Evaluation of geochemical characteristics of some geophagic clays, southern Nigeria

1 23

Environmental Geochemistry andHealthOfficial Journal of the Society forEnvironmental Geochemistry andHealth ISSN 0269-4042 Environ Geochem HealthDOI 10.1007/s10653-014-9619-2

Evaluation of geochemical characteristicsand health effects of some geophagic clayssouthern Nigeria

A. S. Olatunji, J. O. Olajide-Kayode &A. F. Abimbola

1 23

Your article is protected by copyright and all

rights are held exclusively by Springer Science

+Business Media Dordrecht. This e-offprint

is for personal use only and shall not be self-

archived in electronic repositories. If you wish

to self-archive your article, please use the

accepted manuscript version for posting on

your own website. You may further deposit

the accepted manuscript version in any

repository, provided it is only made publicly

available 12 months after official publication

or later and provided acknowledgement is

given to the original source of publication

and a link is inserted to the published article

on Springer's website. The link must be

accompanied by the following text: "The final

publication is available at link.springer.com”.

ORIGINAL PAPER

Evaluation of geochemical characteristics and health effectsof some geophagic clays southern Nigeria

A. S. Olatunji • J. O. Olajide-Kayode •

A. F. Abimbola

Received: 23 December 2013 / Accepted: 25 April 2014

� Springer Science+Business Media Dordrecht 2014

Abstract The geochemical characteristics of geo-

phagic clays from Calabar and Okon-Eket, southern

Nigeria were evaluated to determine their quality and

the possible health effects of their consumption. The

study involved the measurement of the pH, electrical

conductivity (EC) and total dissolved solids (TDS) of

the slurried clay samples soaked in distilled water for

48 h using digital multi-parameters probe as well as

the elemental and mineralogical analyses of twenty

geophagic clay samples for elemental and mineralog-

ical constituents using both the ICP-MS and XRD,

respectively. Medical data were also mined from

medical facilities within the area in addition to the

administering of questionnaire to adults involved in

the geophagic practices in order to determine their

justification for the practice as well as their and clay

preferences. Results of physicochemical measurement

revealed that the pH range of the samples ranges from

3.9 to 6.9 and 6.5 to 7.0; EC 0.3–377.7 and

0.12–82.38 lS/cm; TDS 1.98–2,432.65 and

0.08–52.95 mg/L for consumed and non-consumed

clay, respectively. The elemental analyses revealed

that the concentration of some potential harmful

elements, PHEs, exceeded the recommended dietary

intake by humans. This is especially true for Cu

(9.1–23 ppm), Pb (16.7–55.6 ppm), Zn (13–148 ppm),

Ni (11.1–46.4 ppm), Co (1.8–21.7 ppm), Mn

(16–338 ppm), As (BDL-15 ppm) and Cd (BDL-

0.2 ppm). The predominant phases established in the

clay samples are quartz and kaolinite, while the minor

minerals were montmorillonite and muscovite in all

the clay samples. Respondents revealed that capacity

for relief from gastrointestinal problems believes in

the curative power to cure skin infections and cultural

reasons as main justification for the geophagic prac-

tices. This is, however, not in conformity with

information gleaned from the medical records which

still indicated that the prevalent diseases in the area

still include gastrointestinal problems in addition to

malaria, hypertension and cardiac failure with minor

cases of respiratory tract infections. The high concen-

trations of the PHEs may be responsible for or

contribute in part to the prevalence of hypertension,

cardiac failures and gastrointestinal problems within

the study areas. Though the kaolinite present in the

geophagic clays makes them suitable for use as

traditional antacids; however, the toxic trace element

concentrations and significant quartz content will most

likely mask the beneficial effects of such kaolinite.

Keywords Geophagic � Kaolinite �Montmorillonite � PHEs � Geochemical

evaluation

A. S. Olatunji (&) � J. O. Olajide-Kayode �A. F. Abimbola

Department of Geology, University of Ibadan, Ibadan,

Nigeria

e-mail: [email protected];

[email protected]

123

Environ Geochem Health

DOI 10.1007/s10653-014-9619-2

Author's personal copy

Introduction

Geophagy is the deliberate consumption of soil,

especially those of clayey composition. It is a specific

type of pica, which is the craving and subsequent

consumption of non-food substances (Young et al.

