Occasionally, there are news stories about a man who eats steel or a girl who likes to eat plastic. Such a condition where the person develops an appetite for a non-food substance is called pica. Pica is more common than one would think. The most common cases are those of dirt, clay and chalk, with the disorder being much more prevalent in children or pregnant women. Although pica is officially a mental disorder (possibly related to OCD), it is possible that it is a neurological mechanism to cure a certain mineral deficiency. For example, patients with coeliac diseases or hookworm infections tend to be iron-deficient and the substances they eat tend to contain iron. It is unclear how the brain knows what “food” to eat to cure a disease, but there are many cases where people subconsciously consume foods that would improve their health. According to a study, between 8% and 65% of people have had a sudden urge for a very strange appetite. However, as substances commonly involved in pica (such as dirt and ice) are solids, they can damage the oesophagus and the digestive tract. Also, they may contain toxic chemicals which can cause poisonings, making pica a potentially dangerous condition.