Can the low content of iodine and selenium in vegetarian and vegan food adversely affect thyroid function in pregnant women and impair development of their children?

Research Project, 2020 – 2022

Scandinavian soil and foods are low in iodine and selenium, both of which are critical for thyroid hormone production and fetal development. Even moderate deficiency in pregnancy may cause impairments. Especially vegetarian and vegan diets contain very low levels, and also multiple goitrogenic (anti-thyroid) food items, such as soy beans. Iodine-fortified salt, introduced in 1936 to eradicate prevalent deficiency and goiter, is still the main iodine source; but the use is decreasing. A recent study on iodine status in pregnant women in Värmland and Uppsala revealed median urinary iodine concentrations (UIC) of 98 µg/L, i.e. far below adequate UIC of 150-250 µg/L (WHO) for pregnant and lactating women. Preliminary data from the new Swedish mother-child cohort NICE indicates prevalent deficiency of both iodine and selenium in pregnancy. This 3-year project concerns further assessments of the pregnant women in NICE (delivered at Sunderby hospital in Norrbotten; n=655) and their children. We aim to clarify i) gestational and child status of iodine (UIC and breast milk) and selenium (blood) and the main dietary sources, ii) the impact on thyroid hormones (in pregnancy and infancy), and iii) fetal and infant growth and neurodevelopment (cognition, behavior) at 4 years. Detailed dietary intake data (incl. type of salt) in pregnancy and infancy is obtained via repeated questionnaires. The results are vital for evaluating needs of dietary recommendations and new products.