The Role of Dietary and Environmental Metals in Cardiometabolic Health

Metals are natural components of the earth’s crust, although they can also be introduced to the environment through human activities. While some metals are required in trace amounts for human health, others are known toxicants. With this work, we evaluated the associations of metal exposures with cardiometabolic conditions using secondary data from three distinct study populations. Our first analysis estimated dietary and supplemental intakes of copper, manganese, selenium, and zinc, which are considered nutritionally essential, within a cohort of Hispanic and Latino adults living within the United States. We then assessed cross-sectional and prospective associations of these intakes with metabolic syndrome, a clustering of cardiometabolic conditions. For most metals, greater intakes appeared to be protective against existing and new cases of metabolic syndrome over a 6-year period, but greater selenium intakes were associated with an increased risk of developing dyslipidemia. In our second analysis, we examined co-exposures to the same four essential metals in addition to four toxic metals (arsenic, cadmium, lead, and mercury) with metabolic syndrome using data from the cross-sectional National Health and Nutrition Examination Survey, 2011-2014. In this general United States adult population, metal concentrations were measured in samples of blood, serum, or urine. We again observed selenium in addition to selenium-zinc co-exposures to be positively associated with dyslipidemia. Novel findings from this analysis included an inverse association of cadmium-lead co-exposures with abdominal obesity and positive associations of arsenic-mercury co-exposures with low HDL cholesterol, and high triglycerides. Lastly, we analyzed blood concentrations of lead, manganese, and selenium within a longitudinal study of adults in Bangladesh. Blood lead concentrations in this population were very high, and those most exposed experienced increases in systolic blood pressure annually during the 6-year follow-up period. However, manganese concentrations within a narrow range between 8.2 and 10.0 μg/L and selenium concentrations above 136 μg/L were associated with decreases in blood pressure over time, suggesting these essential metals may have potential as antihypertensives. Overall, our results indicate the metal exposures are important risk or protective factors for cardiometabolic health, but associations likely depend upon the dose of exposure and possibly on the geographic context.