Clay Craving and Dirt Dining: Eating Earth May Be Good for Us

Clay Craving and Dirt Dining: Eating Earth May Be Good for Us

Rachel Nuwer
Published: 06/06/2011

Clay ripe for eating from Zanzibar. Credit Sera Young. 

In the deep south of the U.S., the smell of a fresh dirt road on a humid summer day is enough to trigger some locals’ mouth to watering. Shugana Williams, an archivist and librarian at the University of Southern Mississippi Gulf Coast, recalls sitting around the fireplace as a little girl in Laurel, Mississippi, while the old folks baked freshly dug earth in aluminum containers. “They’d just sit there and eat it,” she says, “a red dirt, as they called it.” Both of her parents, born in the 1940s, eat dirt to this day. Williams’ father spoke of his mother and sisters consuming earth when he was growing up in Alabama, and Williams’ mother says her own grandmother and mother partook in the practice in Mississippi. “It’s really a heavily traditional thing that they do,” Williams says.
They aren’t alone. People across the globe have practiced dirt eating—or geophagy—for millennia. Geophagy is a type of pica, or the purposeful consumption of non-food items like ice, earth, or uncooked starches like rice. The first reference dates back more than 2000 years to Hippocrates, but archaeological evidence suggest the practice is thousands of years older, still.
Yet despite geophagy’s long history, researchers are only now discovering what drives the cravings. In some cases, at least, earth eating may protect the diner from toxins, parasites, and pathogens—contrary to some previous assumptions that geophagy arises because people either have nothing else to eat or because soil contains nutrients they lack.
Sera Young, a nutritional anthropologist at Cornell University, compiled 480 records—all that she could find—referencing the behavior. They extended from 2,000 years ago to the year 2010, from infants to the elderly, and from the arctic to the tropics. She turned up records of geophagy in David Livingstone’s accounts of east Africa, in slave plantation records, from Jefferson Davis’ wife’s writings, and in scribblings of Siberian anthropologists. Young found geophagy seemed most often referenced in women, especially those who were pregnant, and also in pre-adolescent children and people suffering from gastrointestinal stress.

Distributions of geophagy around the world. The darker the country, the more common the practice, according to Young's findings. The darkest countries, like the U.S., have more than seven accounts of populations engaging in dirt eating.  Credit S. Young et. al.
Young explains the paradoxical idea of dirt as a cleansing substance in an article published in The Quarterly Review of Biology. Clay, the dirt of choice for most geophagists, binds to toxins and pathogens like bacteria and parasites. It’s sticky, so it also forms a layer over the mucus lining between the gut and the blood stream, reducing the digestive organs’ permeability that could otherwise allow harmful substances entry into the body. Clay is often used to prepare foods known to be dangerous: aborigines in Australia use it when cooking a tuber that causes diarrhea if eaten raw, and in the Andes, clay is used to protect against Andean potatoes that contain glycoalkaloids, a potent toxin. And humans aren’t the only ones who engage in this behavior. Especially in tropical areas, primates and birds often eat dirt, probably to detoxify harmful plants they munched on.

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