Have you seen children dig out and lick soil or a mud wall? Some pregnant women crave for the soil too. Ever wondered why does that happen? This behaviour of voluntarily consuming soil is called Geophagy. Did you know the father of medicine, Hippocrates (460-380 BC) made a reference to geophagy in pregnancy (Young, 2011) and Celsus (14-37 AD) links geophagy to anaemia (Woywodt and Kiss, 2002)? Let us see why!

What is geophagy?

Geophagy or ingestion of soil is a phenomenon that attracted the attention of many researchers recently. A large number of animals, including Parakeets and Macaws consume natural soils of various areas. Geophagy is widespread among animals such as elephants, ungulates, primates, carnivores, birds and sometimes even humans. While the benefits of soil consumption are yet to be proven among humans, the reason behind the consumption has proven a mystery even today.

Krishnamani and Mahaney (Division of Conservation Biology, Salim Ali Centre for Ornithology and Natural History) published a study that explored the possibility of the medicinal benefits of consuming soil in animals. Mahaney also studies the possibility of self-medication by geophagy in the Japanese Macaques, Mountain gorillas and Chimpanzees. Though the study detected the choice of soil composition, it couldn’t conclusively prove the medicinal benefits from soil consumption.

Gorillas in the Virunga Mountains of Rwanda are known to mine the yellow volcanic rock from the slopes of Visoke mountain and powder the soil before eating it. It is also seen that this happened when they are forced to change their diet to plants such as bamboo, lobelia which have more toxic compounds than the usual diet. This change usually results in their bodies starting to reject the toxins and cause diarrhoea, fluid loss and weakness (Study by American Zoologist Dian Fossey, 1983). By consuming the soil from the volcanic slopes, gorillas seek Halloysite, which is used to treat human gastric ailments. Kaolinite aids in reducing diarrhoea by absorbing fluids in the intestines! Who taught the gorillas this?

It is also observed that termite ridden mounds are the favourite for geophagy among wild chimpanzees who eat mouthfuls of termite mounds. Similar behaviour is seen in giraffes, elephants, monkeys and rhinos!

Dietary choice or detox method?

Another behaviour observed among the elephants is that their diet is primarily leaves which usually contain some plant defense toxins that try to make the food unpalatable to the elephants. This builds up their toxin level in their body and scientists are of the opinion that elephants may be resorting to geophagy to help detoxify these elements in their bodies.

In humans, the cause for geophagy remains mysterious and though it is being studied from many decades, it is still a puzzle to be explored. While in many cultures, consuming soil is a part of rituals – Javanese and Vietnamese make thin tiles of clay in a systematic process – Soil is selected, filtered, cleaned, baked and cooked to make thin wafers which are then consumed. Similar preparations are found across the world including Kenya, Ghana, Guatemala, US, India, Africa and Britain.

Is geophagy new?

Not at all, say the scientists. Several archaeological studies have shown that along with animal bones, plant remains, the presence of clay samples hint at the consumption of soil in the Paleolithic age! Studies conducted by Johns and Duquette in 1991 on the samples of habitats in the Palaeolithic sites of Kalambo Falls, Zambia, dating to 200,000 years ago, found that nuts from plants were detoxified using clay soils and possibly consumed.  Recent excavation of a site dating to 1650 BCE, at Poverty Point, Louisiana found clay balls possibly meant for consumption.

Several studies conducted to understand why pregnant women in rural areas consume soil or develop a craving are yet to show any positive answers. So, do we crave for soil consumption in search of iron, calcium, magnesium as Laufer’s (1930) research shows? Or is it a behaviour trait we are yet to outgrow from? However, soil consumption among woman and children is proven unhealthy as humans cannot easily digest soil and also due to the contaminants in the soil including disease-causing elements. 

It is fascinating that macaws were observed resorting to clay lick and therefore prevent the plant alkaloids from entering into their blood. Another interesting fact is that both Macaws and other animals, including the elephants, reduce or almost stop the intake of soil when they have abundant fruits – especially in the months of September and October. So when they reduce the plant intake and binge on fruits, they do not need to look for geophagy anymore!

The next time you crave to eat soil, may be we should try a fruit first!

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