Eat dirt? Why on earth would you do that

Eating soil is a common practice in Africa. With very little research into the practice of geophagy, however, best estimates put the percentage somewhere between 30 per cent and 80 per cent of the population.

Because it is most commonly associated with pregnant women, it was assumed to be a craving related to some nutritional deficiency – iron, zinc, and so on – found in clayey soil, that some in the developing world might not be able to afford to purchase in supplement form.

However, as the number of people in Africa – both male and female – routinely eating soil has grown, researchers at the MedUni Vienna’s Centre for Public Health, Institute of Social Medicine, decided to take a closer look at geophagy.

A paper published in The American Journal of Tropical Medicine and Hygiene, describes soil eating as potentially habit forming. "Pregnant and breast-feeding women, in particular, nearly always have some soil to eat as it is cheap to buy in the marketplace," says Ruth Kutalek of MedUni Vienna's Centre for Public Health (Institute of Social Medicine) and lead author of the study.

Describing soil-eating as a craving, the authors compared it to chocolate’s impact on the human neurological reward system. “People often eat clay as a snack between meals and report that they could not do without it,” she said.

Soil contains clay, known for its binding properties, especially to unwanted toxins, and so could work as a medicine of sorts (similar to the way charcoal tablets help combat diarrhoea).

Clay may also positively influence the pH of stomach acid and help relieve heartburn – an issue for many African women living on a diet of maize, cassava and pulses. The Viennese research group also found evidence for soil as a soothing antidote to morning sickness.

Cultural factors

Various African ethnic groups consider soil-eating to be a “womanly” activity, usually indicating she may be pregnant. According to the MedUni experts, however, a growing number of men have begun eating soil too. In some parts of Africa, clay is regarded as a natural stimulant for men.

As the numbers rise, surveys conducted by the researchers found many people admitting to craving soil when they didn’t have any, leading to the assumption that some addictive element must also be at play.

"There's already evidence to show how geophagy is common among those with iron and/or zinc deficiencies but we are yet to fully investigate whether other minerals present in the soil might also be needed by humans," says Prof Mike Gibney, Emeritus Professor in Food and Health at UCD. "We know there are chemicals essential for human life only found in soil such as cobalt, chromium and molybdenum.

Prof Gibney cites existing research into the motivation behind geophagy. “Clinical trials have been carried out in areas prone to geophagy elsewhere,” he says. “Locals were given mineral supplements and a placebo, with equal impacts. So it can’t be motivated entirely by some mineral deficiency. There must be an addictive element to it.”

Public health

Eating soil may provide some nutritional value. But overall, it is not advised. Soil can contain metals such as lead or mercury, especially in Africa. Consuming large quantities of these kinds of metals would be particularly harmful to men and women, not to mention unborn babies. “It is therefore strongly recommended that consumption be reduced,” says Kutalek, co-author of the study.

Habit forming or not, the elephant in the room is that this practice (which at various points in history was also common in Europe and Asia) is found mostly in Africa. Economic necessity plays a role in the dietary choices people make worldwide. Therefore, if soil, which is cheap and widely available, is believed to provide badly needed minerals such as zinc or iron, then telling people to stop eating it without providing an affordable alternative isn’t going to change behaviour.

“Human beings are fussy eaters,” says Gibney. “When we have foods in plentiful supply, disgust enters the fray. “I, for example, wouldn’t eat locusts. But if I was dying of starvation, I’d eat however many I could get my hands on. There is a point where dignity and disgust go out the window. However, there’s more to it in this case as the practice of eating soil in Africa has cultural dimensions to it. Certain soils are considered to have medicinal benefits and are often mixed with herbs as remedies for various ailments.”

As stated, one of the principle reasons cited for consuming soil is for its perceived high iron content. However, a study conducted in 2000 suggests this already bitter pill to swallow might not even benefit in this regard. According to a paper entitled, The Impact of Consuming Iron from Non Food Sources on Iron Status in Developing Countries, increasing one's absorption of iron through soil comes with the "simultaneous absorption of contaminant iron that has joined the common pool. Any positive effect of geophagy resulting from an increased intake of iron, therefore, is highly unlikely due to inhibiting constituents contained in soils and clays."

Further research

Further research into geophagy continues at MedUni Vienna’s Centre for Public Health. Meanwhile, soil has been found on sale around Europe, usually on supermarkets aisles in localities which cater for large migrant African populations. Some health food stores in Europe offer bentonite clay for internal use too. Officially, it is not advisable to consume clay of any kind.