Abstract
Iodine and selenium are essential trace elements. Recent studies indicate that pregnant and lactating women often have insufficient intake of iodine and selenium, but the impact on fetal and infant status is unclear. Here, we assessed iodine and selenium status of infants in relation to maternal intake and status of these trace elements in the birth cohort NICE, conducted in northern Sweden (n = 604). Iodine was measured in urine (UIC) in gestational week 29, and in breast milk and infant urine 4 months postpartum, while selenium was measured in maternal plasma and erythrocytes in gestational week 29, and in breast milk and infant erythrocytes 4 months postpartum, in both cases using ICP-MS. Maternal intake was assessed with semi-quantitative food frequency questionnaires in gestational week 34 and at 4 months postpartum. The median intake of iodine and selenium during pregnancy (98 and 40 μg/d, respectively) and lactation (108 and 39 μg/d, respectively) was below recommended intakes, reflected in insufficient status (median UIC of 113 μg/L, median plasma selenium of 65 μg/L). Also, breast milk concentrations (median iodine 77 μg/L, median selenium 9 μg/L) were unlikely to meet infant requirements. Median UIC of the infants was 114 μg/L and median erythrocyte selenium 96 μg/kg, both similar to the maternal concentrations. Infant UIC correlated strongly with breast milk levels (rho = 0.64, p < 0.001). Their erythrocyte selenium correlated with maternal erythrocyte selenium in pregnancy (rho = 0.38, p < 0.001), but not with breast milk selenium, suggesting formation of prenatal reserves. Our results indicate that the transport of iodine and selenium to the fetus and infant is prioritized. Still, it is uncertain whether most infants had sufficient intakes. Further, the results might indicate an involvement of iodine in asthma development during the first year of life, which is essential to follow up. The low maternal and infant dietary intake of both iodine and selenium, especially when the mothers did not use supplements or iodized table salt, suggest a need for a general screening of women and young children.
Highlights
The nutritional needs of the developing fetus are met through transport of nutrients from mother to child via the placenta
We explored associations of iodine and selenium intake and status with allergy outcomes using multivariableadjusted logistic regression models
Higher maternal dietary intake of iodine at 4 months postpartum was significantly associated with lower odds of infant asthma during the first year of life, both in the unadjusted (OR = 0.91, 95% CI: 0.83-0.98) and in the adjusted model (OR = 0.90, 95% CI: 0.82–0.97) (Table 5)
Summary
The nutritional needs of the developing fetus are met through transport of nutrients from mother to child via the placenta. During early infancy, these needs are covered by breast milk or by infant formula. Adequate status of the nutrients iodine and selenium are essential for thyroid function [2, 3]. Impaired thyroid function during pregnancy and lactation has been associated with impaired child growth and neurodevelopment, and in severe cases even increased child mortality [2–6]. Selenoproteins, in which selenium is incorporated, influence a wide range of immune responses [7], and the antioxidative abilities of some of these proteins have, for instance, been suggested to affect asthma risk [8–11]. The role of iodine in allergy development is not yet known, but the sparse evidence suggests that iodine could be involved in immune responses [12]
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