CONSUMING SOIL*

by Beatrice Trum Hunter, who is one of America's foremost food experts and an Honorary Member of NOHA. She is the recipient of the Jonathan Forman gold medal from the American Academy of Environmental Medicine for contributions to clinical ecology, the Food Editor of Consumers' Research Magazine, and the author of nearly thirty books on food issues, including Food Additives and Federal Policy: The Mirage of Safety; The Great Nutrition Robbery; and her classic Natural Foods Cookbook.


Consuming soil is regarded by the American Dietetic Association (ADA) as a phychobehavioral disorder that involves abnormal craving for, and ingestion of nonfood substances such as clay, starch, or chalk. The ADA expressed concern that such nonfood items might displace nutritious food and might be harmful

Such an assessment by health professionals may be misguided. Cravings for soil substances such as clay or chalk actually may reflect mineral deficiencies, and the individual's intuitive attempt to correct them. The practice is known as geophagia.

Soil eating was first associated with a deficiency disease of the blood as early as 1821. The disease is called chlorosis, or "green sickness" due to skin pallor. It is a form of anemia that affects adolescent girls. Chlorosis is also known as a deficiency disease in plants, characterized by yellowing of leaves. The disease, in both cases, is caused by a lack of available iron, zinc, or other minerals in the diet of humans; and in the soil, with plants. Soil eating was an attempt to obtain the needed minerals.

Cravings for soil substances such as clay or chalk actually may reflect mineral deficiencies, and the individual's intuitive attempt to correct them. The practice is known as geophagia.

Usually, humans eat clay when the demand on their nutrition is great. For example, women eat clay more frequently during pregnancy and lactation than at other periods. Children generally eat clay during their period of greatest growth, when their bodies require high levels of nutrients. In some African tribes, men have been known to eat clay prior to traveling long distances to engage in warfare.

Many women are deficient in calcium. Some clays eaten by pregnant African women provide large amounts of calcium-estimated to be as high as 80 percent of the Recommended Daily Allowance (RDA) for pregnant American women.

Clay may benefit calcium absorption. Clay retards the motility of the gastrointestinal tract and increases the time for calcium absorption from foods to take place. By binding with secondary compounds in plant foods, clay may release bound calcium and other bound minerals and make them available for absorption.

Also, it is speculated that soil eating helps pregnant women avoid the nausea and food aversions frequently experienced during the early months of pregnancy. For women whose food sources are plants with naturally occurring toxins, the clay may help absorb the toxins and render them harmless. Also, it is thought that small amounts of clay might relieve the discomfort of pregnancy by changing the stomach acidity and/or by absorbing excess saliva.

Clay may benefit calcium absorption. Clay retards the motility of the gastrointestinal tract and increases the time for calcium absorption from foods to take place. By binding with secondary compounds in plant foods, clay may release bound calcium and other bound minerals and make them available for absorption.

Patients with abnormally low levels of calcium in their blood have been known to develop such strong cravings for this mineral that they have resorted to scratching plaster off walls for consumption.

In Nepal, women in the villages, especially pregnant women, commonly consume some of the mud used to plaster their houses. Some of the mud is white, and is used for the tops of the houses. Other mud is red, and is used for the lower parts of the houses. The women eat both types.

Although soil eating is usually associated with pregnant women in the southern states of America among descendants of African slaves, who brought the custom to America, this behavior is found throughout the world. Soil or clay eating has been reported among women, especially among pregnant women, from almost every part of the world. The custom exists in Nepal, Africa, India, and Central America. It continues among Native Americans, too. In various parts of the world, and at different periods in history, entire populations have been known to consume soil.

Although soil eating is usually associated with pregnant women in the southern states of America among descendants of African slaves, who brought the custom to America, this behavior is found throughout the world.

Both in Sardinia and in Northern California, clay was added to acorn flour and water, to make traditional breads.

In earlier times, in Germany, a paste of very fine clay was substituted for butter and used to spread on bread by poor people.

