Mineral and chemical analyses of soils eaten by humans in Indonesia

Five Javanese soil samples, including three earths eaten by humans as thera peutic medicine, were analyzed for their physical, mineral and chemical pro perties along with suitable control samples (not eaten). The eaten soils ha ve a high content of hydrated halloysite and kaolinite, that is, clay miner als that are pseudoforms of the pharmaceutical Kaopectate(TM). Along with h ydrated halloysite in a ratio of nearly 1:1, the expandable clay mineral sm ectite is also present, but in much greater quantity than is usually found in Kaopectate(TM). Among the chemical elements that may act as a stimulus f or geophagy, only Na, Mn, K and S are possible candidates driving this beha vior. Sodium is inherent in the minerals derived from the volcanic bedrock; and it is present in a form other than NaCl. Iron, which is often higher i n soils eaten by both human and nonhuman primates, and has therefore been r egarded in the past as a possible stimulus for geophagy, is relatively high in these soils, but does not have a higher concentration in the eaten soil s relative to the uneaten soils in this group of samples. Cobalt and chromi um, two important trace elements in human nutrition and diet, are marginall y but not markedly higher in the eaten samples. The eaten soils in all case s have predominantly higher levels of 1:1 clay minerals than the 2:1 minera ls which may predominate in some of the control soils, which some studies h ave associated with health problems. Soils can adsorb dietary toxins, prese nt in the plant diet or those produced by microorganisms. Taking the toxic alkaloids quinine, atropine, sparteine, and lupanine as examples, it is evi dent that soils from Ampo (southern Java) have a very good adsorptive capac ity, comparable to that of coal or charcoal. Other Javanese soils also adso rb these toxins, but to a lesser degree.