Pica, or the practice of eating dirt or clay, is comparatively common. Many people feel that a clay bar (about twice the size of a candy bar) once a week can relieve irritability, constipation, mineral deficiencies and heart burn. There is some evidence that this might, in fact, be true.
Pregnant women (all over the world) have been known to have intense cravings for dirt. However, most dirt is contaminated with paint chips, which are made of lead. When the blood of a group of such women was tested it was found that they had mild mineral deficiencies (compared to the women with no cravings). Still none of these studies are conclusive, and there are many complications that can arise from eating too much dirt or contaminated dirt. So you probably don’t need to go out and get yourself a handful just yet.