A new study published in The Journal of Nutrition provides further evidence that all women who could become pregnant, who are pregnant, or who are breastfeeding will benefit from a daily multivitamin-mineral supplement.

Iodine is essential to produce thyroid hormones, which are required for normal growth and brain development of the fetus and infant. Contributing to a limited body of literature on iodine status of mother-infant dyads, Dr. Jesse Bertinato (Health Canada) and co-authors assessed the iodine status of 132 mother-infant pairs.

The percentages of mothers that used a multivitamin-mineral supplement containing iodine were 90% in pregnancy and 79% and 59% at 1 and 6 months of lactation, respectively.  At 1 month of age, 99% of the infants were breastfed, with 70% exclusively breastfed. None of the infants <12 months of age consumed an iodine supplement. Maternal iodine status was assessed using the breastmilk iodine concentration. Iodine intakes of infants from 1–36 months of age were estimated from urinary iodine and creatinine (a measure of kidney function and urine dilution) concentrations.

Breastmilk iodine concentrations in the first month of lactation indicated adequate maternal iodine status but these concentrations declined substantially by the sixth month of lactation. The decline in maternal iodine status coincided with declining supplement use. Iodine status of infants were adequate throughout infancy, indicating sufficient iodine intakes from breastmilk during the first few months of breastfeeding. In older infants, appropriate complementary feeding practices helped meet iodine requirements. Because most pregnant and lactating women do not meet iodine requirements, these results reinforce recommendations that all pregnant and lactating women in North America take a multivitamin-mineral supplement containing iodine.


Jesse Bertinato, Jeremiah Gaudet, Nimal De Silva, Smitarani Mohanty, Cunye Qiao, Matthew Herod, Nathalie Gharibeh, Hope Weiler, Iodine Status of Mother-Infant Dyads from Montréal, Canada: Secondary Analyses of a Vitamin D Supplementation Trial in Breastfed Infants, The Journal of Nutrition, Volume 152, Issue 6, June 2022, Pages 1459–1466, https://doi.org/10.1093/jn/nxac047.

Images via canva.com.