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I. Overview

As
eating disorders have begun to become more widely recognized by the public and medical
field, there are still several eating disorders that have yet to be as
publicized—Pica. Pica is defined as an eating disorder characterized by a
craving for the ingestion of unusual and non-nutritious substances (Lacey,
1990). The DSM-5 outlines the criteria in diagnosing an individual with Pica.
The criterion includes the ingestion of nonfood substances for at least 1
month, ingested substances are “inappropriate to the developmental level of the
individual,” and eating behavior is not due to the cultural norms (“Pica”,
2017). It is also suggested that the individual is at least 2 years of age
before being diagnosed (“Pica”, 2017).

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The
prevalence of Pica is difficult to assess because of its underreporting and its
stigma (“Pica”, 2017). There are many forms that exist—pagophagia (ice eating),
stachtophagia (cigarette ash eating), etc. (Moore & Sears, 1994). For the
purpose of exploring the adaptive value of Pica through a Tinbergen lens, this
essay will focus on one subset, geophagia: the consumption of the earth, soil,
and/or clay (Moore & Sears, 1994).

 

II. Development and
Mechanism

Studies
into the mechanism underlying geophagia and its incidence through development
suggest that there may be a connection between mechanism and development. Although
the underlying mechanism of this eating disorder is not fully understood, one
hypothesis is mineral deficiencies cause an individual to develop geophagia
(Rose et al., 2000). This idea stems from observations where geophagic patients
are frequently iron deficient, and when this iron deficiency is treated, the
eating disorder subsides (Rose et al., 2000). Iron is crucial in hemoglobin synthesis,
and its deficiency is dangerous because it may lead to anemia, a severe stage
of iron deficiency (Yadav & Chandra, 2011). Low iron levels result in an insufficient
amount of oxygen in tissues and negative effects upon cellular and bodily
functions (Yadav & Chandra, 2011). These negative consequences result in
downstream effects of “abnormal growth and behavior” (Yadav & Chandra,
2011). Precisely, iron deficiency may have adverse effects on cognitive
function and brain development (Yadav & Chandra, 2011).

 

Although
Pica may occur at any age, statistics indicate that infants, children, and
pregnant women commonly fall victims (“Pica,” 2017; Woywodt & Kiss, 2002). Infants
are at a greater risk of iron deficiency compared to other developmental stages
(Moy & Early, 1999). This increased risk may be due to an early
introduction of cow’s milk, a poor iron source (Moy & Early, 1999). It is
important that infants after the age of 4 months obtain iron through
supplements or diet (Moy & Early, 1999). Unfortunately, parents often fail
to do so (Moy & Early, 1999). It has been distinguished that infant iron
deficiency tends to coincide with when the brain undergoes a growth spurt
(Yadav & Chandra, 2011). These iron deficient children are later seen to
“have lower IQ scores, decreased attentiveness,” and decreased academic
excellence compared to non-iron deficient children (Yadav & Chandra, 2011).
Furthermore, Pica is found to be quite prevalent within children with
intellectual disabilities and autism (“Pica,” 2017). This suggests that there
may be some mechanistic link where iron deficiency causing alterations in the
brain lead to the development of Pica.

 

III. Mechanism

During
the late fetal and early neonatal period, the hippocampus, a region of the
brain that is crucial in “learning, memory, and cognition,” is sensitive to low
iron levels (Radlowski & Rodney, 2013). Low iron levels change the gene expression
that is vital in the proper development and function of the hippocampus
(Radlowski & Rodney, 2013). It may potentially be that the decreased iron
levels causing abnormal cognitive development of the brain also alter the same brain
region controlling for normal eating behaviors. An iron

deficient
diet may result in unusual brain development that also results in geophagy
onset.

 

IV. Phylogeny

Geophagic-eating
patterns are prominent across the animal kingdom. Geophagia is most commonly
reported in the bighorn sheep and other ungulates (Mincher et al., 2008). These
ungulates participate in “salt licking” to fulfill a sodium deficit (Mincher et
al., 2008). There is a case of Snowshoe Hares licking soils in iron rich areas
(Roy et al., 2013). The hares participate in geophagy mostly during the winter
and spring but hardly in the summer and autumn (Roy et al., 2013). Knowing that
nutritional stress is common in the winter and spring, it can be hypothesized
that these hares display geophagy when there is a nutrient deficiency; this
supports an adaptive value behind geophagy (Roy et al., 2013). Furthermore, conservation
of geophagy throughout the animal kingdom is indicative that there must be an
adaptive value behind it or evolution would not have evolved this trait.

 

V. Adaptive Value

Geophagia
is maladaptive because consistent ingestion of foreign substances may be toxic
to the body, and there has been speculation that continual ingestion may lead
to even lower iron levels since clay and soil inhibit iron absorption (Lacey,
1990). However, embedded in the vulnerability to geophagia is the adaptive
value to fulfill nutritional deficiencies in the short term and decrease the
chances of anemia. Studies upon iron and calcium levels of geophagic materials propose
a nutritional value behind them (Engberg, 1995). Analysis of the ingested items
has shown to provide 15% of the recommended iron and calcium daily allowances
to pregnant women (Engberg, 1995). Furthermore, a similar study upon locally
produced clay in Latin America indicates that the clay delivers 9% of the
recommended daily allowance for iron and other minerals (Engberg, 1995). Knowing
that anemia can lead to health complications such as fatigue, enlarged heart or
heart failure, and potentially death, it would be adaptive to consume items
that would offset a potential anemia onset (“Anemia,” 2017). Ingesting earth
materials continuously is maladaptive; when an individual notices these
abnormal eating behaviors, he/she must respond by fulfilling those nutritional
needs through other options. In the short term, geophagy would serve to temporarily
fulfill nutritional deficits while also signaling these deficits to the
patient. Geophagy would be especially adaptive in a changing environment where
nutritional foods are not seasonally abundant.

 

VI. Experiment

One
may test this adaptive hypothesis by utilizing rats and splitting them into two
groups. Both groups would be induced to be iron deficient, and the experimental
group would be fed geophagic substances. By evaluating the iron levels after
two weeks, if the hypothesis were to be true, the geophagic rats would have
improved iron levels compared to the control.

 

VII. Summary

Being
informed of the geophagy’s adaptive value and looking at it comparatively helps
to destigmatize this disorder. Geophagy may be maladaptive, but to a limited
extent, it can be adaptive in preventing the anemia onset especially within
changing environments where nutritious foods vary.

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