2008; Johns and Duquette 1991). This deliberate

consumption of earthy (geologic) materials, such as

soils, clays and chalk common amongst primates, is a

complex human behaviour which has for long been a

source of fascination and puzzle and according to Bisi-

Johnson et al. (2010), may be considered as a deviant

eating disorder.

Historically and in many traditional subsistence

societies, geophagy is almost synonymous with clay

consumption and is a normal human activity (Laufer

1930). The practice of geophagia has been reported to be

in existence as early as the fourth century and is practised

in several countries across continents including Africa

(South Africa, Cameroon, Nigeria, Swaziland, Demo-

cratic Republic of Congo, Tanzania and Uganda), Asia

(China, India, Guatemala, New Guinea, The Philippines

and Thailand), Australia, Europe and the Americas

(Reilly and Henry 2000; Woywodt and Kiss 2002;

Zeigler 1997; Abrahams and Parsons 1997; Aufreiter

et al. 1997; Callahan 2003; Hunter and de Klein 1984;

Hunter 1973; Halsted 1968; Reid 1992; Vermeer 1966).

In Nigeria, cultural, cosmetic, nutritional and

medicinal justifications have been proposed for the

practice of geophagy. The geophagic practice is

prevalent in the south-eastern and southern parts of

the country, especially amongst pregnant women. It is

believed that when consumed, the clay makes the skin

of both the mother and the foetus smooth and beautiful.

Some women in Nigeria (and indeed in other parts of

Africa) believe that consumption of clays makes them

beautiful, whether they are pregnant or not.

Most geophagic individuals also eat the clays when

they have gastrointestinal problems such as diarrhoea

and ‘stomach heat’. Women also make pastes from the

geophagic clays which they rub on their skin and

sometimes that of their children. They believe the clay

slurry makes good skin-smoothening remedies.

Geophagic clays may be good sources of essential

nutrients like iron, calcium, sodium and potassium, but

they also contain heavy metals such as copper, zinc,

cadmium, arsenic and lead. This study is therefore

aimed at ascertaining the quality of geophagic clays in

southern Nigeria by evaluating their elemental and

mineralogical constituents. This is in addition to the

determination of physicochemical properties and to

establish possible links between the consumption of

the geophagic clays and the health of the geophagic

individuals.

Study location and geology

The study was carried out in Calabar and Okon-Eket,

both in southern Nigeria (Fig. 1). Geologically, the study

locations fall within the Nigerian sedimentary terrain and

are underlain by formations of the Calabar Flank and

Niger-Delta complex (Fig. 2). These sedimentary basins

are predominantly made up of alternating shale and

sandstone sequence. Limestone layers have also been

described in part of the Calabar flank (Fig. 3).

Materials and methods

Twenty clay samples made up of eleven processed and

nine raw samples were collected for the study. Thirteen

of the samples were identified as being consumed, while

the other seven were not usually consumed (Table 1).

The clays samples were air-dried, pulverised with

20 g of each sample soaked in 120 mL distilled water

for 48 h in order to allow for the measurements of the

physicochemical parameters using the Hach eco 40

multi-pH metre. Subsequently, 0.5 g portion of the

pulverised samples was digested by a four-acid

combination and analysed for elemental composition

using inductively coupled plasma mass spectrometry.

The mineral composition of the samples was deter-

mined using the X-ray diffraction technique.

Questionnaires were also administered to geopha-

gic adults within the study areas to determine their

clay preferences, history and justification of practice

as well as consumption rate. This was in addition to

medical records that were also obtained from medical

facilities within the study areas in order to ascertain

prevalent diseases in the area.

Results and discussion

Physicochemical properties

The pH values of the consumed samples range

from 6.5 to 7.0, while the non-consumed samples


123


have pH values varying from 3.9 to 6.9; electrical

conductivities (EC) of the consumed samples range

from 0.3 to 377.71 lS/cm, those of the non-

consumed samples range from 0.12 to 82.38 lS/

cm. The total dissolved solids (TDS) in the

consumed samples range from 1.98 to 242.65 mg/

L, while the non-consumed samples had a range of

0.08–52.95 mg/L (Table 1). The physicochemical

parameters revealed that the consumed clay sam-

ples whether raw or processed have pH values that

are just slightly acidic to neutral compared to some

of the non-consumed samples that have very low

pH values.

