Abstract
Breastfed infants are dependent on an adequate supply of iodine in human milk for the production of thyroid hormones, necessary for development of the brain. Despite the importance of iodine for infant health, data on Norwegian lactating women are scarce. We measured iodine intake and evaluated iodine status and iodine knowledge among lactating women. From October to December 2018, 133 mother–infant pairs were recruited in a cross-sectional study through two public health care centers in Lillehammer and Gjøvik. Each of the women provided two human milk specimens, which were pooled, and one urine sample for analysis of iodine concentration. We used 24-h dietary recall and food frequency questionnaire (FFQ) to estimate short-term and habitual iodine intake from food and supplements. The median (P25, P75) human milk iodine concentration (HMIC) was 71 (45, 127) µg/L—of which, 66% had HMIC <100 µg/L. The median (P25, P75) urinary iodine concentration (UIC) was 80 µg/L (52, 141). The mean (± SD) 24-h iodine intake and habitual intake was 78 ± 79 µg/day and 75 ± 73 µg/day, respectively. In conclusion, this study confirms inadequate iodine intake and insufficient iodine status among lactating women in the inland area of Norway and medium knowledge awareness about iodine.
Highlights
Adequate human milk iodine concentration (HMIC) is essential to provide sufficient iodine supply for the infant
We found that the women were mild to moderately iodine deficient, based on suboptimal iodine concentrations in human milk as well as in urine, and inadequate dietary iodine intake according to both habitual and 24-h food and supplement intake
We found that the majority of the women had medium iodine knowledge
Summary
Adequate human milk iodine concentration (HMIC) is essential to provide sufficient iodine supply for the infant. Sufficient iodine intake during infancy is important to ensure optimal thyroid hormone stores and to prevent impaired neurological development [1,2,3,4,5]. Pregnancy is a crucial period for fetal brain development. Adequate iodine supply throughout pregnancy, lactation and the first years of life is a prerequisite for normal neurodevelopment [5,6,7]. In 2018, estimates suggested that up to 50% of newborns in Europe were exposed to iodine deficiency [8], and at risk of not achieving their full intellectual capacity
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