Iodine deficiency in the UK: an overlooked cause of impaired neurodevelopment?

Abstract

This review describes historical iodine deficiency in the UK, gives current information on dietary sources of iodine and summarises recent evidence of iodine deficiency and its association with child neurodevelopment. Iodine is required for the production of thyroid hormones that are needed for brain development, particularly during pregnancy. Iodine deficiency is a leading cause of preventable brain damage worldwide and is associated with impaired cognitive function. Despite a global focus on the elimination of iodine deficiency, iodine is a largely overlooked nutrient in the UK, a situation we have endeavoured to address through a series of studies. Although the UK has been considered iodine-sufficient for many years, there is now concern that iodine deficiency may be prevalent, particularly in pregnant women and women of childbearing age; indeed we found mild-to-moderate iodine deficiency in pregnant women in Surrey. As the major dietary source of iodine in the UK is milk and dairy produce, it is relevant to note that we have found the iodine concentration of organic milk to be over 40 % lower than that of conventional milk. In contrast to many countries, iodised table salt is unlikely to contribute to UK iodine intake as we have shown that its availability is low in grocery stores. This situation is of concern as the level of UK iodine deficiency is such that it is associated with adverse effects on offspring neurological development; we demonstrated a higher risk of low IQ and poorer reading-accuracy scores in UK children born to mothers who were iodine-deficient during pregnancy. Given our findings and those of others, iodine status in the UK population should be monitored, particularly in vulnerable subgroups such as pregnant women and children.

Maternal Hypothyroxinemia-Induced Neurodevelopmental Impairments in the Progeny

“…Although fortification of bread with iodized salt just increased median urinary iodine concentrations (UIC) to 84 μg/L, this level was outside the World Health Organization's (WHO) criterion of adequate iodine (150-249 μg/L). A review focusing on iodine deficiency in the UK found that mild to moderate iodine deficiency existed among pregnant women in some regions and concluded this may be a cause for impaired neurodevelopment seen in some children [35]. Alarmingly, the re-emergence of iodine deficiency in developed countries, such as the UK, USA, and Australia, is concerning and warrants our increased attention.…”

Iodide transport: implications for health and disease

“…Importantly, pregnant women need higher amounts of iodide (Table 1). Even mild iodine deficiency during pregnancy may affect outcomes [54,59-61]. However, despite the efforts from the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) to end a preventable form of hypothyroidism, goiter and mental retardation, thirty-two countries and about 246 million schoolchildren are estimated to have insufficient iodine intake [4,5].…”

Maternal Different Degrees of Iodine Deficiency during Pregnant and Lactation Impair the Development of Cerebellar Pinceau in Offspring

“…While, it is worth noting that there are a large number of women of child bearing age in the situation of marginal ID, with the UIC of 100–150 μg/l (Ferreir et al, 2014; Méndez-Villa et al, 2014). Furthermore, even in developed countries, the pregnant women are still in the situation of mild to moderate ID (Bath and Rayman, 2013; Clifton et al, 2013). Therefore, it is necessary to screen the thyroid function and adequate iodine supplementation during pregnancy and lactation, which may reduce the risk of neurodevelopmental delay and cognitive and psychomotor dysfunction in the fetus or infants.…”