Clay-eating, the
practice known as geophagy or geophagia, has long been a puzzle to
Western medical practitioners.
Until recently, eating chalk, soil and
other earth-related materials was seen as an abnormal behavior, one
which deprived the diet of valuable nutrients. In the southern United
States, eating clay carried a stigma; those who ate clay were labeled
“dirt eaters” or “clay eaters” and diagnosed with psychological
disorders.
Pica, the abnormal ingestion of non-food substances, remains
an official diagnosis for those who eat clay, dirt, or soil, according
to the DSM IV and the American Dietetic Association.
Outside of the medical field, however,
anthropologists and biologists are quietly revealing a more accurate
explanation for the consumption of earthen clay. |
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Culture and History of Clay Consumption
In fact, eating clay is a global practice that has existed among
humans since their evolution from primates, and one that continues today
among traditional ethnic groups as well as numerous animal species. The
practice of eating clay has been studied in present and traditional
cultures from areas across continents, including present-day Arizona and
California, Central and South America, Sweden and Sardinia, sub-Saharan
Africa, Indonesia, and Australia.
Historically, clay eating has been associated with
treatments for cholera and bacterial infection. In a practice dating
back to Greek and Roman times and later absorbed by Christianity, holy
clay tablets were widely distributed and traded throughout the
Mediterranean region and Western Europe for use in religious customs and
rituals, and as cures for poison and the plague. These clay tablets,
blessed by the Roman Catholic Church, were listed in pharmacopeia as
late as 1848.
A new picture of the clay eater gradually emerges
as the various academic disciplines examine cultures worldwide to
understand the historic benefits and the effects of eating clay. In
studies appearing in academic and scientific journals over the past
decade, the practice of earth eating is revealed as an evolutionary
behavior that in fact developed hand in hand with the early origins of
medicine.
Clay Eating Among Pregnant Women
One of the most common human
populations to engage in the deliberate consuming of earth-based
substances is that of pregnant women. In sub-Saharan Africa, the rates
of pregnant women eating soil or clay range from 28% in Tanzania to 65%
in Kenya. Clay is prepared and sold in markets, or taken from termite
mounds known to be rich in minerals, and eaten at an average of 30g
daily.
As scientists have sought an explanation for
the historical persistence of geophagy, the body’s unique needs during
pregnancy have provided the greatest clues to clay eating’s adaptive
function. |
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Pregnancy is a period of both increased nutritional
needs and increased vulnerability. In the first trimester the fetus is
particularly vulnerable to toxic insult. The pregnant mother is also
vulnerable due to a compromised immune system, suppressed during
pregnancies in order to adapt to the presence of the fetus.
Nutrition during pregnancy is increasingly demanding, especially with
regard to minerals such as iron and calcium, to support both the
growing fetus and elevated blood production. Further, this period of
nutritional need often occurs coincident with digestive difficulties
such as nausea (morning sickness) and vomiting.
Another common feature of pregnancy is pronounced
cravings. Connecting the dots, many scientists postulate that pregnant
women craving earth-like substances actually represents a biological
need associated with the demands of the body during this time. Taking
clues from this intersection of bodily demands, three theories have been
developed and studied to explain the therapeutic role of eating clay,
both among pregnant women and on a broader cultural level:
- Clay’s nutritional mineral content
- Medicinal use of clay to provide relief for symptoms of nausea and vomiting
- Protection from toxins due to the actions of clay in the digestive tract.
The presence of both current and pre-historic favored clay sites in
Africa and other parts of the world has given scientists the opportunity
to study the chemistry and mineralogy of these edible clays as they
collect evidence to support these theories.
Dirt, Minerals, and the Nutrition Hypothesis
Many of the minerals needed by the
body are, essentially, dirt or rock. Though we most often consume them
taken up in plant or animal form, nearly all mammalian species engage in
some form of direct earth eating to prevent nutritional deficiency. An
obvious example is the dietary use of salt among humans, and the
frequenting of salt licks by mammals such as deer, cattle and sheep to
obtain minerals such as sodium, calcium, iron, phosphorous and zinc.
Given this fact, the relationship between mineral deficiency
and clay and soil eating was among the first to be examined. Scientists
have hypothesized earth-eating as an adaptive behavior based on
nutritional requirements, one that occurred and persisted on an
evolutionary basis due to its survival benefits. |
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In order to test this hypothesis, Dr. John Hunter, a geologist at
Michigan State University, compared the typical daily consumption of
clays in Africa to the suggested dosage of several mineral supplements
sold in the U.S. Testing both the mineral content and bioavailability of
various clays sold for consumption in the markets of Ghana, Dr. Hunter
determined that the clays compared favorably in magnesium, potassium,
copper and zinc. The bioavailability of calcium in eaten clays reached
4% of U.S. Recommended Daily Allowance, with iron supplementation
reaching as high as 66% of RDA.
