Turkish researchers have advised iodine-deficient pregnant women to take 100–200 micrograms (μg) per day of iodine-containing supplements in addition to iodised salt after their research revealed still high levels of deficiency despite mandatory iodisation of table salt.
“Our study demonstrates that, although the iodine status among school-age children has been rectified, iodine deficiency is still prevalent among pregnant women. Current knowledge is in favour of iodine supplementation in this group,” they wrote in the British Journal of Nutrition.
The study focused on Trabzon, an area classed as ‘severely iodine-deficient’ back in 1997.
Mandatory iodisation of table salt was introduced in the country in 1999 and according to a 2007 study in school-age children the area is now ‘iodine sufficient’.
However studies regarding iodine status in pregnant women were limited and those that had been carried out in Turkey were local with small samples.
Therefore the researchers from the Trabzon Kanuni Education and Research Hospital, Karadeniz Technical University and Ankara University in Turkey sought to examine the impact on pregnant women specifically.
They included 864 healthy pregnant women with an average age of 28, none of whom were using iodine supplements.
Iodine is essential for thyroid hormone synthesis and neurological development and changes to metabolism during pregnancy means these women require greater levels.
Last year the European Food Safety Authority (EFSA) proposed intake levels of 200 micrograms (µg) for pregnant and lactating women compared to 150 µg for adults more generally.
This was lower than the World Health Organisation’s (WHO) recommendations of a daily intake of 150 μg for non-pregnant women and 250 μg for pregnant and lactating women.
Meanwhile in the UK the Reference Nutrient Intake for adults is 140 μg day, without any suggested increase for pregnant and lactating women.
According to the World Health Organisation (WHO) iodine deficiency is the world’s most prevalent, yet easily preventable, cause of brain damage.
The number of countries where iodine deficiency is a public health problem has halved over the past decade, in part due to salt iodisation programmes.
However 54 countries are still iodine-deficient.
In this latest study the rate of use of the iodised salt among the women was 90.7%.
The women were screened for thyroid function and urinary iodine concentrations and thyroid ultrasonographies were conducted.
The average urine concentration was 102 μg/l, with the 25th–75th percentile ranging from 62–143 μg/l.
Average urinary iodine concentrations according to trimesters were 122 μg/l in the first, 97 μg/l in the second and 87 μg/l in the third trimester.
To supplement or not to supplement
However a paper from Chinese researchers in September urged caution when it came to advising pregnant women to up iodine intakes.
They found the prevalence of thyroid disease in lactating women, particularly subclinical hypothyroidism (or an 'underactive thyroid gland'), was significantly higher in those with excess iodine intakes compared to those living in the areas with lower levels of the trace element in the water.
The paper built on a 2009 Korean research paper.
EFSA has authorised five health claims for iodine covering ‘normal thyroid function and production of thyroid hormones’, ‘maintenance of skin’, ‘normal cognitive and neurological function’, ‘normal energy-yielding metabolism’ and ‘normal growth of children’.
Source: British Journal of Nutrition
Published online ahead of print, doi:10.1017/S0007114515004559
“Iodine status among pregnant women after mandatory salt iodisation”
Authors: İ. Anaforoğlu1, E. Algün, Ö. İnceçayır, M. Topbaş and M. F. Erdoğan