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Weird Science: Eating Dirt Can Be Good For You

A member of a farming cooperative plants tomatoes on his farm near Yauco, Puerto Rico.
A member of a farming cooperative plants tomatoes on his farm near Yauco, Puerto Rico.
Jack Delano / Courtesy of The Library of Congress

Eating dirt? It sounds like one of the tamer though still disgusting episodes of TLC's Addicted, the awful show (awful in a "can't stop watching" kind of way) that made words like "interventionist" part of the common lingo. Geoophagy, however, isn't just a harmful medical disorder. It may actually protect the stomach against toxins, parasites and pathogens, according to an article in the June issue of The Quarterly Review of Biology.

Sera Young, the study's lead author and a researcher at Cornell University, analyzed reports from missionaries, plantation doctors, explorers and anthropologists to compile a database of more than 480 cultural accounts of geophagy. The database includes as many details as possible about the circumstances under which earth was consumed and by whom.

The researchers examined the data patterns and soon discounted the two main hypotheses about the cause of dirt-eating. They found the hunger hypothesis unlikely, since geophagy is common even when food is plentiful. Moreover, people tend to eat dirt only in small quantities that wouldn't sate an empty belly.

The other main theory, that people eat dirt because of nutrient deficiencies also seemed implausible, since people mostly eat a type of clay that contains low amounts of iron, zinc, and calcium.

Young and her colleagues concluded that the most likely explanation was the protection hypothesis: People eat dirt to protect against stomach parasites and pathogens.

Their reasoning? Geophagy is highest among women in the early stages of pregnancy and in pre-adolescent children, two groups of people who are especially sensitive to parasites and pathogens. It is most common in tropical climates where foodborne microbes are abundant, and it mostly occurs during episodes of gastrointestinal stress. Could the intestinal problems be the result of the dirt itself? Young thinks that's unlikely because the type of clay people usually eat comes from deep in the ground, where pathogens and parasites are unlikely to contaminate it. Also, people usual boil the clay before eating it.

The eating of earth has been reported in almost every country, with the first written account of human geophagy coming from Hippocrates over 2,000 years ago. These

results cast a new light on the widespread but poorly understood behavior.

Young is also the author of a book, Craving Earth: Understanding Pica--the Urge to Eat Clay, Starch, Ice, and Chalk.


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