title: The Swiss iodized salt program provides adequate iodine for school children and pregnant women, but weaning infants not receiving iodine-containing complementary foods as well as their mothers are iodine deficient.
abstract: BACKGROUND
  If children and pregnant women in the population are iodine sufficient, it is generally assumed infants are also sufficient. But weaning infants may be at risk of iodine deficiency because iodized salt contributes little dietary iodine during this period. To fill this gap, iodine fortification of infant formula milk (IFM) and complementary foods (CF) is likely important.
  
  
  OBJECTIVE
  The objective of the study was to first confirm that Swiss school children and pregnant women remain iodine sufficient and then to assess iodine status in infancy and the relative contribution of breast milk and IFM/CF to their iodine intakes.
  
  
  METHODS
  We measured urinary iodine concentrations (UIC) in national cross-sectional samples of: 1) pregnant women (n=648); 2) school children (n=916); 3) infants at three time points: at 3-4 d after birth and at 6 and 12 months (n=875); and 4) breast-feeding mothers (n=507). We measured breast milk iodine concentrations in the mothers, assessed iodine sources in infant diets, and analyzed iodine content of commercial IFM/CFs (n=22) and salt samples from the school children's households (n=266).
  
  
  RESULTS
  Median (m) UICs in pregnant women (162 μg/liter) and school children (120 μg/liter) were sufficient, and 80% of the household salt was adequately iodized (≥15 ppm). However, mUICs in infants not receiving IFM/CF were not sufficient: 1) mUIC in breast-fed infants (82 μg/liter) was lower than in non-breast-fed infants (105 μg/liter) (P<0.001) and 2) mUIC in breast-fed weaning infants not receiving IFM/CF (70 μg/liter) was lower than infants receiving IFM (109 μg/liter) (P<0.01). mUIC was low in lactating mothers (67 μg/liter) and median breast milk iodine concentration was 49 μg/kg.
  
  
  CONCLUSIONS
  In countries in which iodized salt programs supply sufficient iodine to older children and pregnant women, weaning infants, particularly those not receiving iodine-containing IFM, may be at risk of inadequate iodine intakes.
authors.affiliation: Human Nutrition Laboratory, Institute of Food, Nutrition, and Health, Swiss Federal Institute of Technology Zürich, Schmelzbergstrasse 7, CH-8092 Zürich, Switzerland.
authors.forename: Maria
authors.initials: M
authors.lastname: Andersson
authors.forename: Isabelle
authors.initials: I
authors.lastname: Aeberli
authors.forename: Nadja
authors.initials: N
authors.lastname: Wüst
authors.forename: Alberta M
authors.initials: AM
authors.lastname: Piacenza
authors.forename: Tamara
authors.initials: T
authors.lastname: Bucher
authors.forename: Isabelle
authors.initials: I
authors.lastname: Henschen
authors.forename: Max
authors.initials: M
authors.lastname: Haldimann
authors.forename: Michael B
authors.initials: MB
authors.lastname: Zimmermann
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007225:Infant Food / Q000032:analysis; D007231:Infant, Newborn; D007455:Iodine / Q000032:analysis / Q000172:deficiency* / Q000494:pharmacology / Q000652:urine; D008895:Milk, Human / Q000737:chemistry; D011247:Pregnancy; D011295:Prenatal Care / Q000592:standards; D017673:Sodium Chloride, Dietary / Q000494:pharmacology*; D013557:Switzerland; D014886:Weaning
chemical_list: D017673:Sodium Chloride, Dietary; C034024:iodized salt; D007455:Iodine