My answer to Why do people with anemia tend to have Pagophagia?
Answer by Connie b. Dellobuono:
Folk wisdom (and some early investigators) maintained that pica reflected an appetite to compensate for nutritional deficiencies, such as low iron or zinc. Some forms of pica (as in pregnant women who are iron deficient) can be treated by supplementing the nutrient.
Later research has demonstrated that the substances ingested generally do not provide the mineral or nutrient in which patients are deficient. As the people start eating nonfoods, pica can also cause the nutritional deficiencies with which it is associated.
In one case study, pagophagia was reported to cause iron deficiency anemia. At the same time, however, the researchers suggested that chewing ice may benefit stomatitis and glossitis.
The nutrients obtained from nonfoods such as soil or ice will vary widely depending on geographic location. For example, ice made from hard water will contain more minerals, especially calcium and magnesium, but simply drinking the water will provide the same minerals.