Providing a Scientific Basis for the Use of a Healing Clay Among the Uitoto of the Colombian Amazon

Indigenous peoples have accrued valuable environmental knowledge, including geology and its impacts on health. The Uitoto people of the Colombian Amazon observed that certain clay collected from nearby creeks aliviated fever, gastrointestinal ailments, and nausea. Using modern analytical methods and ethnogeology techniques, the mode of action of the clay they used (AMZ clay) was investigated. This study adds to existing knowledge about healing clays, which humans have used for thousands of years even without understanding the details of their efficacy.

This work combined methods from ethnography, microbiology and geochemistry. The traditional knowledge of healing clays was studied through interviews with cultural experts and participative field trips. Clay samples were collected and Escherichia coli was used as model bacteria in order to study both the chemical exchanges and the distribution of elements after treatments with the hydrated clay overnight. The role of clay absorption of bacterial nutrients was investigated. Membrane permeabilization was tested using Vancomycin, a large antibiotic molecule that cannot cross a healthy bacterial membrane.

Results showed that the AMZ clay is dominated by weathered kaolin minerals. Cation exchange of the clay removed 108 ppm Al, and trace transition metals implicated in the antibacterial process. The clay adsorbed P from the culture medium, but even when excess P was added back, bacteria was not able to resume growth. This indicated that nutrient depletion was not the cause of death. Rather, the Vancomycin experiment indicated an increased membrane permeability after AMZ exposure. Furthermore, nano-scale secondary ion mass spectrometry (NanoSIMS) documented that Al was significantly higher in the bacterial cell membrane, possibly binding to membrane phospholipids. The Fe concentration increased significantly inside the bacteria exposed to AMZ, compared to untreated controls. These observations are consistent with other clays shown to kill bacteria by metal toxicity. This study exemplifies how the scientific understanding of an ancient practice of the Uitoto people might be used to promote the use of clays in healthcare.