Nutritional characteristics

The results of the elemental composition of the

consumed geophagic clays reveal that the concentra-

tion of essential micronutrients such as Ca, P, Mg, Na

and K are low, while appreciable concentrations of Fe

(0.49–5.95 %) and Al (7.58–14.46 %) were observed

(Table 2).

A comparison of the elemental oxide content of the

geophagic clays reveals that the processed clays have

higher values for CaO, MgO and K2O, while the

values for the Al2O3 are similar. A comparison of

clays from Calabar to Okon-Eket revealed that

Fig. 1 Map of study area

indicating sampling

locations


123


Okon-Eket clays have a wider range of concentrations

for FeO, Fe2O3, CaO, MgO, TiO2, Al2O3, Na2O and

K2O. Clays from Calabar have a wider concentration

range for MnO than clays from Okon-Eket, and Okon-

Eket and Calabar clays have the same concentration

range for P2O5 (Table 2).

Trace element content

The results of the concentration of selected heavy

metals (Table 3) in the analysed geophagic clays are

Cu (9.1–23.0 ppm), Pb (16.7–55.6 ppm), Zn (13.0–

148.0 ppm), Ni (11.1–46.4 ppm), Co (1.8–21.7 ppm),

Mn (16.0–338.0 ppm), As (BDL-15.0 ppm) and Cd

(BDL-0.2 ppm).

The presence of Pb, As and Cd in the samples is

itself a problem as these metals have no prescribed

guidelines for their consumptions owing to their

extreme toxic nature. All the other metals also

exceeded the recommended daily intake of trace

elements in the human body (Belitz et al. 2009) and the

minimum risk level prescribed by the Agency for

Toxic Substances and Disease Registry (ASTSDR

2012) (Table 3).

Minimal risk level (MRL) is the estimate of daily

human exposure to a hazardous substance at or below

which that substance is unlikely to pose a measurable

risk of harmful (adverse), non-cancerous effects.

A comparison of average concentration of the

trace elements revealed that Cu, Zn, Ni, and As

concentrations are higher in the consumed samples

across the study locations, while the non-consumed

clays contain higher concentrations of Pb and Co.

Cd concentrations were similar in both sample

types (Fig. 4).

The consumed samples from Calabar have higher

concentration of Cu, Pb, Zn, Ni and Co, while

consumed clays of Okon-Eket have higher average

concentration of As.

The raw and processed consumed clays from

Calabar have higher Pb content, while the processed

clays have higher Cu, Zn, Ni, Co, As and Cd (Fig. 4).

Fig. 2 Location and

generalised geology of the

Calabar Flank and Niger-

Delta Basin


123


However, for samples from Okon-Eket, raw samples

have higher concentrations of Cu, Ni, Co and As,

while concentrations of Pb and Zn are higher in the

processed samples with the average Cd concentrations

in raw and processed clays of Okon-Eket being the

same (Fig. 4).

Mineralogical composition

X-Ray diffraction analysis of six of the consumed

geophagic clays (OECR2, CCCP3, CCCP4, CCCP5,

CCCR1 and OECCP2) revealed kaolinite

(23.6–60.0 %), as the major clay mineral, while minor

montmorillonite (6.2 %) was also detected. The major

non-clay minerals identified are quartz (14.4–75.7 %)

and muscovite (3.3 %) (Table 4). Typical diffracto-

grams are shown in Fig. 5.

The probable origin of the geophagic clay minerals

is probably secondary minerals re-precipitated by

weathering of primary minerals (k-feldspar and micas)

in the shale interbeds within the sandstone of the Awi

and Benin formations as represented in Eqs. (1) and

(2).

