Nearly everyone gets food cravings from time to time. Pregnant women are famous for their midnight yearnings for pickles and ice cream. And the desire for chocolate is the stuff of legend.
It's tempting to believe -- as many people do -- that cravings are the body's way of telling us we're lacking a certain nutrient that the food we crave can supply. Chocolate, the belief goes, might soothe a broken heart by replacing compounds lost in oceans of tears. Pregnant women might crave ice cream because they need calcium, or pickles because they lack sodium.
Pregnant women rarely crave fruits and vegetables. More often, they yearn for foods that are very sweet, spicy or salty. From an evolutionary standpoint, this makes sense. A craving for highly palatable foods may have been nature's way of boosting calorie intake, ensuring a healthy pregnancy.
But other kinds of craving make a lot less sense at face value. Some people, for example, get hankerings for things that aren't really considered foods at all -- such as ice, chalk or cornstarch.
The desire to eat non-food items is called pica -- from the Latin word for magpie, a bird known for its indiscriminate feeding habits. Pica is a complicated condition because there are both cultural and nutritional issues associated with it.
In some cultures -- both inside and outside the United States -- it is not uncommon for women to consume clay or dirt during pregnancy. In the Deep South, some people believed that it would relieve the nausea that comes with morning sickness. In some cultures (in Kenya and Uganda, for example) earth-eating, or geophagia, may also have ceremonial or religious purposes.
But there are also numerous case reports of pica that were associated with mineral deficiencies -- especially of iron, and possibly zinc. Iron deficiency is not uncommon in women of childbearing age, particularly during pregnancy.
Because of these various contributing factors, there has been a longstanding debate in nutrition research over the relationship between pica and nutrient status. Some argue that pica \o7causes \f7a nutrient deficit: Eating several cups of cornstarch at a sitting, for example, could bind up dietary iron, making it unavailable to the body. But others argue (and most evidence suggests) that pica frequently is\o7 caused\f7 by a deficit -- specifically, of iron.
