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| Digging Into the Dirt | Digging Into the Dirt |
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| If you want to eat dirt, Sera L. Young can tell you where to get it online, why it might have some benefits and some risks, and perhaps give you a new idea about why you, and many other people crave it. | If you want to eat dirt, Sera L. Young can tell you where to get it online, why it might have some benefits and some risks, and perhaps give you a new idea about why you, and many other people crave it. |
| But even if you’re not about to order “white dirt” from Sam’s General Store in White Plains, Ga., there’s a lot to learn in “Craving Earth: Understanding Pica: The Urge to Eat Clay, Starch, Ice and Chalk,” Dr. Young’s intriguing investigation of a taste for earth that humans share with lots of other animals. | But even if you’re not about to order “white dirt” from Sam’s General Store in White Plains, Ga., there’s a lot to learn in “Craving Earth: Understanding Pica: The Urge to Eat Clay, Starch, Ice and Chalk,” Dr. Young’s intriguing investigation of a taste for earth that humans share with lots of other animals. |
| Her book, published in 2011 and now out in paperback, is full of both anecdote and analysis and covers both the wide phenomenon of eating earth — geophagy, which could include everything from tasting a mud pie as a child, or parent, to a craving for kaolin-rich clay from one spot and one spot only — the need that Sam’s store caters to. | Her book, published in 2011 and now out in paperback, is full of both anecdote and analysis and covers both the wide phenomenon of eating earth — geophagy, which could include everything from tasting a mud pie as a child, or parent, to a craving for kaolin-rich clay from one spot and one spot only — the need that Sam’s store caters to. |
| Both kinds of dirt-eating occur around the world. People on all the inhabited continents — more women and children than men, it seems, and more commonly during pregnancy — eat earth and the other substances Dr. Young mentions in her subtitle. | Both kinds of dirt-eating occur around the world. People on all the inhabited continents — more women and children than men, it seems, and more commonly during pregnancy — eat earth and the other substances Dr. Young mentions in her subtitle. |
| The practice goes back about two million years, according to one finding, and involves both medicinal and religious uses as well as the simple craving. | The practice goes back about two million years, according to one finding, and involves both medicinal and religious uses as well as the simple craving. |
| Dr. Young, a nutritional scientist at Cornell, first encountered pica (pronounced PYE-ka) on the island of Pemba, part of the Zanzibar archipelago. Sometimes the location of the clay is important, like the source of a wine. Take the terra sigillata from the Greek island of Lemnos, which Pliny wrote about in the first century. The island was a popular source of medicinal clay into the 20th century. A grotto in Bethlehem is another famous site. | Dr. Young, a nutritional scientist at Cornell, first encountered pica (pronounced PYE-ka) on the island of Pemba, part of the Zanzibar archipelago. Sometimes the location of the clay is important, like the source of a wine. Take the terra sigillata from the Greek island of Lemnos, which Pliny wrote about in the first century. The island was a popular source of medicinal clay into the 20th century. A grotto in Bethlehem is another famous site. |
| Most of these famous clays contain kaolin, once a main ingredient in Kaopectate (which now contains bismuth subsalicylate). Kaolin is definitely useful in combating diarrhea, and I’ve often wondered how people figured this out. | Most of these famous clays contain kaolin, once a main ingredient in Kaopectate (which now contains bismuth subsalicylate). Kaolin is definitely useful in combating diarrhea, and I’ve often wondered how people figured this out. |
| I imagined some early human, in extremis, on his or her hands and knees, looking down at the ground and thinking: “I could lie down and die, or I could eat some of this clay. Maybe it will plug me up.” | I imagined some early human, in extremis, on his or her hands and knees, looking down at the ground and thinking: “I could lie down and die, or I could eat some of this clay. Maybe it will plug me up.” |
| That may have happened, to someone, somewhere, at least once, but what I found in reading the book was that medicinal dirt eating probably started long before there were humans, let along humans with diarrhea. So our species might have picked up the habit from watching other animals, lots of which eat dirt. | That may have happened, to someone, somewhere, at least once, but what I found in reading the book was that medicinal dirt eating probably started long before there were humans, let along humans with diarrhea. So our species might have picked up the habit from watching other animals, lots of which eat dirt. |
