Geophagy is the practice of eating clay, chalk and other forms of earth that are not generally considered part of a normal diet. Animals such as birds have been observed eating clay in various parts of the world. Humans also practice geophagy, sometimes because of malnutrition or as the result of a psychological condition called pica. Although it is possible to consume certain forms of earth with no ill effects, there still are health risks in doing so. In some instances, people willingly choose to practice geophagy and consider soil a valid culinary ingredient.
In the animal kingdom, different species have been witnessed eating chalk and clay. The exact purpose is not clear, but in some instances, it appears that the animals might be attempting to self-medicate themselves to relieve stomach pains. Other theories suggest that the animals ingest the earth to provide essential minerals that are not found in their typical diet.
In humans, there are several reasons that geophagy is practiced. One of the most studied causes is the psychological disorder called pica. Patients who suffer from pica have a compulsive urge to consume substances that are not commonly considered food or that have no nutritional value. A person with pica might eat earth, rocks, clay or even sand.
In nations where malnutrition is prevalent among the human population, soil and mud might be consumed out of necessity. There are some cultures in these countries that will mix mud with spices or sugar. The mud is then formed into cakes, dried in the sun and eaten as a meal.
Although there is evidence of geophagy existing in many places around the world, the danger to humans when ingesting earth can be significant. The clay or soil that is consumed could be contaminated with fecal matter from animals or sewage. There also are distinct forms of bacteria that exist naturally in the soil that can cause severe illness. One of the most immediate health threats from geophagy is intestinal blockage, a condition in which the ingested material forms a thick blockage in the digestive tract.
There is some archaeological evidence that geophagy occurred in prehistoric times. It has been theorized that humans developed prehistoric geophagy to absorb minerals that were required for survival but were not readily available in the standard diet. Another theory suggests that the consumed clays could have been part of early medicinal practices.
