Calabash chalk is a clay substance that is popularly consumed in West African countries for pleasure, religious beliefs, and as a cure for nausea in pregnant women.
The practice of deliberating consuming earth, soil, or clay is called geophagia and is very popular in African countries. Though, the chalk can also be found in ethnic stores in the UK, US, Canada, and among African women in the US state of Georgia.
In different countries, calabash chalk is known by different names such as Calabar stone (English), la craie or argile (French), nzu or ulo (Igbo in Nigeria), mabele (Lingala in Congo), ndom (Efik/Ibibio in Nigeria), poto, shilè (Ghana) and umcako (Zulu in South Africa).
The chalk is available in powder or molded spheres and is made from mining pits, anthills, or by mixing clay, wood ash, salt, and sand. Majorly, it is composed of kaolin but also contains lead, arsenic, and chromium.
Over the years, many people, particularly pregnant women, have grown a liking to it because of the belief that it can help treat heartburn, diarrhea, morning sickness, and skin diseases.
Despite its vast usefulness, the side effects of consuming calabash chalk remain still largely unknown.
Read on to discover some side effects that are linked to the consumption of calabash chalk.
10 Possible Side Effects of Eating Calabash Chalk (Nzu)
1. Empty nutrition
Calabash chalk contains zero nutrition. It will not give you any of the essential nutrients your body needs. It is deficient in carbohydrates, dietary fiber, protein, fats, or vitamins.
Clearly, it deprives you of healthy nutrition and fills your system with toxic elements instead.
2. Calabash chalk is addictive
Believe it or not, it is easy to get addicted to calabash chalk, just like you can with nicotine or drugs. The salty and earthy smell that reminds you of the first downpour of rain on dry soil drives you to consume more and more (even if you try to fight it).
Don’t let the cravings draw you back in – cut off the potential for addiction.
3. Ingestion of toxic chemicals
Calabar chalk is predominantly composed of aluminum silicate hydroxide, a type of kaolin. It also contains 10-50 mg/kg of lead – an amount that exceeds the 1 mg/kg recommended value of lead in food.
In addition, it has rich amounts of arsenic, chromium, aluminum, silicon, alpha lindane, endosulfan 11, and other organic pollutants – chemicals that are known to cause poisoning and tissue damage in the body .
4. Risk of infertility
According to a 2018 study, scientists found that regular or prolonged consumption of calabash chalk in animal models may alter growth rate and cause changes to the uterus – which could be damaging to the reproductive system.
The experts advised women of reproductive age to desist from consuming calabash chalk. 
5. Toxicity in pregnancy
Research, carried out on the effect of consuming calabash chalk in pregnancy, found negative effects due to its high content of lead and arsenic.
One study in pregnant rats who were fed calabash chalk found that dose-dependent consumption of calabash chalk caused loss of pregnancy, stillbirth, and inhibited maternal weight gain and fetal growth .
However, human studies are required to determine the exact doses and mechanism of action.
6. May cause developmental issues in children
Exposing toxic minerals such as lead to infants and growing children can cause slowed growth and developmental issues – as lead easily crosses the placenta to the fetus during pregnancy.
One study tested the blood of the umbilical cord of pregnant women who consumed calabash chalk and found high levels of lead – suggesting that lead could have been easily transferred from mother to infant during pregnancy .
7. May affect bone health
Pregnant women who consume calabash chalk may unknowingly pass lead to their infants during pregnancy, and an accumulation can cause delayed bone growth.
One animal study found that ingestion of nzu caused demineralization of the femur bone and altered growth rate in rats .
8. Increased risk of digestive issues
Due to the high composition of toxic chemicals, regular consumption of calabash chalk can cause constipation, stomach upset, nausea, and vomiting.
Researchers found edema and bleeding in the stomach of animal models fed with 40 mg/ml of calabash chalk for 14, 21, and 28 days respectively .
9. Increased risk of anemia
Regular and prolonged consumption of calabash chalk can cause anemia, especially in women of childbearing age.
One study found that this chalk changed the concentration of hemoglobin, red blood cell count, platelet count, and erythrocyte sedimentation rate in rats .
10. Risk of parasitic infestations
Most calabash chalk producers only think of monetary gain and will go to any length to make profits – including mining the chalk from soil surfaces contaminated with feces and organic matter.
Chalk derived from this method may contain the eggs of parasitic organisms like tapeworm and other nematodes, leading to infestation.
Is Calabash Chalk (Nzu) good for Pregnant Women?
In pregnancy, many women crave non-food items like clay and ice. This condition is called Pica – a Latin name for magpie (Pica pica), a bird that eats almost anything.
It occurs when iron and zinc are deficient, which may arise if nausea and vomiting limit the amount of nutrients you’re taking in.
Non-food items like nzu have no nutritional value and may expose you and your infant to toxins. So it is best to avoid it in pregnancy.
Can Calabash Chalk help me to lose weight?
Calabash chalk coats the lining of the stomach, preventing the normal absorption of nutrients from food. This can give you a false perception of weight loss whereas you are missing out on essential nutrients.
In the long run, the risks outweigh the benefits.
The bottom line
Calabash chalk is an interesting geophagic material that is consumed for pleasure, nausea, vomiting, and religious beliefs.
Unfortunately, it contains toxic chemicals, parasites, and microorganisms that pose a great health risk in pregnant women and normal people.
So, it’s best to avoid regular and prolonged consumption.
I hope you found this article helpful, leave your questions below, and don’t forget to share!
- Dean, J. R. et al. (2004). Characterization and analysis of persistent organic pollutants and major, minor, and trace elements in Calabash chalk. Chemosphere.
- Opara, Julia & Nwagbaraocha, Eileen. (2018). The effect of calabash chalk on the uterus of adult female Wistar rats. GSC Biological and Pharmaceutical Sciences.
- Aprioku, J. S., & Ogwo-Ude, E. M. (2018). Gestational Toxicity of Calabash Chalk (Nzu) in Wistar Rats. International journal of applied & basic medical research.
- Brice Nguedia Vofo et al. High umbilical cord blood lead levels and “Calabar chalk” consumption amongst pregnant women in two hospitals in Cameroon. Pan African Medical Journal.
- Ekong, M. B. et al (2012). Evaluation of calabash chalk effect on femur bone morphometry and mineralization in young Wistar rats: A pilot study. International journal of applied & basic medical research.
- Moses, B. et al. (2012). Effect of calabash chalk on the histomorphology of the gastro-oesophageal tract of growing Wistar rats. The Malaysian journal of medical sciences
- Akpantah, A. O. et al. (2010). The effect of calabash chalk on some hematological parameters in female adult Wistar rats. (Calabash chalk) Turkish journal of hematology: official journal of Turkish Society of Hematology
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