Geophagy

related topics
{disease, patient, cell}
{food, make, wine}
{woman, child, man}
{theory, work, human}
{acid, form, water}
{specie, animal, plant}
{black, white, people}
{company, market, business}
{island, water, area}
{god, call, give}

Geophagy is the practice of eating earthy or soil-like substances such as clay, and chalk, in order to obtain essential nutrients such as sulfur and phosphorus from the soil. This practice is widespread among animals in the wild, as well as in human societies. Human geophagy is closely related to pica, a classified eating disorder in the DSM-IV characterized by abnormal cravings for nonfood items.[1]

Geophagy is most often seen in rural or preindustrial societies among children and pregnant women.[2]

Contents

Animal geophagy

Geophagy is extremely widespread in the animal kingdom. Galen, the famous Greek philosopher and physician, was the first to record the use of clay by sick or injured animals back in the second century AD. This type of geophagy has been documented in "many species of mammals, birds, reptiles, butterflies and isopods, especially among herbivores."[3]

Geophagy is well documented in birds. Notably, many species of South American parrots have been observed at clay licks, whilst Sulphur-crested Cockatoos have been observed ingesting clays in Papua New Guinea (Discover, 1998) as well as in Glenbrook in Blue Mountains of Australia (Parrots Magazine, 2000). Analysis of most soils consumed by wild birds show that they prefer soils with high clay content, often with the smectite and bentonite clay families being well represented. In vitro and in vivo tests of these soils indicate that they release biologically important quantities of minerals like calcium and sodium, as well as adsorbing substantial quantities of small charged compounds such as alkaloids. Because the clays release minerals and adsorb other cations as part of the same process of cation exchange, it remains challenging to determine which function is the more important motivator in any given instance of avian geophagy. Separate from soil ingestion, pet birds are often provided with grit which is retained in their gizzards to aid in grinding the food they eat.

Full article ▸

related documents
Capsaicin
Laudanum
Pediatrics
Circulatory system
Vulvodynia
Obstetrics
White blood cell
Achondroplasia
Gastrointestinal tract
Cardiomyopathy
Barbiturate
Progesterone
Gynaecology
Breast reconstruction
Exocrine gland
Spasticity
Cerebral cortex
Pelizaeus-Merzbacher disease
Tylenol
Clitoris
Thalamus
Echinococcosis
Lambert-Eaton myasthenic syndrome
Tumor suppressor gene
Meconium aspiration syndrome
Goitre
Diuretic
Artificial respiration
Dendritic cell
Nerve