It is an ancient custom for Africans to eat soil, which is the result of adapting to nature for thousands of years. According to their theory, land is a symbol of women, because land nurtures everything, and women also shoulder the heavy responsibility of bearing children, so women in reproductive period should especially eat soil. South Africans have done research and found that soil contains 65 elements needed by human body. In addition, clay contains negatively charged particles, which prevent toxins in gastric juice from entering the blood and excrete toxins through the kidneys and intestines. In some parts of Africa, people use clay to treat diseases such as dysentery and cholera. Scientists have also sampled and tested the soil eaten by pregnant women in Tanzania and Nigeria, and found that eating 500 mg of clay every day can meet 80% of the calcium needs of pregnant women, and the detoxification of soil can protect the fetus. In addition, clay is generally weakly alkaline, which can neutralize gastric acid, reduce pregnancy reaction and relieve vomiting. In Africa, it is the secret of many tribes and families to find soil and mix it with it. However, the locals still gave reporters some hints: for example, the soil with "copper grass" must be rich in copper; The soil at the root of cycad contains iron and magnesium; The loose red soil near the ant nest is rich in iron and zinc; To ingest iodine, the bane of "big neck disease", the black mud deposited in the swamp is perfect. Of course, eating dirt is not the best way to keep fit, and eating it is ineffective or even counterproductive. Now in Africa, people in cities eat less and less soil. It is relatively convenient to seek medical advice and medicine, and it is not easy to find a suitable soil source in the city. However, in the vast rural areas, the disappearance of this custom can not be realized in one day.