8. Pica
People with Pica have a compulsive desire to eat non-food items. This includes things such as paper, metal, glue and even dirt. The above image shows a collection of metal items removed from the stomach of one sufferer. Although there is no real consensus of the cause of the disease, some experts think that, bizarrely, it could be caused by a mineral deficiency. Often the substance that the sufferers are compelled to eat contain the mineral they're deficient in. Those with Pica for things such as dirt, clay or wood are often found to have an iron or zinc deficiency. As well as a physical deficiency, it has also been proposed as a possible symptom of mental illnesses such as OCD. There is also a widespread practice in the American state of Georgia in which locals regularly chow down on a white clay called kaolin. This is so popular that kaolin is sold in convenience stores as a "novelty item", but it's still unclear as to exactly why people want to chew on dirt so much. Due to the uncertainty about the causes of Pica, there's no definitive way to cure it. The best we can hope for is to limit any potentially dangerous pica cravings.