Content area
Full Text
(ProQuest: ... denotes non-US-ASCII text omitted.)
For thousands of years, people have used clay to heal wounds, soothe indigestion and treat intestinal pathogens. Nowadays, Kaopectate® and Smecta® are common commercial products featuring, respectively, kaolinite and smectite, that assuage diarrhoea in monkeys and humans(1,2). By lining the walls of the intestinal tract, healing clays protect the injured intestinal tract from irritation by toxins. More precisely, the presence of clay in the gut increases mucus secretion by goblet cells and prevents mucolysis through increased protein cross-linking(3).
Clays are microcrystalline minerals and have specific properties such as a layer charge, a high specific surface area (reaching values of about 800 m2/g), a high ion exchange capacity and a high adsorption capacity(4). They may therefore possess a strong nutrient retention power. It has indeed been shown that l-leucine, l-aspartate and d-glucose bind with a high affinity to the clay mineral bentonite(5). In that case, one may ask whether nutrients can be still efficiently absorbed in 'clay-plastered' intestines. On the other hand, also based on their properties, clay minerals could also be an appropriate substratum for enzymes (and should therefore favour hydrolysis of macronutrients and consequently intestinal absorption). Indeed, diosmectite, a natural clay used in the treatment of several gastrointestinal diseases, shows a dose-dependent capacity to adsorb some enzymes in vitro(6). Furthermore, kaolinite feeding in rats has been shown to increase the activity of leucine amino-peptidase and of several dehydrogenases(7).
Kaolinite, one of the simplest clay with an ideal chemical formula of Al2O3.2SiO2.2H2O, is usually the main clay provided to humans suffering from diarrhoea(8-11). In systemic mineralogy, kaolinite belongs to the category of phyllosilicates, which are stratified layered minerals. Because of the strong attractions between the layers, most reactivity of kaolinite is controlled by the external adsorption surface area of the particles. Kaolinite easily adsorbs water(12,13) and is known to selectively bind some noxious compounds in the digestive tract and to avoid their absorption by enterocytes. Among these substances, diarrhoea-causing...