Breast Milk Iodine Concentration Is Associated with Infant Growth, Independent of Maternal Weight

Abstract

In breastfed infants, human milk provides the primary source of iodine to meet demands during this vulnerable period of growth and development. Iodine is a key micronutrient that plays an essential role in hormone synthesis. Despite the importance of iodine, there is limited understanding of the maternal factors that influence milk iodine content and how milk iodine intake during infancy is related to postnatal growth. We examined breast milk samples from near 2 weeks and 2 months post-partum in a mother-infant dyad cohort of mothers with pre-pregnancy weight status defined by body mass index (BMI). Normal (NW, BMI < 25.0 kg/m2) is compared to overweight/obesity (OW/OB, BMI ≥ 25.0 kg/m2). The milk iodine concentration was determined by inductively coupled plasma mass spectrometry. We evaluated the associations between iodine content at 2 weeks and infant anthropometrics over the first year of life using multivariable linear mixed modeling. Iodine concentrations generally decreased from 2 weeks to 2 months. We observed no significant difference in iodine based on maternal weight. A higher iodine concentration at 2 weeks was associated with a larger increase in infant weight-for-age and weight-for-length Z-score change per month from 2 weeks to 1 year. This pilot study shows that early iodine intake may influence infant growth trajectory independent of maternal pre-pregnancy weight status.

Iodine status of postpartum women and their infants aged 3, 6 and 12 months: Mother and Infant Nutrition Investigation (MINI)

“…[85 (43,134)µg/L] and 12MPP [95 (51,169)µg/L] < 100µg/L. The use of iodine-containing supplements increased MUIC and BMIC only at 3MPP.…”

“…This study found that maternal supplementation is more effective in ensuring adequate infant iodine status and maintaining BMIC levels until at least six months postpartum 42 . Achieving adequate maternal iodine status throughout lactation is critical for infants' growth 43 and also optimal fetal neurodevelopment 44 .…”

Is breast milk iodine concentration an influential factor in growth‐ and obesity‐related hormones and infants' growth parameters?

“…Despite the best criteria for assessing an infant's iodine status have not been established due to the difficulty of sample collection for urinary iodine in this age group, there is sufficient data suggesting that the iodine status of infants could be extrapolated from either breast milk or maternal urinary iodine concentrations (Dold et al, 2017; Nazeri, Dalili, et al, 2018). In a pilot study by Ellsworth et al, BMIC at 2‐week postpartum was positively associated with infants' weight‐for‐age and weight‐for‐length over the first year of life (Ellsworth, McCaffery, Harman, Abbott, & Gregg, 2020). This finding was similar to our study with a different technique for BMIC measurement.…”

Veganism and paediatric food allergy: two increasingly prevalent dietary issues that are challenging when co-occurring

“…As such, iodine requirements are better met through breastmilk. A recent study found that breastmilk iodine concentrations were not associated with pre-pregnancy weight, although maternal diet was not considered in the analyses [48]. In contrast, the Centers for Disease Control and Prevention advises that the recommended daily allowance is 290 μg iodine for breastfeeding women, and that a supplement is indicated for women who do not consume dairy products [49].…”