2KAl3Si3O10 OHð Þ2K�feldspar

þ2Hþ þ 3H2O

! 3Al2Si2O5 OHð Þ4Kaolinite

þ2Kþ ð1Þ

2KAlSi3O8Mica

þ2Hþ þ 9H2O

! Al2Si2O5 OHð Þ4Kaolinite

þ2Kþ þ 4H4SiO4 ð2Þ

However, considering the high silica/quartz content

in the samples, another possible formation mechanism

for kaolinite could have been from the alteration of

feldspathic sandstones rich in quartz (Ekosse et al.

2010).

Prevalent health problems

Medical records from community health centres in the

study areas revealed that malaria is the most prevalent

ailment (37.4 %); this is not unexpected at the areas

that are within tropical environment. It is, however,

revealing that there is a significant record for the

occurrence of hypertension (20.6 %), gastrointestinal

problems (12.6 %) and cardiac failure (18.8 %). There

were also reported occurrences of respiratory tract

Fig. 3 Stratigraphic section of a typical mine site for geophagic clays


123


infections (RTI), dysentery, helminthiasis, plasmodi-

asis, anaemia and pneumonia (Fig. 6).

Potential health effects of the consumption

of the geophagic clays

The consumed geophagic samples analysed have pH

values ranging from 6.5 to 7.0, indicating that they are

generally slightly acidic to neutral. The pH of saliva is

alkaline; hence, a chemical reaction is expected to

occur between the clays and saliva in the mouth. The

slightly acidic nature of the clays are neutralised by the

alkalinity of the saliva, thereby probably responsible

for the feeling of tastelessness experienced by the

geophagic individuals when they consume the clays.

The slightly acidic nature of the consumed samples

may also generate an astringent effect in the mouth; an

effect useful in controlling the excessive secretion of

saliva and could be beneficial during pregnancy to

reduce nausea (Ngole et al. 2010).

The concentrations of heavy metals that are of

health and environmental concern in the samples in

quantities exceeding the recommended daily intake

of trace elements in the human body (Belitz et al.

2009), and the minimum risk level prescribed by

the Agency for Toxic Substances and Disease

Registry (ASTSDR 2012) is a cause for concern

(Tables 4, 5).

The relatively high prevalence of diseases such as

hypertension, cardiac failure, gastrointestinal prob-

lems as well as RTI may be due to the consumption of

these metal laden geophagic clays.

Specifically, hypertension which has a prevalence

of 20.6 % could result from exposure to lead and

sodium; cardiac failure which has an 18.8 % preva-

lence rate could be a resultant effect of ingestion of

toxic elements such as cobalt, arsenic, nickel, phos-

phorus and even potassium. Cadmium, copper, arsenic

and zinc can cause gastrointestinal problems, while

respiratory tract infections can be induced by toxic

levels of cobalt, arsenic, nickel, manganese, zinc,

magnesium and iron. It was also observed that there is

only very minimal improvement in the lowering of the

concentration of the potentially toxic metals in the

processed geophagic clays when compared to the raw

samples (Table 5).

The significant amounts of quartz in the clays also

pose risk to the health of the consumers as quartz is

harder that dental enamel (which is composed essen-

tially of apatite) and can therefore have a damaging

effect during mastication of the geophagic clays. Also,

the quartz within the ingested clay pass through the

gastrointestinal tract unaltered and may be lodged in

the colon. These unaltered particles, due to their

abrasiveness, may lacerate or even rupture the colon

leading to perforation (Jahanshahee et al. 2004).

On the other hand, however, the presence of

kaolinite in the geophagic clays agrees with the

protection hypothesis prescribed by Young et al.

(2008), given that kaolin minerals have long been used

in pharmaceutical formulations (e.g. Kaopectate,

Kapectolin, Kao-Spen, K–C suspension, Mist Kaolin

and other antacids) to treat the causes and symptoms of

gastrointestinal distress (Gonzalez et al. 2004). To this

end, the geophagic clays would provide relief from

gastrointestinal disorder to the consumer, acting as a

traditional antacid.

