title: Inhibition of iron absorption by calcium is modest in an iron-fortified, casein- and whey-based drink in Indian children and is easily compensated for by addition of ascorbic acid.
abstract: BACKGROUND
  Calcium inhibits and ascorbic acid (AA) enhances iron absorption from iron-fortified foods. Absorption efficiency depends on iron status, although the interaction is unclear.
  
  
  OBJECTIVE
  We investigated the ability of AA to overcome calcium-induced inhibition of iron absorption in children differing in iron status.
  
  
  METHODS
  The effect of calcium (0, 100, and 200 mg/test meal) on iron absorption in the absence and presence of AA (0, 42.5, and 85 mg/test meal) from a casein/whey-based drink fortified with ferrous sulfate was assessed in a series of randomized crossover studies both in iron-replete (IR) Indian schoolchildren and in children with iron deficiency anemia (IDA) (6-11 y; n = 14-16/group) by using stable isotopes.
  
  
  RESULTS
  In the absence of calcium and AA, iron absorption from the casein/whey-based drink was 20% lower in IR children than in children with IDA. The addition of calcium reduced mean iron absorption by 18-27%, with the effect being stronger for high added calcium (P < 0.01). AA at a 2:1 or 4:1 molar ratio enhanced iron absorption by a factor of 2-4 and greatly overcompensated for the inhibitory effect of calcium on iron absorption in a dose-dependent manner (P < 0.001). The dose-response effect tended to be stronger (P < 0.1) in the IDA group, and iron status was of far less influence on iron absorption than the enhancing effect of AA.
  
  
  CONCLUSIONS
  When adding AA to iron-fortified milk products, care should be taken not to provide absorbable iron in excess of needs.
authors.affiliation: Laboratory for Human Nutrition, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland; Departments of Chemistry (Science) and Biochemistry (Medicine), National University of Singapore, Singapore; walczyk@nus.edu.sg.
authors.forename: Thomas
authors.initials: T
authors.lastname: Walczyk
authors.affiliation: Division of Nutrition, St. John's Research Institute, Bangalore, India; and.
authors.forename: Sumithra
authors.initials: S
authors.lastname: Muthayya
authors.affiliation: Laboratory for Human Nutrition, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland;
authors.forename: Rita
authors.initials: R
authors.lastname: Wegmüller
authors.affiliation: Division of Nutrition, St. John's Research Institute, Bangalore, India; and.
authors.forename: Prashanth
authors.initials: P
authors.lastname: Thankachan
authors.affiliation: Unilever Research and Development, Vlaardingen, The Netherlands.
authors.forename: Aafje
authors.initials: A
authors.lastname: Sierksma
authors.affiliation: Unilever Research and Development, Vlaardingen, The Netherlands.
authors.forename: Leon G J
authors.initials: LG
authors.lastname: Frenken
authors.affiliation: Division of Nutrition, St. John's Research Institute, Bangalore, India; and.
authors.forename: Tinku
authors.initials: T
authors.lastname: Thomas
authors.affiliation: Division of Nutrition, St. John's Research Institute, Bangalore, India; and.
authors.forename: Anura
authors.initials: A
authors.lastname: Kurpad
authors.affiliation: Laboratory for Human Nutrition, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland;
authors.forename: Richard F
authors.initials: RF
authors.lastname: Hurrell
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry / Q000493:pharmacokinetics*; D001628:Beverages / Q000032:analysis*; D002118:Calcium / Q000493:pharmacokinetics*; D002364:Caseins / Q000737:chemistry*; D002648:Child; D002664:Child Nutritional Physiological Phenomena; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004347:Drug Interactions; D005260:Female; D006801:Humans; D007194:India; D007501:Iron / Q000378:metabolism* / Q000493:pharmacokinetics; D008297:Male; D008894:Milk Proteins / Q000737:chemistry*; D000067816:Whey Proteins
chemical_list: D002364:Caseins; D008894:Milk Proteins; D000067816:Whey Proteins; D007501:Iron; D001205:Ascorbic Acid; D002118:Calcium