These conclusions are especially significant as calcium intake is
typically low among African populations that eat clay, and iron
deficiency affects as much as 80% of the populace, made more severe by
parasitic infection. According to Dr. Hunter, “These levels of
mineral-nutrient supplementation point clearly to the practical value of
clay eating. Normal dietary intake usually meets daily needs, and clay
eating plays a supplementary role.”
A similar study simulated human digestion in the laboratory in order
to determine the availability of nutrients in holy clay tablets
regularly consumed in by pregnant mothers in Central American Belize.
The study, published in The Geographical Review, found that pregnant
women eating clay from these tablets could supply nearly 20% of the U.S.
RDA for iron and calcium, and significant amounts of magnesium, copper
and zinc.
The nutrition hypothesis continues to be studied. While some
scientists believe iron-deficient anemia may cause a craving to eat
earth, some believe it may actually be caused by eating excessive clay.
Others note that, given the diversity of the cultures that historically
have used dietary clays and the diverse nature of the clays themselves,
it is likely that not all clays are ideal for the same set of uses or
conditions, and equally likely that the ingestion of clay does not
necessarily serve a single purpose.
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In terms of the use of clay as a mineral supplement among
pregnant women, for example, it may well be that this benefit is
secondary to other benefits, such as detoxification.
Dr. Hunter also theorizes that in examples where pica may
contribute to nutritional deficiencies, the problem may actually be the
migration of geophagy to geographical areas lacking in clay sources.
A
clear example is the consumption of laundry starch. Though the craving
and the cultural significance of eating clay was most likely transported
to the U.S. from Africa, starch is a poor substitute for clay. Dr.
Hunter states, “Lack of local clay in the concrete jungles of the North,
pressures of poverty, and stress on kinship ties with the South lead to
the consumption of laundry starch replacing traditional geophagy. But
micronutrient minerals are totally lacking in the starch.” |
Clay as a Digestive Medicinal
A more appropriate substitute for dietary clay was, however, found
among African Americans in the form of kaolin, a clay mined in North
Carolina and Georgia. Kaolin clays are available for purchase in shops
throughout the South, marketed as “down home Georgia white dirt” and
“Mississippi mud.” Those with a habit of eating kaolin clays refer to it
in slang as chalk, and themselves as “chalk-eaters”, using some of the
same references anthropologists have noted among African cultures,
comparing its taste to the smell of fresh rain and favoring certain
clays over others.
Eating chalk is not recommended, but kaolin clay may have overlooked
benefits. The digestive pharmaceutical Kaopectate was formulated using
kaolinite as its main ingredient, to aid in suppressing diarrhea and
reducing toxic effects in the digestive system. The stigma attached to
eating clay in the South may in fact be related to overuse of the
substance
Similar to many pharmaceuticals, the same actions that may
contribute to constipation and complications when taken in excess
display therapeutic benefit when taken in times of need.
Interestingly, scientists from Louisiana State University who
analyzed Nigerian clays commonly sold for consumption in West African
markets discovered their composition to be strikingly similar to that of
the clays used in medicinal Kaopectate.
In a practice perhaps precedent to industrial kaolinite mining in the
U.S., villagers outside of Uzalla, Nigeria mine the clays from a depth
of 30 to 90 cm from the surface, then sun-dry and smoke the blocks,
transforming them into a substance known locally as eko, transporting
them to market for sale throughout the region. Medicine men combine the
clay with plant substances in several medicinal remedies, half of which
are for problems associated with pregnancy, the rest used to ease
stomach ailments and dysentery. 400 to 500 tons of this medicinal clay
are produced and sold each year, a testament to their widespread use.
Given the energetic costs of diarrhea and its potentially devastating
effects when coupled with dehydration and malnutrition in children, the
ability of clay to act as an anti-diarrheal is notable. In the same
parts of Africa where pregnant women eat clay, large percentages of
children are regular clay eaters, sometimes as many as 70%. For these
children, the internal use of clay may both prevent diarrhea and enable
the body’s ability to digest valuable nutrients in food consumed
alongside clay.
Properties of Clay and Detoxification
Though the study of clay consumption
has revealed the potential for digestive and nutritional benefits,
scientists believe the most conclusive evidence points to detoxification
as a primary benefit of clay eating throughout human history. Its use
appears to be one borrowed from and shared by numerous animal species,
attesting to
its practice not as an anomaly or aberrant behavior but instead a
true adaptive practice contributing to survival and evolution.