According to responses from the geophagic indi-

viduals in the administered questionnaires, the prac-

tice is prevalent amongst the very active population

(Fig. 7). This is a very disturbing observation as there

is a very strong possibility of having the various side

Table 1 Physicochemical properties of the clays analysed

Sample ID pH EC

(ls/cm)

TDS

(mg/L)

Remark

CCCR1 6.7 3.66 2.34 Raw, consumed

CCCP1 6.8 17.78 11.37 Processed, consumed


CCCP3 6.8 7 4.9 Processed, consumed


CCCP5 6.6 6 3.84 Processed, consumed

OECR1 7.0 0.3 34.28 Raw, consumed

OECR2 7.0 44.54 28.65 Raw, consumed

OECCP1 7.0 12.58 8.05 Processed, consumed





CNCCR1 6.7 0.5 0.32 Raw, not-consumed





OENCR1 6.8 0.12 0.08 Raw, not-consumed

OENCR2 6.7 82.38 52.95 Raw, not-consumed


123


effects highlighted above being prevalent amongst the

same set of population. This certainly has a serious

implication for the socio-economic well-being of

these communities.

Conclusion

Diverse reasons were adduced by geophagic individ-

uals in the study areas for the practice which include

Table 2 Major oxide composition of the geophagic clays

Oxide CNCCR1 CNCCR2 CNCCR3 CNCCR4 CNCCR5 CCCR1 CCCP1 CCCP2 CCCP3 CCCP4

SiO2(calculated) 73.95 71.22 78.89 73.85 70.84 71.38 78.23 70.03 69.23 74.93

Al2O3 22.4 24.61 18.59 22.55 22.5 23.57 18.32 24.12 15.58 20.25

FeO ? Fe2O3 1.5 2.9 1.39 1.53 4.68 2.82 1.27 3.56 11.97 2.43

Na2O 0.03 0.03 0.02 0.03 0.03 0.03 0.08 0.04 0.05 0.83

K2O 0.52 0.4 0.3 0.53 0.63 0.63 0.63 0.75 0.76 0.24

CaO 0.01 0.03 0.01 0.03 0.03 0.01 0.03 0.01 0.52 0.03

MgO 0.12 0.08 0.07 0.12 0.2 0.2 0.12 0.27 1.97 0.08

MnO 0.007 0.005 0.005 0.006 0.007 0.006 0.002 0.006 0.037 0.003

TiO2 1.58 0.99 0.83 1.48 1.52 1.6 1.4 1.54 1.1 1.4

P2O5 0.05 0.05 0.03 0.05 0.08 0.07 0.07 0.06 0.09 0.08

Oxide CCCP5 OECR1 OECR2 OENCR1 OECCP1 OECCP2 OECCP3 OENCR2 OECCP4 OECCP5

SiO2(calculated) 69.41 65.9 77.47 65.77 66.08 73.98 74.6 77.48 70.02 70.93

Al2O3 24.16 18.89 15.23 16.34 27.31 21.04 20.1 18.21 24.99 14.32

FeO ? Fe2O3 4.24 14.12 6.31 15.39 4.58 3.52 2.77 2.53 2.66 11.28

Na2O 0.04 0.07 0.05 0.14 0.03 0.18 1.08 0.34 0.04 0.07

K2O 0.74 0.86 0.41 1.87 0.58 0.2 0.23 0.24 0.63 0.71

CaO 0.01 0.03 0.03 0.04 0.03 0.01 0.03 0.04 0.03 0.62

MgO 0.27 0.35 0.25 0.35 0.22 0.08 0.08 0.08 0.18 2.07

MnO 0.006 0.021 0.014 0.303 0.007 0.003 0.003 0.004 0.005 0.044

TiO2 1.54 1.27 0.9 1.46 1.61 1.27 1.36 1.27 1.67 1.14

P2O5 0.07 0.06 0.04 0.04 0.07 0.09 0.07 0.08 0.06 0.07

Table 3 Comparison of average concentration of trace elements in geophagic clays with recommended daily intakes

Element Calabar Okon-Eket Recommended daily intake

(mg/day)bATSDR MRL (ppm/

day)c

Range

(ppm)

Average

(ppm)

Range

(ppm)

Average

(ppm)

