The practice of intentionally consuming soil is already known to cause a string of health problems.
For a long time, scientists suspected it also contributes to the high burden of throat cancer in Kenya, especially western Kenya.
But a new study in Kenya, Tanzania and Malawi shows there is no evidence to link the practise, called geophagia, to throat cancer.
“In conclusion, geophagia is too rare to contribute to the male esophageal squamous cell carcinoma burden in Africa. In women, the practice is common but we did not find consistent evidence of a link to ESCC,” they said in a study published last week in the International Journal of Cancer.
Moi University School of Public Heath took part in the study.
Throat cancer is common in the region from Ethiopia to South Africa, which is now know as African oesophageal cancer corridor.
For years, scientists have been searching for reasons behind the high burden.
The practice of stone eating is also common in this region and is well established to cause intestinal problems.
“We investigated whether this practice is linked to endemic esophageal squamous cell carcinoma in this region,” the researchers said.
Although pleasurable and somewhat a necessity among pregnant women, stone eating exposes women to potentially hazardous substances like bacteria, fungi, radioactive materials, and toxic elemental minerals in the soil depending on the geographical location.
The scientists found that it is rare among men in Kenya.
They said the study cannot rule out selection bias masking its modest effects.
“Physical effects of geophagia do not appear to have a large impact on overall ESCC risk. Research with improved constituent-based geophagia exposure assessment is needed.”
Kenya has an age-standardised throat cancer incidence of 8.3 per 100,000 people. This means at least 12,000 oesophageal cancer cases are diagnosed in Kenya every year.
It is commonest in the Rift Valley, especially in Keiyo, Uasin Gishu and Nandi.
Dr Shaheen Sayed, a pathologist at Aga Khan University Hospital, recently theorised the incidence could be linked to volcanic soils, tobacco chewing or smoking and the traditional fermented milk (mursik), which contains ash.
Scientists also point at heavy alcohol consumption and smoking, but other risk factors have been documented as well.
In 2019, Moi University researchers published a paper linking the cancer to the practice of drinking “very hot” beverages, even if the patients took no alcohol or tobacco.
“This trend was consistent in males, females, never and ever alcohol/tobacco and was stronger over than under age 50 years,” they said.
Recent work from Kenya also found increased throat cancer risk associated with poor oral health, including an ill-understood association with dental fluorosis.