In China, and elsewhere during times of severe food shortages, clay was eaten by large segments of the populations. Some clays swell in water. Samples of such clays were identified in the "famine foods" in China.

Patients with abnormally low levels of calcium in their blood have been known to develop such strong cravings for this mineral that they have resorted to scratching plaster off walls for consumption. . . . In Nepal, women in the villages, especially pregnant women, commonly consume some of the mud used to plaster their houses.

In certain areas of northeast Brazil, the prevalence of anemia in school-age children was reduced by having them eat clay. Chemical analysis revealed a high iron content in the clay they ate. (Today, iron supplements are added to their diet). The clays eaten by people in Tunisia and in the Congo were also found to contain high levels of iron.

Members of a tribe in Nigeria were known to make long journeys to a special area near Lake Chad to obtain kanwa, a certain type of soil that they ate and fed to their cattle. Nursing mothers were given a double ration. Infants from the age of eighteen months sucked lumps of kanwa.

Some individuals with pellagra, a deficiency of niacin (vitamin B3) and protein in the diet, obtained clay from special areas and carved it into sticks. They licked it as we lick candy.
Humans who consume abundant animal-based foods do not practice geophagia. For example, the Masai in Kenya, who consume large quantities of milk and blood from their cattle, are not geophagic. However, geophagia is very commonly practiced by their neighboring Kikuya, people who consume mainly plant food.

Soil Consumption in Animals
Soil consumption is widespread among animals, too. Many bird species, herbivores and omnivores, but not carnivores-consume soil. Bird carnivores, like humans who consume an abundance of animal products, do not practice geophagia. However, carnivorous animals may be seen at places where other animals assemble to seek soils for eating, because such sites offer good hunting opportunities.

East African elephants are known to return to certain hillsides for iodine-rich deposits in the soils. Scientists have observed them and claim that these elephants are especially at risk of iodine deficiency. Even their mud-wallowing practice and habit of throwing mud on their hides may be an attempt to absorb some iodine through the rich blood supply in their skin.

Soil consumption among animals appears to be an instinctive means of overcoming nutrient deficit, and/or to remove toxins from their foods. These features, too, appear in parallel with human experience.

Like humans, animals are very discriminating in their choice of soils that they select to eat. Gorillas and elephants may concentrate on favored sites and return to them repeatedly. East African elephants are known to return to certain hillsides for iodine-rich deposits in the soils. Scientists have observed them and claim that these elephants are especially at risk of iodine deficiency. Even their mud-wallowing practice and habit of throwing mud on their hides may be an attempt to absorb some iodine through the rich blood supply in their skin.

Whole troops of Rwandan mountain gorillas visit sites several times a year to dig up and eat soil located high up on the side of a volcano. The area is rich in iron and sodium-two elements that generally are very low in mountain vegetation. Like all mammals living at high altitudes, the gorillas need a good supply of iron to produce adequate numbers of red cells in their blood to maintain good health.

Many animals that eat clay can tolerate plants that contain naturally occurring toxins. The clay absorbs most of the toxins. Clays are ideal antitoxins because the very fine particles of the clay give them a large surface area to come into contact with the food toxins. The crystalline structure of the clay is layered with positively charged ions-mainly silicon and aluminum. Because many organic toxins also are composed of positively charged ions, they can exchange places with the ions in the clays and be passed harmlessly through and out of the digestive system.

. . . animals that eat clay can tolerate plants that contain naturally occurring toxins. The clay absorbs most of the toxins. Clays are ideal antitoxins because the very fine particles of the clay give them a large surface area to come into contact with the food toxins.

Animal detoxification has been observed with some tropical plant-eating birds in New Guinea. Albert Schatz, Professor of Science Education at Temple University, reported that cockatoos, parrots, and pigeons were seen to be very discriminating in choosing soils to eat. The soils were especially good in binding positively charged molecules of poisonous constituents such as strychnine, quinine, and tannic acid, present in seeds and in unripe fruits eaten by the birds. The soil in the birds' environment was not rich in any minerals that the birds required. So, they did not eat the soil for nutrients. However, when the clay was analyzed, it was found capable of binding one-tenth of its own weight in toxins, and had 50 percent more binding capacity than surrounding soils not chosen by the birds.

