Folic acid supplementation lowers blood arsenic

Am J Clin Nutr. 2007 Oct;86(4):1202-9. doi: 10.1093/ajcn/86.4.1202.


Background: Chronic arsenic exposure currently affects >100 million persons worldwide. Methylation of ingested inorganic arsenic (InAs) to monomethylarsonic (MMAs) and dimethylarsinic (DMAs) acids relies on folate-dependent one-carbon metabolism and facilitates urinary arsenic elimination.

Objective: We hypothesized that folic acid supplementation to arsenic-exposed Bangladeshi adults would increase arsenic methylation and thereby lower total blood arsenic.

Design: In this randomized, double-blind, placebo-controlled trial, we evaluated blood concentrations of total arsenic, InAs, MMAs, and DMAs in 130 participants with low plasma folate (<9 nmol/L) before and after 12 wk of supplementation with folic acid (400 microg/d) or placebo.

Results: MMAs in blood was reduced by a mean +/- SE of 22.24 +/- 2.86% in the folic acid supplementation group and by 1.24 +/- 3.59% in the placebe group (P < 0.0001). There was no change in DMAs in blood; DMAs is rapidly excreted in urine as evidenced by an increase in urinary DMAs (P = 0.0099). Total blood arsenic was reduced by 13.62% in the folic acid supplementation group and by 2.49% in the placebo group (P = 0.0199).

Conclusions: Folic acid supplementation to participants with low plasma concentrations of folate lowered blood arsenic concentrations, primarily by decreasing blood MMAs and increasing urinary DMAs. Therapeutic strategies to facilitate arsenic methylation, particularly in populations with folate deficiency or hyperhomocysteinemia or both, may lower blood arsenic concentrations and thereby contribute to the prevention of arsenic-induced illnesses.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Arsenic / blood
  • Arsenic / metabolism*
  • Arsenic / urine
  • Arsenicals / metabolism
  • Arsenicals / urine
  • Bangladesh / epidemiology
  • Dietary Supplements*
  • Double-Blind Method
  • Environmental Exposure / adverse effects
  • Female
  • Folic Acid / administration & dosage
  • Folic Acid / blood
  • Folic Acid / pharmacology*
  • Homocysteine / blood
  • Humans
  • Male
  • Methylation / drug effects*
  • Middle Aged
  • Vitamin B Complex / administration & dosage
  • Vitamin B Complex / blood
  • Vitamin B Complex / pharmacology*
  • Water Pollutants, Chemical / blood
  • Water Pollutants, Chemical / metabolism*
  • Water Pollutants, Chemical / urine


  • Arsenicals
  • Water Pollutants, Chemical
  • Homocysteine
  • Vitamin B Complex
  • Folic Acid
  • monomethylarsonic acid
  • Arsenic