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 lg FA/d (400FA; n = 153), c) 800 lg FA/d (800FA; n = 151), d) 3 g creatine/d (creatine; n = 101), or e) 3 g creatine + 400 lg of FA/d (creatine + 400FA; n = 103) for 12 wk. For the following 12 wk, half of the FA participants were ran-domly 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 (≥9 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) (geometric mean ± geometric standard deviation) decreased from 3:55 ± 1:89 lg/L at baseline to 2:73 ± 1:74 at week 1. After 1 wk, the mean within-person increase in SMI for the creatine + 400FA 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), creatine + 400FA: −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), creatine + 400FA: 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 supple-mentation 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.