Featured Research

from universities, journals, and other organizations

Eating dirt can be good for the belly, researchers find

Date:
June 4, 2011
Source:
University of Chicago Press Journals
Summary:
Most of us never considered eating the mud pies we made as kids, but for many people all over the world, dining on dirt is nothing out of the ordinary. Now an extensive meta-analysis helps explain why.

Most of us never considered eating the mud pies we made as kids, but for many people all over the world, dining on dirt is nothing out of the ordinary. Now an extensive meta-analysis forthcoming in the June issue of The Quarterly Review of Biology helps explain why.

Related Articles


According to the research, the most probable explanation for human geophagy -- the eating of earth -- is that it protects the stomach against toxins, parasites, and pathogens.

The first written account of human geophagy comes from Hippocrates more than 2,000 years ago, says Sera Young, a researcher at Cornell University and the study's lead author. Since then, the eating of earth has been reported on every inhabited continent and in almost every country.

Despite its ubiquity, scientists up to now have been unable to definitively explain why people crave earth. Several hypotheses had been considered plausible. Some researchers think geophagy is simply a consequence of food shortage. In other words, people eat dirt to ease the pangs of hunger, even though it doesn't provide any nutritional value. Others have suggested that nutrition is exactly why dirt is consumed; perhaps people crave dirt because it provides nutrients they lack, such as iron, zinc, or calcium. Still others posit that earth has a protective effect, working as a shield against ingested parasites, pathogens, and plant toxins.

To sort through the possible explanations, Young and her colleagues analyzed reports from missionaries, plantation doctors, explorers, and anthropologists to put together 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 could then use patterns in the data to evaluate each potential explanation.

They found the hunger hypothesis unlikely. Studies in the database indicate that geophagy is common even when food is plentiful. Moreover, when people eat dirt they tend to eat only small quantities that are unlikely to fill an empty stomach.

The nutrition hypothesis was also a poor fit to the data. The database shows that the kind of earth people eat most often is a type of clay that contains low amounts of nutrients like iron, zinc, and calcium. Plus, if calcium deficiency drove people to eat dirt, one would expect them to do it most often at life stages when they need calcium the most -- adolescence or old age. But that isn't the case, according to the database. Reports do indicate that geophagy is often associated with anemia, but several studies have shown that cravings for earth continue even after people are given iron supplements. What's more, some research suggests that clay can bind to nutrients in the stomach, making them hard to digest. If that's true, it's not a lack of nutrients that causes geophagy; rather it could be the other way around.

Overall, the protection hypothesis fits the data best, the Cornell researchers found. The database shows that geophagy is documented most commonly in women in the early stages of pregnancy and in pre-adolescent children. Both categories of people are especially sensitive to parasites and pathogens, according to Young and her colleagues. In addition, geophagy is most common in tropical climates where foodborne microbes are abundant. Finally, the database shows that people often eat earth during episodes of gastrointestinal stress. It's unlikely the intestinal problems are caused by the dirt itself because the type of clay people usually eat comes from deep in the ground, where pathogens and parasites are unlikely to contaminate it. Plus, people usually boil the clay before eating it.

More study would be helpful to confirm the protection hypothesis, the researchers say, but the available data at this point clearly support it over the other explanations.

"We hope this paper stimulates [more] research," Young and her colleagues write. "More importantly, we hope readers agree that it is time to stop regarding geophagy as a bizarre, non-adaptive gustatory mistake."

"With these data, it is clear that geophagy is a widespread behavior in humans … that occurs during both vulnerable life stages and when facing ecological conditions that require protection."

Young has also released a book on the subject called Craving Earth: Understanding Pica -- the Urge to Eat Clay, Starch, Ice, and Chalk.


Story Source:

The above story is based on materials provided by University of Chicago Press Journals. Note: Materials may be edited for content and length.


Journal Reference:

  1. Sera L. Young, Paul W. Sherman, Julius Beau Lucks, and Gretel H. Pelto. Why on Earth?: Evaluating Hypotheses about the Physiological Functions of Human Geophagy. The Quarterly Review of Biology, 2011; 86: 2

Cite This Page:

University of Chicago Press Journals. "Eating dirt can be good for the belly, researchers find." ScienceDaily. ScienceDaily, 4 June 2011. <www.sciencedaily.com/releases/2011/06/110602162820.htm>.
University of Chicago Press Journals. (2011, June 4). Eating dirt can be good for the belly, researchers find. ScienceDaily. Retrieved October 26, 2014 from www.sciencedaily.com/releases/2011/06/110602162820.htm
University of Chicago Press Journals. "Eating dirt can be good for the belly, researchers find." ScienceDaily. www.sciencedaily.com/releases/2011/06/110602162820.htm (accessed October 26, 2014).

Share This



More Health & Medicine News

Sunday, October 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Texas Nurse Nina Pham Cured of Ebola

Texas Nurse Nina Pham Cured of Ebola

AFP (Oct. 25, 2014) — An American nurse who contracted Ebola while caring for a Liberian patient in Texas has been declared free of the virus and will leave the hospital. Duration: 01:01 Video provided by AFP
Powered by NewsLook.com
Toxin-Packed Stem Cells Used To Kill Cancer

Toxin-Packed Stem Cells Used To Kill Cancer

Newsy (Oct. 25, 2014) — A Harvard University Research Team created genetically engineered stem cells that are able to kill cancer cells, while leaving other cells unharmed. Video provided by Newsy
Powered by NewsLook.com
IKEA Desk Converts From Standing to Sitting With One Button

IKEA Desk Converts From Standing to Sitting With One Button

Buzz60 (Oct. 24, 2014) — IKEA is out with a new convertible desk that can convert from a sitting desk to a standing one with just the push of a button. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com
Ebola Protective Suits Being Made in China

Ebola Protective Suits Being Made in China

AFP (Oct. 24, 2014) — A factory in China is busy making Ebola protective suits for healthcare workers and others fighting the spread of the virus. Duration: 00:38 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins