Geoscience Reference
In-Depth Information
SOURCE OF ESSENTIAL NUTRIENTS
All living organisms require certain naturally occurring elements (essential nutrients)
for their metabolism to function efficiently. For humans there are 14 elements that are
believed to be essential. These are: calcium, chromium, copper, fluorine, iodine, iron,
magnesium, manganese, molybdenum, phosphorus, potassium, selenium, sodium, and
zinc (Price, 2000). The ultimate source of these elements is the natural environment.
From the dawn of time human beings have obtained the essential nutrients by eating
plants that accumulated these elements from the soil; by eating meat from animals that
accumulated the elements from plants or from animals that had obtained the elements
from plant eating organisms lower in the food chain; by drinking water in which the
nutrients are suspended or dissolved; or by directly ingesting soil (Geophagea). Today
many people rely on vitamin pills to augment their daily requirements of the essential
elements but the elements in vitamin pills are ultimately derived from rocks, minerals,
or natural waters.
Geophagy or geophagea is a Greek word meaning “eating earth”. It refers to the
practice of people in almost every society to eat soil as part of their diet (Figure 2).
Pica is a similar term that is commonly applied to the tendency of children to inten-
tionally eat unnatural substances such as soil. The craving to eat soil, principally clay,
may be physiological in nature or may have derived from observation of animals that
eat soil, clay, pebbles, and so on. Soil may constitute 10% or more of what grazing
animals ingest (Abrahams, 2005). Certain birds are known to ingest clays prior to eat-
ing toxic fruits. The clays apparently act to detoxify the fruits. In Africa, wild yams, an
important source of nutrients during time of famine, can be eaten if detoxifi ed through
ingestion of clay (Abrahams, 2005). American Indians have also been known to mix
soil with acorns, tubers, and berries to render them edible.
Figure 2.
(a) Eating clay; (b) Loesss (wind-blown sand) pills produced in Germany.
