Human Geophagia, Calabash Chalk and Undongo: Mineral Element Nutritional Implications Peter W. Abrahams 1 *, Theo C. Davies 2¤ , Abiye O. Solomon 2 , Amanda J. Trow 1 , Joanna Wragg 3 1 Institute of Geography and Earth Sciences, Aberystwyth University, Ceredigion, United Kingdom, 2 Department of Geology and Mining, University of Jos, Jos, Nigeria, 3 British Geological Survey, Keyworth, Nottingham, United Kingdom Abstract The prime aim of our work is to report and comment on the bioaccessible concentrations – i.e., the soluble content of chemical elements in the gastrointestinal environment that is available for absorption – of a number of essential mineral nutrients and potentially harmful elements (PHEs) associated with the deliberate ingestion of African geophagical materials, namely Calabash chalk and Undongo. The pseudo-total concentrations of 13 mineral nutrients/PHEs were quantified following a nitric-perchloric acid digestion of nine different Calabash chalk samples, and bioaccessible contents of eight of these chemical elements were determined in simulated saliva/gastric and intestinal solutions obtained via use of the Fed ORganic Estimation human Simulation Test (FOREhST) in vitro procedure. The Calabash chalk pseudo-total content of the chemical elements is often below what may be regarded as average for soils/shales, and no concentration is excessively high. The in vitro leachate solutions had concentrations that were often lower than those of the blanks used in our experimental procedure, indicative of effective adsorption: lead, a PHE about which concern has been previously raised in connection with the consumption of Calabash chalk, was one such chemical element where this was evident. However, some concentrations in the leachate solutions are suggestive that Calabash chalk can be a source of chemical elements to humans in bioaccessible form, although generally the materials appear to be only a modest supplier: this applies even to iron, a mineral nutrient that has often been linked to the benefits of geophagia in previous academic literature. Our investigations indicate that at the reported rates of ingestion, Calabash chalk on the whole is not an important source of mineral nutrients or PHEs to humans. Similarly, although Undongo contains elevated pseudo-total concentrations of chromium and nickel, this soil is not a significant source to humans for any of the bioaccessible elements investigated. Citation: Abrahams PW, Davies TC, Solomon AO, Trow AJ, Wragg J (2013) Human Geophagia, Calabash Chalk and Undongo: Mineral Element Nutritional Implications. PLoS ONE 8(1): e53304. doi:10.1371/journal.pone.0053304 Editor: Andrea S. Wiley, Indiana University, United States of America Received July 27, 2012; Accepted November 30, 2012; Published January 7, 2013 Copyright: ß 2013 Abrahams et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The authors have no support or funding to report. Competing Interests: The authors have declared that no competing interests exist. * E-mail: pwa@aber.ac.uk ¤ Current address: Department of Mining and Environmental Geology, University of Venda, Thohoyandou, South Africa Introduction Humans ingest soil both deliberately – a practice known as geophagia or geophagy – and accidentally, with consequent implications to their mineral nutrition [1]. Thus following the encounter with digestive fluids, chemical elements can be solubilised from soils and are potentially available for absorption, the so-called bioaccessible soil content. For example, geophagical soils consumed by ethnic Bengali communities in the UK were found by Abrahams et al. [2] to be a significant source of bioaccessible iron (Fe). Since this chemical element is an important mineral micronutrient with Fe deficiency being widespread throughout the world [3], the consumption may be of benefit to the geophagist although with the quantities of soil that can be deliberately consumed (e.g., up to c. 65 g/day [2]; 8–108 g/day with a median of 28 g/day [4]; 2.5–219 g/day with a median of 41.5 g/day [5]) so-called Guidance Levels [6] could be exceeded. Furthermore, Abrahams et al. [2] highlighted the risk of soil-lead (Pb) toxicity affecting pregnant women – a group of human society who are especially associated with geophagia – and their foetus. Conversely, the absorption of elements into the human body following soil consumption can also be reduced attributable to, for example, the adsorptive properties of ingested earth materials that can lower bioaccessible concentrations. Hooda et al. [7] indicated the sorption potential of some geophagical soils in lowering the bioaccessibility of copper (Cu), Fe and zinc (Zn), although other materials were identified to be a source of calcium (Ca), magnesium (Mg) and manganese (Mn) that humans could potentially utilise. A review of the literature clearly indicates that geophagia is not limited to any particular age group, race, sex, geographic region or time period, though today the practice is most obviously common amongst the world’s poorer or more tribally-oriented people and is, therefore, particularly extensive in the tropics [8]. A number of accounts relating to geophagia in Nigeria can be found in the literature [9–13], and here the practice is noted to be especially associated with pregnant women who consume earth materials to alleviate the symptoms of morning sickness. Calabash chalk – also known (according to language/locality) as Argile, Calabar stone, Calabash clay, Ebumba, La Craie, Mabele, Ndom, Nzu, Poto and Ulo – is a generic term used for naming these Nigerian geophagical materials. The migration of people from societies where geophagia is especially prevalent results in a cultural transfer of the practice to PLOS ONE | www.plosone.org 1 January 2013 | Volume 8 | Issue 1 | e53304