Breastfed infants rely on iodine provided by human milk, but the breast milk iodine concentration (BMIC) of lactating women is low in many countries, including Switzerland. Iodine supplementation to lactating women is recommended in populations with inadequate iodine intake, but the scientific evidence is weak and the optimal dose is uncertain. The reference iodine intakes and optimal BMIC in lactating women are poorly defined, making the criteria for iodine deficiency and indications for iodine supplementation during lactation unclear.
Our objectives are to: 1) Define the estimated average requirement (EAR) for iodine in lactating women; 2) Assess the dose-response of iodine supplementation on BMIC in lactating women and estimate the maternal iodine intake required to ensure adequate iodine intake in breastfed infants.
We will conduct a dose-response, balance study in 24 exclusively breastfeeding women and their infants. Three iodine supplement regimens (0, 150, 300 µg/day) will be administered in random order with cross-over design in women with assumed sufficient (n=12) and insufficient (n=12) iodine intakes. We will measure daily iodine intake and excretion in mothers and infants, and calculate the iodine retention for each dose. The daily intake required to achieve positive iodine balance during lactation and infancy will be determined as well as the optimal dose needed to replete iodine deficient intakes in mothers and infants.