The US FDA has released a statement based on finding from the Texas Department of State Health Services on December 23, 2009:
The Texas Department of State Health Services is warning consumers, especially pregnant or breastfeeding women, to avoid consuming a traditional product called “Nzu” because of the potential health risks from high levels of lead and arsenic.
Nzu, which is consumed as a traditional remedy for morning sickness, has been found by DSHS food inspectors at two African specialty stores – one in the Dallas area and one in Houston. It was also found at a distributor in Houston. The product generally resembles balls of clay or mud and also is called Calabash clay, Calabar stone, Mabele, Argile and La Craie.
Laboratory analysis by DSHS found high levels of lead and arsenic in this product.
Exposure to lead can result in a number of harmful effects, and a developing child is particularly at risk of effects on the brain and nervous system. Arsenic is a carcinogen, and excessive long-term exposure to it has been associated with a range of adverse health effects, including cancers of the urinary bladder, lung and skin.
The Nzu may be covered in a brown or white “dust” and is usually sold in small plastic bags with a handwritten label identifying it as “Nzu” or “Salted Nzu.”
Anyone who has been ingesting the product should contact their health care provider.
The source of the product in Texas is not yet known. Inspectors with DSHS are continuing to investigate.
Ingesting soil, particularly mineral-rich clay, is a practice called geophagy. Various kinds of earth have been a folk remedy common to many cultures, primarily for gastrointestinal complaints.
Terra Sigillata was a fatty clay harvested from the Greek isle of Lemnos and contained at least one component found in today’s Kaopectate diarrhea remedy. A special ceremony would be held to harvest the clay where it would be cut into planchets, embossed with an official seal, then dried and sold. Terra Sigillata stands in pharmacy history as the first trademarked medicine.
Geophagy is also why South Carolinians are sometimes called “sandlappers” and why this Nigerian remedy is often called “Calabash Clay” or “Calabash Chalk.” (Calabash is a coastal town right at the border between North and South Carolina. A style of spiced seafood, usually shrimp, is also known as Calabash.)
But as regards “nzu,” a warning similar to that in Texas came out in 2002 from the Northern Ireland Department of Health, Social Services, and Public Safety (PDF).
In trying to dig up some literature, I believe this may be the first time I have entered a search term in PubMed and come up with zero returns. A search for Calabash chalk comes up with a 2004 paper in Chemosphere for which I cannot obtain full text. The abstract is suggestive that samples were analyzed for several elements and environmental contaminants, with 40 mg/kg of lead being present as well as pesticides. I believe that I will have to consult my geology or Nigerian colleagues for more information on this as I anticipate there is far more literature available but perhaps in regional journals not abstracted by the US National Library of Medicine. I’m primarily curious as to where such samples might be taken from so as to have such high levels of Pb.
In the meantime, I’ll be interested to learn later what case(s) in Texas spurred the current FDA action but I hypothesize that it involved pre-natal, post-natal, or maternal neurological toxicity.