One example from the animal kingdom is the use of clays by
animal species that regularly scavenge for a wide variety of foods,
often of varying toxicity. Researchers discovered that the ingestion of
clays by such species, among them birds, parrots, rats and primates,
enables a diverse diet without suffering the toxic effects of substances
consumed. The chemical structure of earthen clays determines their
suitability as a detoxicant. |
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Their crystalline shape includes hexagonal networks of silicon-oxygen
tetrahedrons, giving them a large surface area with which to bond with
potential toxins. In addition, hydroxyl ions and colloidal properties
within their structure promote the ability to bind and exchange metals
as well as adsorb water and other organic compounds. In cultures across
continents, anthropologists and mineralogists have documented and
substantiated the use of clays to reduce bioavailability of plant toxins
from foods and make them more edible.
These practices are known to have been used by native cultures in
present-day Bolivia, Peru and Arizona to eliminate the bitterness of
wild potatoes and prevent stomach pains and vomiting, evidenced in the
laboratory by the clay's ability to adsorb glycoalkaloids found in the
potato species.
Also documented is the practice of baking clay with acorn flour in
breads, used historically among peoples of present-day California,
Sardinia and Sweden. In examining the mineralogy of the acorn bread
clays, a study published in the American Journal of Clinical Nutrition
supports the effectiveness of clays both as adsorbers of toxins and as
contributors of trace minerals to the diet. Their function was found to
reduce the toxicity of acorns by as much as 77%, and to potentially
provide 38% of the adult RDA of Calcium.
Similarly, laboratory researchers at the University of Chicago
Department of Ecology and Evolution recently demonstrated the ability of
kaolin clay to adsorb three commonly ingested chemical toxins using a
sophisticated technique modeling the human digestive system. Clay was
found to adsorb and thus reduce the toxicity of tannic acid and quinine
by 20-30%. Researchers noted that in a true human system the effect
could be even greater due to clay’s ability to slow the movement of the
digestive process, allowing greater absorption of nutrients and greater
adsorption of toxins.
The Last Word on Eating Clay?
The study of clay eating by anthropologists, geologists,
nutritionists and ecologists has in the end come full circle to teach us
what we least expected to discover. Historians have long placed the
origins of medicine among the Greeks, with Pasteur’s breakthroughs and
the development of germ theory playing an equally important role in
shaping medicine as we know it today. It seems that this vantage point
is exactly what caused our cultural inability to understand the true
message behind the clay eater’s practice.
Puzzling over “why people eat dirt,” we labeled earth and clay as
non-food substances, but we failed to see the link between clay and our
own culturally sanctioned and regularly consumed non-food – conventional
pharmaceuticals. We failed to understand that the internal use of clay
functions as perhaps the very first medicine practiced by humans,
because it seemed outside the realm of possibility that medicine could
have been intelligently practiced in pre-historic times.
But good science is particularly adept at shifting paradigms when it
encounters them. Timothy Johns of the McGill University School of
Dietetics and Human Nutrition has published several papers examining the
evolution of early medicine. He defines medicine as the learned
behavior of ingesting substances to alleviate distress or maintain
health. He and other researchers have placed the earliest examples of
these behaviors clearly among higher primates, such as apes and
chimpanzees, who consume minerals and forage for plants to perform
non-nutritive therapeutic functions.
These behaviors are learned and passed to offspring, and, scientists
theorize, were ultimately passed on to early man. One such example was
observed and successfully analyzed by Sabrina Krief and researchers at
the National Museum of Natural History in Paris.
Chimpanzees were found
to deliberately ingest a clay as well as leaves from a certain local
tree. When analyzed under simulated digestion in the laboratory, it was
found that the action of the clay developed clear anti-malarial
properties in the leaves that were not present without the clay.
These and other examples are beginning to alter scientists
understanding, not only of clay eating, but of the roots of medicine
itself.
“Geophagy, the ingestion of nonfood, falls into the realm of
medicine,” says Johns. “As a medicine to alleviate discomfort, clay is
not different from any drug that humans in industrial and preindustrial
societies take in attempting to modify their physiological state.”
Eating clay, far from an eating disorder, may instead be history's
earliest example of using the earth's resources to solve medical
problems. With recent evidence revealing clay's common use in lowering
food toxicity and promoting digestive health, this ancient practice may
continue to have much to teach us about medicine and healing.
NOTE: We use clay for many different applications including wound healing, drawing out toxins, debris and foreign objects, detoxification of radiation and other heavy metals.. Animals will select water with clay in it before they accept plain water.
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