Toward a Comprehensive Approach to the Collection and Analysis of Pica Substances, with Emphasis on Geophagic Materials

Abstract

BackgroundPica, the craving and subsequent consumption of non-food substances such as earth, charcoal, and raw starch, has been an enigma for more than 2000 years. Currently, there are little available data for testing major hypotheses about pica because of methodological limitations and lack of attention to the problem.MethodologyIn this paper we critically review procedures and guidelines for interviews and sample collection that are appropriate for a wide variety of pica substances. In addition, we outline methodologies for the physical, mineralogical, and chemical characterization of these substances, with particular focus on geophagic soils and clays. Many of these methods are standard procedures in anthropological, soil, or nutritional sciences, but have rarely or never been applied to the study of pica.Principal FindingsPhysical properties of geophagic materials including color, particle size distribution, consistency and dispersion/flocculation (coagulation) should be assessed by appropriate methods. Quantitative mineralogical analyses by X-ray diffraction should be made on bulk material as well as on separated clay fractions, and the various clay minerals should be characterized by a variety of supplementary tests. Concentrations of minerals should be determined using X-ray fluorescence for non-food substances and inductively coupled plasma–atomic emission spectroscopy for food-like substances. pH, salt content, cation exchange capacity, organic carbon content and labile forms of iron oxide should also be determined. Finally, analyses relating to biological interactions are recommended, including determination of the bioavailability of nutrients and other bioactive components from pica substances, as well as their detoxification capacities and parasitological profiles.SignificanceThis is the first review of appropriate methodologies for the study of human pica. The comprehensive and multi-disciplinary approach to the collection and analysis of pica substances detailed here is a necessary preliminary step to understanding the nutritional enigma of non-food consumption.

The relation between pica and iron deficiency in children in Zanjan, Islamic Republic of Iran: a case-control study

“…These findings differ from those of some other studies (3,19,23,24). But at least 2 double blind controlled studies did not find any relationship between iron therapy and pica behaviour (10).…”

“…The protection theory maintains that pica is a defensive practice that protects the gastrointestinal tract from absorbing pathogens and chemical substances. Although clay is an effective substance for this (3), more studies are needed to determine this relationship. A protective response to psychological stress is another theory proposed to explain pica (3).…”

“…Although clay is an effective substance for this (3), more studies are needed to determine this relationship. A protective response to psychological stress is another theory proposed to explain pica (3). The American Psychological Association believes that pica is a psychopathology that needs therapeutic interventions.…”

“…iron, zinc, selenium and calcium. There have been many studies on the validity of this hypothesis (1,3,5). According to this theory, the patients' taste towards the deficient material changes (3).…”

Mineralogical Profile of Geophagic Clayey Soils Sold in Selected South African Informal Markets

“…Thus, a deep red (5YR) on a Munsell colour chat is indicative of soils whose iron oxide mineral is hematite (Fe 2 O 3 ), while soils having goethite [FeO(OH)] as the main iron oxide mineral are yellowish brown (2.5YR-7.5YR). Soils containing lepidocrocite, another form of iron oxyhydroxide, are a distinctive orange colour (7.5YR) [23,24]. A previous study asserted that inclination for reddish or brownish soils is based on the supposition that such clays contain more iron [9].…”