Compositional Characteristics of Geophagic Clays in Parts of Southern Nigeria

  •  Okunlola OA    
  •  Owoyemi KA    


Geophagy is the practice of deliberate consumption of soil and clay deposits by humans, birds and other animalsin the wild. It is closely related to pica, a classified eating disorder characterized by abnormal cravings fornon-food items. The focus of this work is to determine the compositional characteristics of the geophagic claysconsumed around Asaba, Benin, Ibadan and Aramoko-Ekiti areas in southern Nigeria in order to get an insightinto the role these clay constituents play in geophagy. This study includes XRD aided mineralogicaldetermination, chemical analysis of major and trace elements using ICP-MS instrumentation, physical testsincluding determination of Atterberg limits. Biological parameters such as the bacteriological content andnutritional value were also determined from in situ samples of geophagic clays. X-ray diffraction analysis of tenrepresentative samples collected from these areas show mineralogical composition of predominantly kaolinitewith minor palygorskite, nontronite, illite, K-feldspar and halloysite, while the nonclay fraction is mainly quartz..The relatively high percentage of fine grained kaolinite content in the geophagic clays is similar to that inkaolinite-based western medicines that are marketed for the purpose of alleviating gastrointestinal upsets. Thischaracteristic is also revealed in the chemical analysis of the study samples which show average values of majorelements such Si02 (50.9%), Al2O3 (25.4%) and Fe2O3 (2.9%); while MgO, P2O5 and Ba are all below 0.5%. Thebacteriological analysis shows high total bacteria count of 9.8 x 104 – 11.4 x 104 cfu/gm for the Asaba sampleswhile the Benin and Aramoko-Ekiti samples have an average total bacterial count of 2.1 x 104. Cfu/gm TheIbadan samples have the lowest total bacteria count of 0.2 x 104. cfu/gm. The low total bacteria count of theIbadan sample may be due to the baking of the sample before consumption as against samples from Asaba,consumed fresh. Staphylococcus aureus and Micrococcus acidiophilus are the two micro-organisms common toall samples. Analysis for nutritional value indicates that geophagic clays have little or no nutritional value forhumans. Results of this study show that the rich kaolinite content of these clays could serve as an antacid, whilebacteriological and trace element content reveals the harmful effect of these clays on consumers.

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