title: The relationship between cow's milk and stores of vitamin D and iron in early childhood.
abstract: OBJECTIVE
  To examine the association between cow's milk intake on both vitamin D and iron stores in healthy urban preschoolers.
  
  
  METHODS
  Healthy children 2 to 5 years of age were recruited from December 2008 through December 2010 through the TARGet Kids! practice-based research network. Cow's milk intake was measured by parental report. Vitamin D and iron stores were measured by using serum 25-hydroxyvitamin D and ferritin. Bivariate multivariable linear regression was used to examine the effect of cow's milk intake simultaneously on 25-hydroxyvitamin D and serum ferritin. Analyses were stratified by important clinical variables including skin pigmentation, bottle feeding, vitamin D supplementation, and season.
  
  
  RESULTS
  Among 1311 children, increasing cow's milk consumption was associated with decreasing serum ferritin (P < .0001) and increasing 25-hydroxyvitamin D (P ≤ .0001). Two cups (500 mL) of cow's milk per day maintained 25-hydroxyvitamin D >75 nmol/L with minimal negative effect on serum ferritin for most children. Children with darker skin pigmentation not receiving vitamin D supplementation during the winter required 3 to 4 cups of cow's milk per day to maintain 25-hydroxyvitamin D >75 nmol/L. Cow's milk intake among children using a bottle did not increase 25-hydroxyvitamin D and resulted in more dramatic decreases in serum ferritin.
  
  
  CONCLUSIONS
  There is a trade-off between increasing 25-hydroxyvitamin D and decreasing serum ferritin with increasing milk intake. Two cups of cow's milk per day appears sufficient to maintain healthy vitamin D and iron stores for most children. Wintertime vitamin D supplementation was particularly important among children with darker skin pigmentation.
authors.affiliation: The Applied Health Research Centre of the Li Ka Shing Knowledge Institute of St Michael’s Hospital, University of Toronto, Toronto, Ontario, Canada. jonathon.maguire@utoronto.ca
authors.forename: Jonathon L
authors.initials: JL
authors.lastname: Maguire
authors.forename: Gerald
authors.initials: G
authors.lastname: Lebovic
authors.forename: Sharmilaa
authors.initials: S
authors.lastname: Kandasamy
authors.forename: Marina
authors.initials: M
authors.lastname: Khovratovich
authors.forename: Muhammad
authors.initials: M
authors.lastname: Mamdani
authors.forename: Catherine S
authors.initials: CS
authors.lastname: Birken
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Parkin
mesh_terms: D000818:Animals; D002417:Cattle; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D005293:Ferritins / Q000097:blood*; D006801:Humans; D007501:Iron / Q000097:blood*; D008297:Male; D008892:Milk / Q000378:metabolism*; D012880:Skin Pigmentation / Q000502:physiology*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; D005293:Ferritins; C104450:25-hydroxyvitamin D; D007501:Iron