Human health implications from co-exposure to aflatoxins and fumonisins in maize-based foods in Latin America: Guatemala as a case study

Abstract

Co-occurrence of fumonisin B 1 (FB 1 ) and aflatoxin B 1 (AFB 1 ) in maize has been demonstrated in many surveys. Combined-exposure to FB 1 and AFB 1 was of concern to the Joint FAO/WHO Expert Committee on Food Additives because of the known genotoxicity of AFB 1 and the ability of FB 1 to induce regenerative proliferation in target tissues. Humans living where maize is a dietary staple are at high risk for exposure to both mycotoxins. Our work has focused on Guatemala, a country in Central America where maize is consumed in large amounts every day and where intake of FB 1 has been shown to be potentially quite high using biomarker-based studies. In 2012 a survey was conducted which analysed maize samples for FB 1 and AFB 1 from all 22 departments of Guatemala. The results show that the levels of AFB 1 exposure are also potentially quite high in Guatemala, and likely throughout Central America and Mexico. The implications of co-exposure for human health are numerous, but one area of particular concern is the potential of FB 1 to modulate AFB 1 hepatoxicity and/or hepatocarcinogenicity. Both the mechanism of action of FB 1 and its ability to promote liver carcinogenicity in rats and rainbow trout is consistent with this concern. In farm and laboratory animals FB 1 inhibits ceramide synthases, key enzymes in de novo ceramide biosynthesis. The inhibition of sphingolipid signalling pathways mediating programmed cell death and activation of pathways stimulating cell proliferation in livers of individuals exposed to AFB 1 could contribute to the tumorigenicity of AFB 1 . Studies investigating the health effects of either toxin should consider the potential for co-exposure to both toxins. Also, in countries where maize-based food are prepared by alkaline treatment of the maize kernels, the effect of traditional processing on AFB 1 levels and toxicity needs to be determined, especially for maize highly contaminated with AFB 1 .