A study of 122 breastfeeding moms found that the amount of IGF-1 in early breast milk did not affect their kids' brain, language, or motor skills at age three, and higher iodine levels were oddly linked to slightly lower cognitive scores.

This study targeted to investigate the potential role of breast milk iodine concentration (BMIC), insulin-like growth factor-1 (IGF-I), and brain-derived neurotrophic factor (BDNF) during the early stage of lactation in child neurocognitive development. In this secondary analysis, we examined 122 breastfeeding mothers and their healthy children, all of whom were breastfed for at least six months. Levels of BDNF, IGF-1, and BMIC were assessed in breast milk samples obtained between the third and fifth days after lactation began (before any iodine supplementation intervention). Three-year-old children were administered the Bayley-III screening test to assess their cognitive, motor, and language development. The median (interquartile range) concentrations of iodine, BDNF, and IGF-1 in breast milk during the starting few days of lactation were 285.0 (181.0-366.0) &#x3bc;g/l, 0.59 (0.52-0.76) ng/ml, and 12.5 (9.6-18.3) ng/ml, respectively. The mean (standard deviation) cognitive, motor, and language scores were 101.0 (10.8), 93.4 (14.6), 100.1 (13.5) and, respectively. Linear regression models revealed a negative relation between breast milk iodine and children's cognitive development ((&#x3b2; unadjusted = -0.004 (<i>P</i> = 0.010); &#x3b2; adjusted = -0.003 (<i>P</i> = 0.024)). However, no associations were found between breast milk BDNF and IGF-1 and cognitive, language, or motor scores in three-year-olds. Our findings indicate that early exposure to iodine, BDNF, and IGF-1 in breast milk, measured prior to iodine supplementation, has no substantial association with neurodevelopment in three-year-old children. The weak negative association between BMIC and cognitive scores may reflect prenatal iodine status, warranting further research to explore long-term effects of supplementation.