In many parts of Africa, domesticated animals commonly lick and eat soil. The farmers consider this practice natural and necessary for the good health and fertility of their livestock. If the animals do not eat earth in their own locality, the farmers herd them to other areas that have edible soils, or carry the soils to their animals.

In some zoos, keepers routinely feed kangaroos three to four pounds of red clay each week. The zoo veterinarians know from experience that the clay prevents oral lesions, which are similar to canine black tongue. Kangaroos in captivity are prone to develop this problem.

In some zoos, keepers routinely feed kangaroos three to four pounds of red clay each week. The zoo veterinarians know from experience that the clay prevents oral lesions, which are similar to canine black tongue. Kangaroos in captivity are prone to develop this problem.

Schatz reported that in experiments, several different clays were fed to rats. Some clays were able to compensate for deficiencies of calcium and other nutrients in the diet of nutrient-deprived rats. The clay-fed rats gained more weight than the control group. Also, they had stronger bones and suffered less tooth decay. The beneficial effects were due primarily to the calcium present in the clay. The effects varied, depending on the type of clay.

In 1997, two Canadian scientists, Susan Aufreiter and William Mahaney, analyzed the chemical compositions of soil samples from areas where geophagia is commonly practiced: North Carolina, China, and Zimbabwe. They found the soils rich in nutrients such as iodine, iron, calcium, potassium, and kaolinite.
There is a downside to clay eating. Consuming too much clay can cause intestinal blockage that needs to be unblocked surgically. Deaths from this blockage have been reported. Also, clay eating causes tooth abrasion and is suspected of causing, rather that alleviating, certain nutrient deficiencies, especially iron-deficiency anemia.

The modern aversion to the idea of soil consumption is due to a misconception. Those who eat soil do not eat surface earth, which likely is loaded with bacteria, parasites, industrial waste, dusts, pesticide residues, and other potentially harmful substances. Most edible clays are dug out of the band of clay-enriched soil that is 10 to 30 inches below the soil's surface. Usually, the extracted clay is dried or baked, which further reduces the likelihood of health hazards.

The modern aversion to the idea of soil consumption is due to a misconception. . . . Most humans are geophagists to some degree. After all, we seek sodium from salt to add to our diets. We may not view salt as a "soil" constituent, yet it is derived from a rock deposit.

Geophagia should not be regarded as some quirky practice, indulged in by small numbers of people. It is a widespread practice by both humans and animals, and appears to reflect some intuitive use of soils for various benefits. It may meet certain nutrient deficits. It may protect against plant toxins. It may relieve unpleasant symptoms in pregnancy. It may provide medicinal help.

Most humans are geophagists to some degree. After all, we seek sodium from salt to add to our diets. We may not view salt as a "soil" constituent, yet it is derived from a rock deposit. Both soil and clay contained in it are the result of rock weathering. Also, many people turn to Kaopectate, a commercial form of the clay kaolin, to relieve the distress of diarrhea.
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Allport, Susan, "Women Who Eat Dirt," Gastronomica, 2,(2): 28-37, Spring, 2002.
Aufreiter, Susan, et al. "Geochemistry & Minerology of Soils Eaten by Humans," International Journal of Food Sciences & Nutrition, 48: 393-5, 1997.
Calahan, Gerald N., "Eating Dirt," Emerging Infectious Diseases, 9(8): 1016-21, August, 2003.
Schatz, Vivian & Albert, "Some People Eat Clay & Soil," Natural Food & Farming, pages13-7, October, 1973.

*Chapter 8, "Consuming Soil," Soil & Your Health by Beatrice Trum Hunter, published by Basic Health Publications, Inc., Laguna Beach, CA, 2004. Reprinted with permission.