Iodine status of teenage girls on the island of Ireland

Abstract

The trace element iodine is a vital constituent of thyroid hormones. Iodine requirements increase during pregnancy, when even mild deficiency may affect the neurocognitive development of the offspring. Urinary iodine concentration (UIC) is the means of assessing iodine status in population surveys; a median UIC of 100-199 µg/L is deemed sufficient in a non-pregnant population. Milk is the main dietary source of iodine in the UK and Ireland. Methods We surveyed the iodine status of 903 girls aged 14-15 years in seven sites across the island of Ireland. Urine iodine concentration was measured in spot-urine samples collected between March 2014 and October 2015. Food group intake was estimated from iodine-specific food-frequency questionnaire. Milk iodine concentration was measured at each site in summer and winter. Results The median UIC overall was 111 µg/L. Galway was the only site in the deficient range (median UIC 98 µg/L). All five of the Republic of Ireland sites had UIC ≤105µg/L. In the two sites surveyed twice, UIC was lower in summer vs winter months (117 µg/L (IQR 76-165) vs 130 µg/L (IQR 91-194) (p<0.01)). Milk samples collected from Galway and Roscommon had a lower mean iodine concentration than those from Derry/Londonderry (p<0.05). Milk intake was positively associated with UIC (p<0.001). Conclusions This is the largest survey of its kind on the island of Ireland, which currently has no iodine fortification programme. Overall, the results suggest that this young female population sits at the low end of sufficiency, which has implications if, in future, they enter pregnancy with borderline status.

What is the availability of iodised salt in supermarkets on the Island of Ireland?

“…Neither the UK nor Ireland has ever had a salt iodisation policy, with dietary iodine relying heavily on adventitious intakes, particularly from dairy produce where presence of iodine in cleaning solutions or in animal feed has historically led to iodine entering milk and dairy produce (2,3). Without any iodised salt policy, a number of studies have investigated iodine intake and status in UK and Irish populations, suggesting some concern (4)(5)(6)(7)(8). This against a background where there has been a rise in non-dairy milk alternatives which may not contain iodine (9).…”

Is There an Ideal Diet to Protect against Iodine Deficiency?

“…Mullan et al also reported that concentration of iodine in milk is higher in the winter than in the summer. Additionally, urinary iodine concentration among girls was lower in summer than winter and was positively correlated with milk consumption [53]. In fact, there are differences between iodine concentrations in milk between various regions in the winter and in the summer which suggest that iodine concentration is dependent on feeding [54].…”

Iodine status in UK–An accidental public health triumph gone sour

“…Cow's milk intake has been in decline over the last 50 years and intake amongst females women, children and teenagers is especially low 18,19,28,53 . A consistent dose‐dependent relationship has been demonstrated between iodine status and milk and dairy intake among females teenage girls in the UK 18,19 . The WHO recommends an intake of 250 µg iodine in pregnancy and one pint of cow's milk (560 mL) equates to approximately 140–224 µg of iodine (Figure 1).…”

“…The SACN in their 2014 position paper noted that teenage girls, milk and fish avoiders and vegans may be at particular risk of iodine deficiency 16 . In 2015, an all‐Ireland survey of 900 teenage girls demonstrated a levels in the low sufficiency range mUIC of 111 μg/L 19 . The most recent UK National Diet and Nutrition Survey (NDNS) based on 2016–2018 data found that the mUIC for women aged 16–49 years ( n = 426) was borderline normal at 102 µg/L with 17% of that population <50 µg/L 20 .…”