I watched her from the kitchen window. Clawing away at the crusty anthill in the backyard. She cupped the red earth in her hand and threw it into the back of her mouth. She chewed, sucked, and then swallowed, satisfied.  I was twelve years old and growing up in Zambia. I had a western upbringing which convinced me my pregnant aunt was indulging in some occult behaviour. But now I am older and wiser or at least more knowledgeable and know the name of this practice – geophagia: “the practice of eating earthy or soil-like substances such as clay, and chalk.” Depending on who you ask, it can be considered an eating disorder, a culturally acceptable practice, or a response to famine. It is common in parts of Africa, India, and southern parts of USA. It was first documented in medicine in 370 BC in ancient Greece and Rome by Hippocrates:

“If a pregnant woman feels the desire to eat earth or charcoal and then eats them, the child will show signs of these things.”

Geophagia is also common in the animal kingdom and is well documented in birds. Scientists speculate this behaviour confers an evolutionary advantage.  However, despite human beings from Homo habilis to Homo sapien eating dirt for over two millions years the benefits and harms are still much debated.

Eating soil-substances may provide essential nutrients like sulphur and phosphorous. For pregnant women in India and Africa, fine red clay may diminish nausea possibly by coating the gut and absorbing toxins.  Clay eating during pregnancy may also provide supplemental calcium, the demand for which increases during pregnancy to form the fetal skeleton.  It has also been associated with iron-deficiency anaemia and pica, a medical disorder characterised by persistent and compulsive cravings to eat non-food items e.g. clay, soap, mucus, ash. During a famine, eating earth may suppress the appetite and fill the stomach which ironically has also been observed in people suffering from anorexia. In South Africa, it has been used for a rather interesting purpose – to lighten the skin (which supposedly these black women think makes them more attractive). In Haiti, they go as far as working the clay mud into a “bon bon de terre” (Earthy treats) that unfortunately have little nutritional value and are associated with health problems.  In America and Italy, clay was added to acorn bread to reduce the toxicity of tannins in acorns, as well as to improve the overall nutrient value of the bread.

There are some risks to eating earth, for example consumption of contaminated soil, intestinal obstruction, and ingestion of harmful parasites. Children are particularly susceptible to worm infestations. Europe long ago did away with this practice but in Africa, it is still thriving in villages and in cities, or at least where you can find a tree or anthill with doti (dirt). Despite the possible side effects, my pregnant aunty was less irritable and less queasy after her indulgence. She also gave birth to a healthy, happy boy.

Muza Gondwe is a science communicator from Malawi who is keen to engage Africans with science. She is currently on a fellowship at the Centre of African Studies on the Public Understanding of Science in Africa, working on a project titled African Science Heroes.