ASC

(ppm)a

Cu 7.6–19.3 14.13 5.7–23.0 12.17 50 1.0–1.5 0.01

Pb 16.7–55.6 36.48 19.4–47.5 33.80 20 No safe threshold No safe threshold

Zn 13.0–148.0 46.00 15.0–114.0 41.29 90 10–15 0.3

Ni 11.1–46.4 23.87 11.2–36.3 22.60 80 0.025–0.03 0.0002

Co 1.8–21.7 6.78 1.8–16.7 5.77 20 0.002–0.1 0.01

Mn 16.0–284.0 76.83 22.0–338.0 106.43 850 2–5 –

As BDL-6.0 3.33 2.0–15.0 6.00 10 – 0.005

Cd BDL-0.2 0.05 BDL-0.2 0.10 0.3 – 0.0005

a Average Shale Content; Turekian and Wedepohl (1961)b Belitz et al. (2009)c ATSDR Minimum Risk Levels (2012)


123


relief from gastrointestinal problems, topical applica-

tion to cure skin infections, satisfaction of cravings,

leisure and cultural reasons. These geophagic clays are

usually obtained from valleys and riverbeds and

mildly treated by heat to make the clays more

palatable for consumption through sundrying, baking,

burning and sometimes a combination of any. Most of

the respondents consume the clays without any

processing, while some respondents scrape and make

into slurry before consumption. This practice has been

in existence for as long as the communities can

remember.

This work had revealed that geophagic clays from

Calabar and Okon-Eket are slightly acidic to neutral in

nature. Analysis of the elemental composition

revealed that Fe and Al are the nutrients derivable

from consumption of the geophagic clays which are

highly siliceous with considerable amounts of Cu, Pb,

Zn, Ni, Co, Mn, As and Cd in concentrations that

exceed the levels recommended for intake by humans.

Kaolinite is the major clay mineral, while mont-

morillonite is the minor. Quartz is present in minor to

significant quantities, and muscovite is present in very

minor amount. The presence of minor to significant

amount of kaolinite makes the clays usable as

traditional antacids. However, the concentration of

toxic elements and significant quartz content of the

geophagic clays make them unsuitable for consump-

tion and could outweigh the antacid effect that the

clays could have on the consumers. Consumption of

the clays will therefore have more negative effects

than positive.

Fig. 4 Average concentrations of selected metals in clay samples from southern Nigeria

Table 4 Quantitative mineralogical data for selected geophagic clays

Sample Quartz Kaolinite Montmorillonite Muscovite

wt% Abundance wt% Abundance wt% Abundance wt% Abundance

OECR2 75.7 Moderate-significant 24.3 Minor – – – –

CCCP3 14.4 Minor 23.6 Minor-moderate 6.2 Moderate – –

CCCP4 61.7 Moderate-significant 38.3 Minor-moderate – – – –

CCCP5 40 Moderate 60 Moderate-significant – – – –

CCCR1 34.8 Moderate 58.1 Moderate – – 3.3 Very minor

OECCP2 53.7 Moderate-significant 46.3 Moderate – – – –


123


Geophagy is an age-long practice that has persisted

and is common amongst rural and suburban dwellers

in the study areas and in the light of findings in this

work where a significant occurrences of ailments that

may have resulted from the consumption of these clays

have been reported and archived in clinics and

hospitals in the localities, it is recommended that

efforts should be put in place to sensitise the populace

Fig. 5 Typical diffractograms of processed and raw geophagic clays from southern Nigeria

Fig. 6 Prevalent health problems in the study area

Table 5 Comparison of selected metals in raw and processed

consumed clay samples from the study area

Metals Calabar (Median

values in ppm)

Okon-Eket

(Median values in

ppm)

aATSDR

MRL

(ppm/day)

Raw Processed Raw Processed

Cd BDL 0.15 0.15 0.1 0.0005

Zn 22.0 36.0 41.0 26.0 0.3

As 6.0 4.5 10.5 4.0 0.005

Cu 6.3 17.3 10.2 10.7 0.01

Ni 17.7 24.8 20.9 22.0 0.0002

Co 2.4 4.5 6.2 3.3 0.001

Pb 35.3 29.8 31.2 31.0 No safe

threshold

a ATSDR minimum risk levels 2012


123


on the inherent dangers in the continuation of this

practice without the necessary safeguards.

