Writing in the journal Public Health Nutrition, researchers from Mount Sinai, Tufts University, University of Michigan, Harvard Medical School and Emory University examined associations between prenatal dietary and supplemental iodine intake and infant temperament in a multiethnic group of U.S. women.
“Infant temperament may have long-term consequences for development, including influencing later personality and social skills development and risk for emotional and behavioral problems,” they wrote.
“Identifying risk and protective factors that are readily amenable to intervention such as optimizing prenatal nutritional intake of essential micronutrients such as iodine can inform prevention strategies.”
The study, supported with funding from the National Institutes of Health, extracted 2011 to 2020 data from the PRogramming of Intergenerational Stress Mechanisms (PRISM) study, an ongoing longitudinal pregnancy cohort.
A growing public health issue
The researchers identify inadequate iodine intake as a growing public health issue in the United States and other industrialized countries—partially attributable to modern diet and food manufacturing practices.
“Data from the U.S. National Health and Nutrition Examination Survey (NHANES) 2005–2010 reported a median urinary iodine concentration (UIC) of 129 μg/l in pregnant women, significantly lower than in 2001–2006,” they noted. “Non-Hispanic Black pregnant women were particularly likely to have iodine levels below 150 µg/l, the median UIC for pregnant women recommended by the World Health Organization (WHO).”
Not only is iodine a key component of thyroid hormones, which regulate brain and nervous system development, but suboptimal iodine levels during gestation contribute to oxidative stress, disturbing the placental redox balance optimal to fetal development.
The study also references a recent scoping review of epidemiological studies reporting mixed results in associations between iodine and child neurodevelopment in Europe, India, Japan and Scandinavian countries but highlighted that similar studies in U.S. infants are sparse, particularly among racially/ethnically diverse women and children.
“Moreover, many neurodevelopmental outcomes including temperament present with a sex or gender bias,” they added. “Given the focus herein on prenatal neuro-programming, we conceptualize influences of biological sex rather than the social construct of gender.”
Study details
The researchers analyzed 2011 to 2020 data from 892 mother-child pairs recruited from an urban sample of women and children.
Women were primarily Black/Hispanic Black (44%) and non-Black Hispanic (35%), with 46% reporting household income under $25,000 a year.
Participants completed a validated dietary assessment of prenatal dietary and supplemental iodine intake and the Infant Behavior Questionnaire at six months to determine infant temperament (surgency/extraversion, negative affectivity and orienting/regulation).
“We found that nearly half of these women reported iodine intake during pregnancy below the EAR of ≥ 160 µg/d whether based on dietary intake (49%) or when food and supplements were considered together (43%), similar to recent estimates reported in another U.S. cohort of pregnant women finding that 41% remained below the EAR even after supplementation,” the researchers reported.
Findings indicated that girls born to women with an EAR of 160 µg/d or over had higher extraversion scores (sociability and how well they interact with others) than girls born to women below this level.
In addition, the study highlighted that prenatal iodine intake from diet plus supplements at or exceeding an EAR ≥ 160 µg/d was associated with lower negative affectivity scores (characterized by feelings of calmness, serenity, confidence and enthusiasm) after adjusting for covariates, particularly among boys.
“Measures of infant negative affectivity show similarity to measures of negative affectivity in older children and to the adult personality factor of neuroticism, suggesting that negative affectivity may be relatively stable across the life course,” the researchers wrote.
“Thus, explicating factors that shape negative affectivity may inform our understanding of the earliest origins of mental health risk, resilience and other developmental outcomes.”
The study called for additional research to explore inconsistencies across the findings to date before clinical recommendations can be made based on child neurodevelopmental outcomes.
Source: Public Health Nutrition
doi: 10.1017/S1368980024001575
“Prenatal iodine intake and infant temperament in a multiethnic US cohort”
Authors: Aderonke Akinkugbe et al.
