Last week, Sera Young, author of Craving Earth: Understanding Pica–the Urge to Eat Clay, Starch, Ice, and Chalk was interviewed on Living Earth about the book.

Below are some excerpts from the interview. You might also want to visit the Facebook page for Living on Earth which includes listeners experience with eating dirt and pica.

GELLERMAN: So, why do people eat dirt?

YOUNG: That’s a very good question and it’s one I’ve been studying for the last decade or so. There are a number of explanations, and what we’ve found is that the best one, the one that fits the most of the observations that we’ve made is that it’s a protective behavior. So, clay is a big component of the earth that’s eaten. And clay is really good at binding, it almost acts as like a mud mask for your face, except it’s a mud mask for your gut in a way. It sucks up these pathogens like viruses and bacteria and harmful chemicals and lets them evacuate from your body without entering your bloodstream.

GELLERMAN: There’s something in the dirt that protects us?

YOUNG: Exactly. And what’s so, sort of, paradoxical about what we’ve found is that dirt can in fact be cleansing. People are really selective about the dirt that they eat. It’s not just any dirt, and the dirt that’s preferred is, well, often described as ‘clean dirt’. And it’s also very clay-rich, so what you find is very soft, malleable, it’s not like the sand you find at the beach, or the black humus-y kind of soil that you’d like to plant your tomatoes in.

GELLERMAN: I have a bag of dirt that we got from Sam’s General Store in White Plains, Georgia. It’s called ‘Grandma’s Georgia White Dirt’ and I just got it – it says: Not intended for human consumption, but I’m going to try it anyhow…

[BAG RUSTLING]

YOUNG: (Laughs).

GELLERMAN: It looks like chalk and it feels slippery…ooh it is… and it gets all over my hands.

[CHEWING DIRT]

GELLERMAN: It crumbles….yeah, it tastes like chalk, clean chalk.

GELLERMAN: Well, the word pica comes from the word magpie, which is a bird.

YOUNG: Right. It’s a bird that was thought to have an indiscriminate appetite because it builds its nest will all of these sort of found objects. And so, in the early, I think it was the early 1300s, this name was given to the phenomenon of women, of pregnant women typically, who were craving all of these non-food substances.

But, with the case of the bird, it was a misnomer, they weren’t eating these things – they were building their nests with them. And in the case of the pica phenomenon in humans, it’s also a misnomer because people are not indiscriminate at all – people have extremely, extremely specific cravings.

GELLERMAN: So what is it about pregnant women?

YOUNG: Pregnant women’s behavior is easily dismissed because pregnant women: they know not what they do. But in fact, they’re immuno-compromised. Which means that their immune system is tamped down to avoid rejecting the fetus or the embryo, and at the same time they really need to be shielding this very vulnerable thing growing in them from insults – including pathogens like viruses and bacteria and other harmful chemicals.

So, people with rapidly dividing cells such as pregnant women and also young children are at greatest risk, or in most need of protection. Geophagy is a protective behavior. It fits with our hypothesis because in fact it is pregnant women and young children who do this most frequently.