Breast milk iodine and perchlorate concentrations in lactating Boston-area women

J Clin Endocrinol Metab. 2007 May;92(5):1673-7. doi: 10.1210/jc.2006-2738. Epub 2007 Feb 20.


Context: Breastfed infants rely on adequate maternal dietary iodine intake.

Objective: Our objective was to measure breast milk iodine and perchlorate, an inhibitor of iodide transport into the thyroid and potentially into breast milk, in Boston-area women.

Participants: The study included 57 lactating healthy volunteers in the Boston area.

Measurements: Breast milk iodine and perchlorate concentrations and urine iodine, perchlorate, and cotinine concentrations were measured. For comparison, iodine and perchlorate levels in infant formulae were also measured.

Results: Median breast milk iodine content in 57 samples was 155 microg/liter (range, 2.7-1968 microg/liter). Median urine iodine was 114 microg/liter (range, 25-920 microg/liter). Perchlorate was detectable in all 49 breast milk samples (range, 1.3-411 microg/liter), all 56 urine samples (range, 0.37-127 microg/liter), and all 17 infant formula samples (range, 0.22-4.1 microg/liter) measured. Breast milk iodine content was significantly correlated with urinary iodine per gram creatinine and urinary cotinine but was not significantly correlated with breast milk or urinary perchlorate.

Conclusions: Perchlorate exposure was not significantly correlated with breast milk iodine concentrations. Perchlorate was detectable in infant formula but at lower levels than in breast milk. Forty-seven percent of women sampled may have been providing breast milk with insufficient iodine to meet infants' requirements.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Boston / epidemiology
  • Diet
  • Female
  • Humans
  • Infant
  • Infant Food / analysis
  • Infant Nutritional Physiological Phenomena
  • Infant, Newborn
  • Iodine / metabolism*
  • Iodine / urine
  • Lactation / physiology
  • Middle Aged
  • Milk, Human / chemistry*
  • Perchlorates / metabolism*
  • Smoking / metabolism


  • Perchlorates
  • Iodine