Role of Diet in Heavy Metal Exposure and Toxicity during Prenatal and Peripubertal Periods

Abstract

Nutrition is a valuable consideration in environmental risk assessment, given the interaction of nutrients with toxicants at source, body burden, and health effect. Heavy metal toxicants – cadmium and lead – can be introduced through foods with absorption impacted by nutrients and nutritional status and once internalized, exert toxic effects such as oxidative stress depending on competing nutritional antioxidants. This dissertation assesses nutrient and toxicant interactions during sensitive time periods – prenatal and peripubertal – in the ELEMENT birth cohorts from Mexico City. Unique exposures are likely given individual and population-wide changes in dietary habits and have profound long-term health effects during development periods. Cardiometabolic health during adolescence – the focus of this dissertation – is relevant given that Mexico has an increasing prevalence of childhood obesity, a risk factor for cardiovascular disease, diabetes, hypertension, and dyslipidemia.

The first aim assesses cadmium exposure using both estimated dietary intake and a urinary biomarker. Diet was a significant source of cadmium exposure among pregnant women and children unexposed to cigarette smoke, with vegetables – mainly leafy greens – contributing. The second aim explores the relationship between cadmium exposure and adiposity during adolescence. Prenatal cadmium exposure was negatively associated with measures of both abdominal and peripheral adiposity in girls, but not in boys, and remained an independent predictor of adiposity after additionally adjusting for concurrent cadmium exposure and confounding by maternal lead exposure and dietary intake. The third aim describes the creation of an antioxidant diet score in mothers and adolescents, and examines whether this antioxidant score is directly associated with adolescent cardiometabolic outcomes and modifies associations between lead exposure and these outcomes. Maternal antioxidant intake positively associated with adiposity where adolescent intake was inversely associated with fasting blood glucose. At both time points, antioxidant diet score simultaneous to lead exposure attenuated the cardiometabolic effects of lead, but given weak relationships with the oxidative stress marker, mechanisms may not be entirely related to the antioxidant potential of the diet. These studies provide evidence for the dynamic role of diet in heavy metal exposure and toxicity where mechanisms may depend on timing of exposure.