title: Creatinine, diet, micronutrients, and arsenic methylation in West Bengal, India.
abstract: BACKGROUND
  Ingested inorganic arsenic (InAs) is methylated to monomethylated (MMA) and dimethylated metabolites (DMA). Methylation may have an important role in arsenic toxicity, because the monomethylated trivalent metabolite [MMA(III)] is highly toxic.
  
  
  OBJECTIVE
  We assessed the relationship of creatinine and nutrition--using dietary intake and blood concentrations of micronutrients--with arsenic metabolism, as reflected in the proportions of InAS, MMA, and DMA in urine, in the first study that incorporated both dietary and micronutrient data.
  
  
  METHODS
  We studied methylation patterns and nutritional factors in 405 persons who were selected from a cross-sectional survey of 7,638 people in an arsenic-exposed population in West Bengal, India. We assessed associations of urine creatinine and nutritional factors (19 dietary intake variables and 16 blood micronutrients) with arsenic metabolites in urine.
  
  
  RESULTS
  Urinary creatinine had the strongest relationship with overall arsenic methylation to DMA. Those with the highest urinary creatinine concentrations had 7.2% more arsenic as DMA compared with those with low creatinine (p < 0.001). Animal fat intake had the strongest relationship with MMA% (highest tertile animal fat intake had 2.3% more arsenic as MMA, p < 0.001). Low serum selenium and low folate were also associated with increased MMA%.
  
  
  CONCLUSIONS
  Urine creatinine concentration was the strongest biological marker of arsenic methylation efficiency, and therefore should not be used to adjust for urine concentration in arsenic studies. The new finding that animal fat intake has a positive relationship with MMA% warrants further assessment in other studies. Increased MMA% was also associated, to a lesser extent, with low serum selenium and folate.
authors.affiliation: Arsenic Health Effects Research Group, School of Public Health, University of California, Berkeley, California 94720, USA.
authors.forename: Arin
authors.initials: A
authors.lastname: Basu
authors.forename: Soma
authors.initials: S
authors.lastname: Mitra
authors.forename: Joyce
authors.initials: J
authors.lastname: Chung
authors.forename: D N
authors.initials: DN
authors.lastname: Guha Mazumder
authors.forename: Nilima
authors.initials: N
authors.lastname: Ghosh
authors.forename: David
authors.initials: D
authors.lastname: Kalman
authors.forename: Ondine S
authors.initials: OS
authors.lastname: von Ehrenstein
authors.forename: Craig
authors.initials: C
authors.lastname: Steinmaus
authors.forename: Jane
authors.initials: J
authors.lastname: Liaw
authors.forename: Allan H
authors.initials: AH
authors.lastname: Smith
mesh_terms: D000293:Adolescent; D000328:Adult; D001151:Arsenic / Q000378:metabolism / Q000633:toxicity / Q000652:urine*; D001152:Arsenicals / Q000378:metabolism / Q000652:urine*; D003404:Creatinine / Q000652:urine*; D003430:Cross-Sectional Studies; D004032:Diet; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D007194:India; D008297:Male; D008745:Methylation; D018977:Micronutrients / Q000097:blood* / Q000378:metabolism; D008875:Middle Aged; D014874:Water Pollutants, Chemical / Q000378:metabolism / Q000652:urine*; D055815:Young Adult
chemical_list: D001152:Arsenicals; D018977:Micronutrients; D014874:Water Pollutants, Chemical; D003404:Creatinine; D001151:Arsenic