A composition and method for use as a preventive therapy to mitigate the effects of environmental toxins, and particularly aflatoxins in a subject. The subject may be at risk for hepatocellular carcinoma and aflatoxicosis. The composition comprising: an effective amount of an isolated low sodium, calcium aluminosilicate clay in a powder form, wherein the isolated low sodium, calcium aluminosilicate clay contains acceptable levels of dioxins and priority toxic heavy metal contamination, and is capable of preferentially binding aflatoxins in the gastrointestinal tract.