Geophagia clay soil as a source of mineral nutrients and toxicants

Abstract

Geophagia, which involves ingestion of non-food lithospheric substances, is the major form of pica in many African cultures. A common lithospheric pica substance ingested in the Cape Three Point region of West Africa, particularly Ghana and Togo, is a white loamy clay soil. This clay soil is usually ingested by women of reproductive age. Some of the reasons assigned to clay geophagia include appealing flavour, to alleviate nausea during pregnancy, and for absorption of toxins in the gastrointestinal tract. Some speculation indicates that geophagia may be an attempt to replenish mineral nutrients in undernourished persons. The study of the acid extractable mineral contents of this white clay soil was done to provide information on the mineral contents that could potentially be absorbed in the gastrointestinal tract. Results showed that the clay soil was very dry with mean moisture content of 0.19±0.01%. On dry weight basis, the geophagia clay soil contained (mg/100 g) aluminium, 1,239.6; iron, 962.9; lead, 2.4; magnesium, 64.3; and zinc, 54.6. The extractable mineral contents of this clay soil, on dry weight basis, were (mg/100 g): zinc, 1.40±0.05; iron, 14.19±0.13; magnesium, 23.83±0.31; and aluminium, 37.91±2.94. Compared to the total minerals contents of the clay soil, the acid extractable fractions represented 2.6% of zinc, 1.5% of iron, 36.4% of magnesium, and 3.2% of aluminium. Even though lead was not detected in the acid extracts, a small amount was detected in the dry clay soil. Arsenic was not detected in any clay sample or extracts. It was concluded that the main mineral nutrient potentially contributed by this clay pica substance was iron. The clay soil liberated a substantial amount of iron (14.2 mg/100g), which constituted 78.9% of the 18 mg/d iron RDA for women of reproductive age and 53.0% of the 27 mg/day iron RDA for pregnant women. The potentially undesirable effect of ingesting this clay soil is the high level of aluminium (37.9 mg/100g).

Potential health risk assessment of toxic metals contamination in clay eaten as pica (geophagia) among pregnant women of Ho in the Volta Region of Ghana.

“…From our results, the levels of Arsenic obtained was below the mean exposure level of 3.0 µg/Kg BW/day set by the Joint FAO/WHO Expert Committee on Food Additives [31]. Tayie et al [10] reported 0.0 (nil) mg/Kg of Arsenic in clay samples in Accra were found to be lower than results obtained in this study. However, Nkansah et al [27] reported a range of 218-271 ppm from clay samples obtained from different parts of Kumasi Metropolis.…”

“…Lead concentrations were observed to be below the mean exposure levels and was in contrast with findings of range of values 549-622.92 µg/Kg reported by Nkansah et al [27]. In line with our results, Tayie et al [10] reported 2.36 ± 0.08 mg/100g. Lead consumption can result in adverse health effects such as the dysfunction of some vital organs such as kidneys, liver and heart.…”

“…Clay consumption is a common practice especially among women and is often linked with pregnancy, famine, idleness and insufficiency [8,9]. In Ghana, it is estimated that about 28% of women of reproductive age who practice geophagy, consume a daily average of 70g of clay [10]. Apparently, eating of clay and or soil as a habit was observed to be less frequent in boys than in girls.…”

Level of zinc in maize seeds and maize growing soils of central Mecha, Amhara National Regional State of Ethiopia

“…However, agricultural productivity has not reached its potential so far and people living in the area who depend on staple foods from their agriculture have paradoxically witnessed micronutrient defi-ciencies (a hidden hunger) due to the lack of nutrient dense quality foods (Melaku Umeta, 2003). (Mclean and Langille, 1976;Brennan et al, 1993;Srivastava et al, 1996;Shituu, 2013;Tayie et al, 2013). Distilled de-ionized water was used throughout the analysis.…”

Potential health risk assessment of toxic metals contamination in clay eaten as pica (geophagia) among pregnant women of Ho in the Volta Region of Ghana.

“…Table 3 shows the Permitted Daily Intake (PMTDI) of the heavy metals. To evaluate the risk of heavy metals from clay consumption at the extreme, we made the following assumptions in this research: the ingested dose was equal to the absorbed pollutant dose [25]; cooking (baking) has no effect on the pollutants [26]; the average adult body weight of Ghanaians was 60 kg [27]; Average daily consumption of clay in Ghana is 70 g clay per day [10]. Therefore, the EDI of heavy metals for adults was calculated as follows: See formula 1 in the supplementary files.…”