The Folic Acid and Creatine Trial: Treatment Effects of Supplementation on Arsenic Methylation Indices and Metabolite Concentrations in Blood in a Bangladeshi Population

Abstract

Background: Chronic arsenic (As) exposure is a global environmental health issue. Inorganic As (InAs) undergoes methylation to monomethyl (MMAs) and dimethyl-arsenical species (DMAs); full methylation to DMAs facilitates urinary excretion and is associated with reduced risk for As-related health outcomes. Nutritional factors, including folate and creatine, influence one-carbon metabolism, the biochemical pathway that provides methyl groups for As methylation.

Objective: Our aim was to investigate the effects of supplementation with folic acid (FA), creatine, or the two combined on the concentrations of As metabolites and the primary methylation index (PMI: MMAs/InAs) and secondary methylation index (SMI: DMAs/MMAs) in blood in Bangladeshi adults having a wide range of folate status.

Methods: In a randomized, double-blinded, placebo (PBO)-controlled trial, 622 participants were recruited independent of folate status and assigned to one of five treatment arms: a) PBO ($n=102$), b) $400\mu g$ FA/d (400FA; $n=153$), c) $800\mu g$ FA/d (800FA; $n=151$), d) $3g$ creatine/d (creatine; $n=101$), or e) $3g\text{creatine}+400\mu g\text{of FA}/d$ ($\text{creatine}+400\text{FA}$; $n=103$) for 12 wk. For the following 12 wk, half of the FA participants were randomly switched to the PBO while the other half continued FA supplementation. All participants received As-removal water filters at baseline. Blood As (bAs) metabolites were measured at weeks 0, 1, 12, and 24.

Results: At baseline, 80.3% ($n=489$) of participants were folate sufficient ($\ge 9\text{nmol}/L$ in plasma). In all groups, bAs metabolite concentrations decreased, likely due to filter use; for example, in the PBO group, blood concentrations of MMAs (bMMAs) ($\text{geometric mean}\pm \text{geometric standard deviation}$) decreased from $3.55\pm 1.89\mu g/L$ at baseline to $2.73\pm 1.74$ at week 1. After 1 wk, the mean within-person increase in SMI for the $\text{creatine}+400\text{FA}$ group was greater than that of the PBO group ($p=0.05$). The mean percentage decrease in bMMAs between baseline and week 12 was greater for all treatment groups compared with the PBO group [400FA: $-10.4$ (95% CI: $-11.9$, $-8.75$), 800FA: $-9.54$ (95% CI: $-11.1$, $-7.97$), creatine: $-5.85$ (95% CI: $-8.59$, $-3.03$), $\text{creatine}+400\text{FA}$: $-8.44$ (95% CI: $-9.95$, $-6.90$), PBO: $-2.02$ (95% CI: $-4.03$, 0.04)], and the percentage increase in blood DMAs (bDMAs) concentrations for the FA-treated groups significantly exceeded that of PBO [400FA: 12.8 (95% CI: 10.5, 15.2), 800FA: 11.3 (95% CI: 8.95, 13.8), $\text{creatine}+400\text{FA}$: 7.45 (95% CI: 5.23, 9.71), PBO: $-0.15$ (95% CI: $-2.85$, 2.63)]. The mean decrease in PMI and increase in SMI in all FA groups significantly exceeded PBO ($p<0.05$). Data from week 24 showed evidence of a reversal of treatment effects on As metabolites from week 12 in those who switched from 800FA to PBO, with significant decreases in SMI [$-9.0\%$ (95% CI: $-3.5$, $-14.8$)] and bDMAs [$-5.9\%$ (95% CI: $-1.8$, $-10.2$)], whereas PMI and bMMAs concentrations continued to decline [$-7.16\%$ (95% CI: $-0.48$, $-14.3$) and $-3.1\%$ (95% CI: $-0.1$, $-6.2$), respectively] for those who remained on 800FA supplementation.

Conclusions: FA supplementation lowered bMMAs and increased bDMAs in a sample of primarily folate-replete adults, whereas creatine supplementation lowered bMMAs. Evidence of the reversal of treatment effects on As metabolites following FA cessation suggests short-term benefits of supplementation and underscores the importance of long-term interventions, such as FA fortification. https://doi.org/10.1289/EHP11270.

Trial registration: ClinicalTrials.gov NCT01050556.