National Geographic is reporting on an interesting story about self medicating by eating dirt. Chimps in Uganda’s Kibale National Park have been observed eating dirt. Not just any dirt, though, but a type rich in kaolinite:
Experts had previously suggested that chimps ate the fine-grained clay to help ward off intestinal ailments or to obtain added minerals in their diet.
Recent research published in Naturwissenschaften suggests a different reason. Chimps also eat Trichilia rubescens. What happens when the two are combined is quite interesting.
From National Geographic:
Eating the bitter vegetation alone gives the chimps no health benefit, researchers say. Instead the plant’s malaria medicine is activated when fine soil particles bind with chemicals in the leaves.
Like humans, chimps can suffer the potentially fatal effects of malaria, although the types of Plasmodium parasites that cause the disease in chimps are different from the four known to infect people.
In previous laboratory studies, Krief’s team had found that extracts of the Trichilia plant were effective in fighting the parasite that causes malaria in chimps.
“I noticed that the chimps often eat soil just before or after eating Trichilia leaves,” Krief said. “I wondered what might be the effect of mixing the two substances.”
The researchers tested the idea by grinding up the leaves of Trichilia rubescens and soaking them in a solution that mimiced the digestive juices in the chimp stomach. Then they looked for antimalarial activity. None was observed. They repeated the procedure, this time adding samples of the soil consumed by the chimps. This time the results were positive. In theory the relationship looks good. The one caveat is that this has not been tested in living chimps.