Dietary clay in the chemoprevention of aflatoxin-induced disease

Aflatoxins are harmful by-products of mold growth and, though invisible tothe naked eye, are potentially fatal. The aflatoxin problem is long-standing and inextricable. Concerns about the aflatoxins originate from thestrong implications of their involvement in disease and death in humans andanimals, yet scientists and clinicians are still seeking ways toeffectively deal with these dangerous and elusive chemicals. Safe,practical, and effective strategies for the detoxification ofaflatoxin-contaminated food and feed are highly desirable. A simple andeffective approach to the chemoprevention of aflatoxicosis has been todiminish or block exposure to aflatoxins via the inclusion of HSCAS clay inthe diet. HSCAS clay acts as an aflatoxin enterosorbent that tightly andselectively binds these poisons in the gastrointestinal tract of animals,decreasing their bioavailability and associated toxicities. Further studiesto delineate the molecular mechanisms of action have shown that thedicarbonyl system of aflatoxin is essential for tight binding by HSCAS. Inthese studies, adsorption data was fitted to multiple isotherm equationsincluding the Langmuir, multi- Langmuir, general Freundlich,Langmuir-Freundlich, Toth and various transforms. Information derivedincluded: the Gibbs standard free energy change of adsorption, enthalpy ofadsorption, capacity, affinity, and heterogeneity coefficient. Computermodeling was also utilized to provide additional structural information andinsight into the mechanism. Evidence suggests that aflatoxins may react atmultiple sites on HSCAS particles, especially the interlayer region, butalso at edges and basal surfaces. Since clay and zeolitic minerals comprisea broad family of functionally diverse chemicals, there may be significanthidden risks associated with their indiscriminate inclusion in the diet.All aflatoxin binding agents should be rigorously tested, paying particularattention to their effectiveness and safety in aflatoxin-sensitive animalsand their potential for interactions with critical nutrients.