| Amazonian parrots, for example, have specific “clay licks.” And as Dr. Young notes in her book, research by James Gilardi at the University of California, Davis, showed that the clay eaten by Amazonian parrots effectively prevents the birds from absorbing quinidine sulfate, a toxic substance found in the plants they eat. (Dr. Gilardi is now executive director of the World Parrot Trust.) | Amazonian parrots, for example, have specific “clay licks.” And as Dr. Young notes in her book, research by James Gilardi at the University of California, Davis, showed that the clay eaten by Amazonian parrots effectively prevents the birds from absorbing quinidine sulfate, a toxic substance found in the plants they eat. (Dr. Gilardi is now executive director of the World Parrot Trust.) |
| Baboons also eat dirt. And they seem to do so more when they are pregnant. The dirt they eat is high in clay, which, Dr. Young writes, protects the eater against toxic natural chemicals in food and also against bacteria and parasites, by lining the intestinal wall and grabbing on, chemically, to some of the toxins. | Baboons also eat dirt. And they seem to do so more when they are pregnant. The dirt they eat is high in clay, which, Dr. Young writes, protects the eater against toxic natural chemicals in food and also against bacteria and parasites, by lining the intestinal wall and grabbing on, chemically, to some of the toxins. |
| She offers a variety of examples of the value of clay, including a story of a condemned man in 16th-century England who acted as a guinea pig and took enough mercury to kill three men but combined it with wine laced with clay (with terra sigillata, in fact), and survived. Plain starch, like cornstarch, may also be protective. | She offers a variety of examples of the value of clay, including a story of a condemned man in 16th-century England who acted as a guinea pig and took enough mercury to kill three men but combined it with wine laced with clay (with terra sigillata, in fact), and survived. Plain starch, like cornstarch, may also be protective. |
| Adding to the plausibility of this idea is that pica is also more common among pregnant women, whose fetuses are more vulnerable to toxins than adults, and more common in the tropics, where pathogenic viruses and bacteria are more prevalent than in colder climes. | Adding to the plausibility of this idea is that pica is also more common among pregnant women, whose fetuses are more vulnerable to toxins than adults, and more common in the tropics, where pathogenic viruses and bacteria are more prevalent than in colder climes. |
| Dr. Young does not underestimate the power of culture. She told me that although protection might be a physiological driver for craving earth, depending on the cultural context a person might be more or less likely to actually end up eating dirt. The habit has often been scorned and condemned, among African slaves in America, for instance. | Dr. Young does not underestimate the power of culture. She told me that although protection might be a physiological driver for craving earth, depending on the cultural context a person might be more or less likely to actually end up eating dirt. The habit has often been scorned and condemned, among African slaves in America, for instance. |
| Studies continue, she said. Others have suggested that iron deficiency may play some role in craving earth. Chickens, it turns out, are a good model for human iron metabolism. They are easy to come by at Cornell, so she is involved in studying them. | Studies continue, she said. Others have suggested that iron deficiency may play some role in craving earth. Chickens, it turns out, are a good model for human iron metabolism. They are easy to come by at Cornell, so she is involved in studying them. |
| One thing is clear. Even though she offers an Internet source for white clay, Dr. Young does not recommend or endorse eating dirt or clay or any of the other substances that people might crave. | One thing is clear. Even though she offers an Internet source for white clay, Dr. Young does not recommend or endorse eating dirt or clay or any of the other substances that people might crave. |
| More research is needed, and dirt has its potential drawbacks, including bacteria, viruses, parasites and, depending on where it comes from, toxic chemicals that didn’t come from any plant. | More research is needed, and dirt has its potential drawbacks, including bacteria, viruses, parasites and, depending on where it comes from, toxic chemicals that didn’t come from any plant. |
| Dr. Young thus follows in the footsteps of my grandmother (and the grandmothers of many other people, I’m sure), who would say, “You have to eat a peck of dirt before you die,” but would never let you go out in the yard and gobble some up. | Dr. Young thus follows in the footsteps of my grandmother (and the grandmothers of many other people, I’m sure), who would say, “You have to eat a peck of dirt before you die,” but would never let you go out in the yard and gobble some up. |
This article has been revised to reflect the following correction: | This article has been revised to reflect the following correction: |
| Correction: July 10, 2013 | |
An | A review on Tuesday about “Craving Earth,” by Sera L. Young, misstated the surname of a researcher whose work at the University of California, Davis, looked at the protective effects of clay eaten by Amazonian parrots. He is James Gilardi, not Hilardi. |