Geophagy among school children in Western Kenya

Geissler, Paul Wenzel; Mwaniki, Dennis; Thiong'o, F; Friis, Henrik

doi:10.1046/j.1365-3156.1997.d01-345.x

Cited by 76 publications

(40 citation statements)

References 12 publications

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“…Some researchers have asked informants to demonstrate how much they ate using pre-collected soil if it was not possible to have pica substances at the interview [84], [85]. A similar approach may be used with starch, uncooked rice, etc.…”

Section: Resultsmentioning

confidence: 99%

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

Young

Wilson²,

Miller

et al. 2008

PLoS ONE

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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.

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Section: Resultsmentioning

confidence: 99%

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

Young

Wilson²,

Miller

et al. 2008

PLoS ONE

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“…(The intake was estimated in a subsample of 39 geophageous children. For details on soil types and amounts and estimated daily ingestion see Geissler et al 1997).…”

Section: Resultsmentioning

confidence: 99%

Geophagy, iron status and anaemia among primary school children in Western Kenya

Geissler

Mwaniki

Thiong'o

et al. 1998

Tropical Med Int Health

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SummaryAs part of a cross-sectional study among 156 primary school children (median age 13 years, range 10᎐18) in Western Kenya, geophagy was assessed through interviews. 114 (73.1%) of these children reported eating soil daily. Haemoglobin levels were determined in all 156 children and serum ferritin concentrations in 135. The mean haemoglobin (Hb) concentration was 12.7 g/dl, and median ferritin concentration 27.2 g/l. Both the proportion of anaemic (Hb Ͻ 11.0 g/dl) and of iron-depleted (ferritin Ͻ 12 g/l) children was significantly higher among the geophageous children than among the nongeophageous (9.6% vs. 0% anaemia; P ϭ 0.037; 18.4% vs. 5.4% iron depletion; P ϭ 0.046). Serum ferritin and haemoglobin concentrations were not correlated (r ϭ 0. 13 5; P ϭ 0. 100). Multiple regression analysis showed that geophagy, hookworm eggs per gram faeces and malaria parasite counts per l blood were independent predictors of serum ferritin, when controlling for other helminth infections, age and sex, and socio-economic and educational background of the children's families and family size (y ϭ 36.038᎐11.247(geophagy) ᎐ 0.010(hookworm epg) ϩ 0.001(malaria parasite counts); R 2 ϭ 0.17). Multiple regression analysis with haemoglobin as dependent variable and the same independent variables did not reveal any significant predictors. Analysis of the soil eaten by the children revealed a mean HCl-extractable iron content of 168.9 mg/kg (SD 44.9). Based on the data on the amounts eaten daily and this mean iron content, soil could provide on average 4.7 mg iron to a geophageous child (interquartile range 2.1᎐7.1 mg), which is equivalent to 32% of the Recommended Nutrient Intake (RNI) for girls (interquartile range 14᎐48%) or 42% of the RNI for boys (interquartile range 19᎐63%). Iron depletion and anaemia are associated with geophagy, but only serum ferritin concentrations were shown to be dependent upon geophagy in the regression model. From the cross-sectional data no inference about causality can be made. To clarify the possible causal relationships involved, longitudinal studies and iron-supplementation intervention studies are needed.

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“…Although this amount exceeds the US Environmental Protection Agency's 200·mg·day -1 risk-assessment level for involuntary soil ingestion (Stanek and Calabrese, 1995), it is within the daily range of human consumption reported by Simon (1998). For example, children in western Kenya consume an average of 28·g of soil daily, ranging from 8 to 108·g (Geissler et al, 1997).…”

Section: Digestion Trialsmentioning

confidence: 99%

Adaptive function of soil consumption: anin vitrostudy modeling the human stomach and small intestine

Dominy

Davoust

Minekus

2004

Journal of Experimental Biology

104

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Despite occurring in a wide variety of taxa, deliberate soil consumption (geophagy) is a poorly understood behavior. In humans, geophagy is sometimes considered aberrant or a sign of metabolic dysfunction. However, geophagy is normally assigned an adaptive function in nonhuman primates and various other organisms. One hypothesis submits that clay-rich soil adsorbs intestinal insults, namely plant metabolites or diarrhoea-causing enterotoxins. Here we test the capacity of kaolin, a commonly ingested clay, to adsorb quinine (an alkaloid) and two types of tannin (digestion-inhibitors). Trials were conducted in vitro using the TNO Intestinal Model, a device that closely simulates digestion by the human stomach and small intestine. Kaolin reduced the bioavailability of each compound by ≤30%. However, because we could not replicate clay-epithelial adhesion and reduced motility, these results may underestimate adsorption in vivo. We also show that kaolin fails to render calcium oxalate soluble. We conclude that gastrointestinal adsorption is the most plausible function of human geophagy. Adaptive advantages include greater exploitation of marginal plant foods and reduced energetic costs of diarrhoea, factors that could account for the high frequency of geophagy in children and pregnant women across the tropics. Movies available on-line

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Geophagy among school children in Western Kenya

Cited by 76 publications

References 12 publications

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

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

Geophagy, iron status and anaemia among primary school children in Western Kenya

Adaptive function of soil consumption: anin vitrostudy modeling the human stomach and small intestine

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