Evaluation Of Food-Chain Mycotoxin Exposure In Rural Zimbabwe: Determinants, Effects And Mechanisms

Abstract

Mycotoxins are toxins produced by mold that are commonly present in staple foods such as maize and groundnuts that are widely consumed by billions of people and are a direct threat to global food safety and food security. Aflatoxin and two other mycotoxins, fumonisin and deoxynivalenol, are of particular concern to human health because they are highly prevalent in the food chain and may have substantial negative health consequences. The overall aim of this dissertation is to evaluate the determinants, effects and biological mechanisms of food chain mycotoxin exposure in the context of rural Zimbabwe. First, I conduct two literature reviews to evaluate existing human, animal and cellular evidence for the causal relationship between mycotoxins, particularly aflatoxin, and child stunting and adverse birth outcomes. Second, I describe aflatoxin exposure in a cohort of women during early pregnancy in rural Zimbabwe over one calendar year, and explore potential determinants of exposure, particularly seasonality, agroecology, and dietary practices using multiple ordinal regression. Third, informed by causal aims one and two, I evaluate the potential relationship between biomarker of aflatoxin exposure (AFM1) and biomarkers of intestinal (fecal myeloperoxidase and [alpha]1-antitrypsin) and systematic immune activation (serum C-reactive protein and [alpha]1-antitrypsin) in rural Zimbabwean pregnant women using fractional polynomial analysis. We developed two frameworks proposing inflammation as a potential causal mechanism by which aflatoxin may interfere with fetal development and child growth. We found that one third of pregnant rural Zimbabwean women had detectable aflatoxin M1 in their urine indicating recent exposure to aflatoxin (range= 37-6000 pg/mg creatinine) with significant temporal and spatial variation in exposure. We have also found that recent exposure to aflatoxin is associated with markers of intestinal and systemic inflammation, and this association is non-linear. This research has implications for nutrition and food security programming because it indicates that aflatoxin exposure is a threat to global food safety and health as it is common and associated with inflammation which is a biologically plausible mechanism by which aflatoxin could cause adverse birth outcomes and child stunting.