Characterization and Safety of Clays as Potential Dietary Supplements to Prevent Aflatoxicosis

Aflatoxins are toxic metabolites produced by Aspergillus flavus and A. parasiticus fungi. Aflatoxin B1 (AFB1) is the most toxic and is a potent carcinogen with antinutritional and immunosuppressive effects. Several natural outbreaks of poisoning have been reported in both animals and humans, with fatal consequences in some of the cases. Inclusion of clay minerals in the diet is a promising strategy to reduce the bioavailability of aflatoxins from contaminated foods. Several clay-based products are currently sold as ?mycotoxin binders? for addition in feeds, many of them lacking of detailed efficacy and safety data. Similarly, clays intended for human consumption in different countries also lack of safety studies, and for most of them the mineral composition is unknown. Earlier studies in our laboratory have shown that NovaSil clay (NS), a Ca-bentonite, is able to reduce the adverse effects associated with aflatoxin exposure in different animal species and recent human trials have confirmed its efficacy and safety. Most clays are derived from naturally-occurring deposits and batch-to-batch variations in composition, particle size, non-framework trace metal content and dioxin levels are expected. Therefore, objectives in this research were to determine the mineral composition, aflatoxin binding capacity and potential safety of ?mycotoxin binders? and edible clays for humans, and to investigate the mineral characteristics and safety of two potential aflatoxin adsorbents, a refined clay with more uniform particle size (UPSN) and a sodium bentonite (Na-BENT). Both clays have low dioxin/furans and heavy metals levels. According to mineralogical analysis, most of the ?binders? contained montmorillonite but the sorption capacities for AF varied. Most of the edible clays for humans contained kaolinite, mica and quartz, and they had low sorption capacities for aflatoxin. UPSN and Na-BENT had similar mineral characteristics and high sorption capacities for aflatoxin. After a 3-month rodent study using Sprague Dawley rats, no overall toxicity was observed for either clay. No changes were observed for most of the blood and serum biochemical parameters. Important findings included the increased serum Na, Ca, vitamin E and Na/K ratio and the reduction of serum K and Zn (in males) due to ingestion of the bentonites. Nonetheless, all parameters fell within the normal ranges reported for rats less than 6 months old and no trends of dose dependency were observed. We conclude that ingestion of low levels of bentonites does not present a health risk.