. All of these sources of disturbance result in common symptoms of nausea, vomiting, and diarrhea" (p. 455). This explanation also accounts for the use of clay as a famine food. During a famine we would expect to find maximal consumption of marginal, gathered plant materials and, thus, elevated risk of ingestion of plant toxins. The associated consumption of clay during such a famine would reduce the toxic risks. This approach may also throw new light on Cachexia Africana. Recalling that Casare Bressa noted complaints of stomach pain as a feature of the condition, the practice of geophagia associated with it may have been part of a folk cure rather than a cause. Johns (1990) and Johns and Duquette (1991) note that geophagy is also widely observed among animals and that rats have been shown to consume clay when exposed to chemical toxins or novel flavors in the laboratory (Mitchell et al. 1977). Further, they note that clay, especially from termite mounds, is often eaten by chimpanzees and other primates. It has been proposed that this practice serves the function of detoxifying plant materials in their diets (Hladik and Gueguen 1974; Uehara 1982). Geophagia may be viewed "as a component of the pharmophagous

Perspectives on Geophagia 347 behavior of animals that is the basis for the phenomenon of medicine that is essential to all human culture" (Johns and Duquette 1991:455).

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CONCLUSIONS

The nature and circumstances of geophagia, let alone more general pica, are far too diverse to expect a single cause or consequence. While it may be true that some anemic individuals may crave and consume unusual quantities of otherwise normal food items or materials not generally considered to be food, anemia cannot be claimed as the cause for culturally prescribed consumption of clay in those societies following such practices. This point is lost in much of the general medical literature on pica where culturally prescribed clay consumption is not differentiated from such idiosyncratic and culturally unsanctioned behavior as the eating of burnt matches, coffee grounds, large quantities of ice, or the various other forms of pica found in the general population or among institutionalized mentally retarded patients. The association between anemia and geophagia reported in medical case histories of African American women may simply reflect the facts that women, especially when pregnant, are at greater risk for anemia, and these same women may also be culturally sanctioned and encouraged to consume clay. There is no reason to conclude that they eat clay because they are anemic. On the other hand, a better case can be made that certain clays, as a result of their cation exchange capacity, interfere with the absorption of elemental iron, zinc, and potassium. This is especially to be true of clays from Turkey and elsewhere in the Middle East. Under these circumstances, geophagia could be an important contributing factor to deficiencies in these minerals. While limited testing of American clays does not suggest that they would similarly interfere with iron absorption, regular consumption of large quantities of clay or starch may displace other, more nutrient rich, items from the diet. Interference with the absorption of heme iron by clay has not been demonstrated. It would be surprising if such a widespread practice did not have some adaptive value. While certain clays may have some marginal value as mineral supplements, a stronger case can be made for the role of clay in traditional diets and medicine as an adsorber of dietary, bacterial, and metabolic toxins and hydrogen ions which give rise to nausea, vomiting, and diarrhea. Such uses of clay by humans are shared with a wide variety of other animals, including non-human primates. Most instances of culturally sanctioned geophagy may, thus, be viewed as survivals of old and widespread medical practices dealing with nausea, vomiting, and diarrhea of diverse etiologies. ACKNOWLEDGMENTS The author wishes to acknowledge the contribution of Ms. Sarah H. Taylor for her assistance in the writing of an early draft of this paper, Ms. Sharon O. Vance for her assistance proofreading the final version, and for the support for this and other faculty efforts the late Dr. Victor Olorunsola, Dean, College of Arts and Sciences, University of Louisville.

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NOTES 1. A general review of the subject of pica is beyond the scope of the present article. Indeed, some confusion has resulted in the literature when observations on other forms of pica were extended to geophagia. 2. There is considerable overlap between the literatures on geophagy, pica in general, and craving. Weingarten and Elston (1990) provide a recent review of the literature on craving and point out that it is a poorly defined phenomena. That general literature is beyond the scope of the present article.

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