Pharmaco-Chemical Analysis and in Vivo Toxicity Assays of Edible Clays Mined in Nigeria and Consumed Globally

Abstract

Edible clays are consumed by diverse groups of people, especially of African descent, living in Africa and abroad, in a behavior known as geophagy. The clays are used topically as an emollient and drying agent and internally to control diarrhea. Scientific information concerning the chemical constituents and toxicity of edible clays is scarce. The aims of the present study, therefore, were to ascertain the chemical composition of white edible clays (WEC) and gray edible clays (GEC); to determine their toxicity profiles using analytical chemical methods; to test the acute and sub-acute toxicity of edible clays in their natural form as consumed; and to compare the raw and processed clays, and also to compare the latter to a proprietary drug known as ‘Mist kaolin’ (Moko®) which contains some clay along with other chemicals. Atomic absorption spectroscopy (AAS) and gas chromatography/mass spectrometry (GC/MS) were used to determine the elements present. White female Wistar mice and rats were used for the acute and sub-acute toxicity analyses, respectively. The results from AAS showed the presence of heavy metals and metalloids in both GEC and WEC, and the GC/MS revealed the presence of contaminants such as indomethacin and ethyl benzene, but quantities were below human toxicity levels. Doses of 100–500 mg/kg of either clay type could be harmful to the digestive system, but all of the tests revealed that edible clay is not toxic to humans unless very large amounts (500–1000 mg/kg of body weight) are consumed.

Prevalence of and risk factors for iron deficiency among pregnant women with moderate or severe anaemia in Nigeria: a cross-sectional study

“…Edible kaolin clay is obtained from earth and contains kaolinite which prevents proper absorption of iron from the duodenum and might thus cause iron deficiency if consumed frequently [48]. Edible kaolin clay has been found to contain chemicals and heavy metals such as arsenic, lead, nickel, silicon, mercury, cadmium, anthraquinone, small amount of androgens and steroids, and some micro-organisms [61][62][63]. It will be beneficial to explore further the association between edible kaolin clay and IDA to determine if the association is a cause or an effect of IDA as earlier studies have given conflicting reports [48,64].…”