References

Abrahams, P. W., & Parsons, J. A. (1997). Geophagy in the

tropics: An appraisal of three geophagical materials.

Environmental Geochemistry and Health, 19(1), 19–22.

Agency for Toxic Substances and Disease Registry (ATSDR)

(2012). Minimal risk levels.

Aufreiter, S., Hancock, R. G. V., Mahaney, W. C., Stambolic, R.

A., & Sanmugadas, K. (1997). Geochemistry and miner-

alogy of soils eaten by humans. International Journal of

Food Sciences and Nutrition, 48(5), 293–305.

Belitz, H. D., Grosch, W., & Schieberle, P. (2009). Food

chemistry. p 425.

Bisi-Johnson, M. A., Obi, C. L., & Ekosse, G. E. (2010).

Microbiological and health related perspectives of geo-

phagia: An overview. African Journal of Biotechnology,

9(19), 5784–5791.

Callahan, G. N. (2003). Eating dirt. Emerging Infectious Dis-

eases, 9(8), 1016–1021.

Ekosse, G. E., de Jager, L., & Ngole, V. (2010). Traditional

mining and mineralogy of geophagic clays from Limpopo

and Free State provinces, South Africa. African Journal of

Biotechnology, 9(47), 8058–8067.

Gonzalez, R., Demedina, F. S., Martinez-Augustin, O., Nieto,

A., Galvez, J., Risco, S., et al. (2004). Anti-inflammatory

effect of diosmectite in hapten-induced colitis in the rat.

British Journal of Pharmacology, 141, 951–960.

Halsted, J. A. (1968). Geophagia in man: Its nature, and nutri-

tional effects. American Journal of Clinical Nutrition, 21,

1384–1393.

Hunter, J. M. (1973). Geophagy in Africa and the United States:

Culture-nutrition hypothesis. Geographical Review, 63,

170–195.

Hunter, J. M., & de Kleine, R. (1984). Geophagy in Central

America. Geographical Review, 74, 157–169.

Jahanshahee, A., Pipelzadeh, M. H., & Ahmadinejad, M. (2004).

A case report of colon and rectum obstruction because of

sand in a three-year-old boy. Archives of Iranian Medicine,

7(1), 66–67.

Johns, T., & Duquette, M. (1991). Detoxification and mineral

supplementation as functions of geophagy. American

Journal of Clinical Nutrition, 53, 448–456.

Laufer, B. (1930). Geophagy. Field Museum of Natural History

Anthropology Series, 18, 99–198.

Ngole, V. M., Ekosse, G. E., de Jager, L., & Songca, S. P.

(2010). Physicochemical characteristics of clayey soils

from South Africa and Swaziland. African Journal of

Biotechnology, 9(36), 5929–5937.

Reid, R. M. (1992). Cultural and medical perspectives on geo-

phagia. Medical Anthropology, 13, 337–351.

Reilly, C., & Henry, J. (2000). Geophagia: Why do humans

consume soil? Nutrition Bulletin, 25(2), 141–144.

Turekian, K. K., & Wedepohl, L. H. (1961). Distribution of

elements in some major units of the Earth crust. American

Geological Society Bulletin, 72, 125.

Vermeer, D. E. (1966). Geophagy among the Tiv of Nigeria.

Annals of the Association of American Geographers, 56(2),

197–204.

Woywodt, A., & Kiss, A. (2002). Geophagia: The history of

earth-eating. Journal of the Royal Society of Medicine, 95,

143–146.

Young, S. L., Wilson, M. L., Miller, D., & Hillier, S. (2008).

Towards a comprehensive approach to the collection and

analysis of pica substances with emphasis on geophagic

materials. PLoS ONE, 3(9), e3147.

Zeigler, J. L. (1997). Geophagy: A vestige of paleonutrition?

Tropical Medicine & International Health, 2(7), 609–611.

Fig. 7 Age of respondents across the study locations


123


Evaluation of geochemical characteristics of some geophagic clays, southern Nigeria

Documents

Transcript of Evaluation of geochemical characteristics of some geophagic clays, southern Nigeria