Consumption of folate-related nutrients and metabolism of arsenic in Bangladesh

Background: Inorganic arsenic (InAs) is metabolized to monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), and this methylation facilitates urinary arsenic excretion. Previous studies suggest that persons with more complete methylation, characterized as greater proportions of DMA and lesser proportions of MMA and InAs in urine, have a lower risk of adverse arsenic-related health outcomes. Objective: The purpose of this study was to examine whether the capacity to methylate arsenic differs by nutrient intake. Design: Participants were 1016 Bangladeshi adults exposed to arsenic in drinking water. Nutrient intake was assessed with a validated food-frequency questionnaire. Multivariate regression analyses were used to examine associations of nutrients with urinary arsenic metabolite profiles. Results: In multivariate analyses, higher intakes of cysteine, methionine, calcium, protein, and vitamin B-12 were associated with lower percentages of InAs and higher ratios of MMA to InAs in urine. Higher intakes of niacin (β = 0.22, P = 0.02) and choline (β = 0.10, P = 0.02) were associated with higher DMA-to-MMA ratios, after adjustment for age, sex, smoking, total urinary arsenic, and total energy intake. Conclusions: Findings from the current study show the influence of multiple nutrients on arsenic methylation. In particular, this study highlights the potential importance of dietary intakes of cysteine, methionine, niacin, vitamin B-12, and choline on health effects of arsenic by modulating its metabolism.