Most of us have never considered eating pies from the mud that we did when we were children, but for many people around the world, in a dinner of dirt there is nothing unusual. Now, the extensive meta-analysis that appeared in the journal of the Quarterly Review of Biology helps explain why this is so.

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

Sara Young, a researcher at Cornell University and lead author of the study, considered several hypotheses. Some researchers believe that geophysics is simply a consequence of a shortage of food. Others suggest that dirt is the source of missing nutrients, such as iron, zinc or calcium. Still others claim that the earth has a protective effect, working as a shield against parasites, pathogenic microorganisms and plant toxins.

In order to find the truth, Young and her colleagues analyzed the reports of missionaries, field doctors, researchers, anthropologists and collected a database of more than 480 cases of geophagy.

Researchers from Cornell found that the protective hypothesis corresponds to the best data. The database shows that geophagia is most often described in women at an early stage of pregnancy and in children at pre-adolescence. Both categories of people are particularly sensitive to parasites and pathogenic microorganisms. In addition, geophagia is the most common in the tropical climate, where food microbes are abundant. In addition, the database shows that people often eat the ground during episodes of gastrointestinal stress.

It is unlikely that intestinal problems are caused by dirt itself, because the type of clay that people usually eat gets deep from the earth, where pathogenic microorganisms and parasites do not exist. In addition, people tend to boil clay before eating.

Further research will be useful to confirm the protective hypothesis, the researchers say, but the available data at this point clearly distinguish it from others.

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