Northern Irish women have only half the recommended iodine levels at critical stage of pregnancy

Pregnant Northern Irish women do not get enough iodine through their diet and do not know enough about how to address their deficiency, according to preliminary research presented today at the Society for Endocrinology annual conference in Brighton. The researchers call for better public health initiatives to advise women on optimising their iodine intake in pregnancy.

Iodine is an essential nutrient needed to make thyroid hormones, which control the body’s metabolism and growth. In the UK, dairy products are the primary source of iodine, but egg yolks and seafood are other good sources. Thyroid hormones also play a critical part in normal brain development of the foetus, and up until the second trimester of pregnancy, babies cannot make any of their own thyroid hormones and are reliant on the mother to provide for them. If a mother is seriously deficient in iodine and thyroid hormones, the unborn baby may be at risk of life-changing complications, including low IQ and stunted physical growth. Other studies suggest that even mild maternal iodine deficiency is associated with lower intellect and reading ability in offspring. Previous work has shown that Northern Ireland had the lowest iodine intake of the UK.

In this study, researchers from the Royal Victoria Hospital in Belfast monitored iodine levels in the urine of 241 women in Northern Ireland throughout pregnancy. During the first trimester, a critical time in foetal development, the median iodine concentrations were 72µg/L, less than half the 150µg/L recommended by the World Health Organisation (WHO). Although iodine levels increased throughout the pregnancy, they were consistently lower than recommended. The study also found that women were not getting adequate iodine intake in their diets, with an average of 133µg/day consumed out of the minimum of 250µg/day recommended by WHO.

The study also investigated a separate group of 183 women in order to assess how aware they were of iodine importance in pregnancy. When interviewed, only 5% of women felt they had adequate knowledge about iodine and only 10% were aware that dairy products were a good source.

“Our study suggests that pregnant women living in Northern Ireland are iodine deficient and have not been provided with the knowledge to improve this,” said Dr Paul McMullan, lead researcher of the study.

“Pregnant women are warned about the dangers of folic acid deficiency and foetal development but few appear to be aware of the effect of iodine deficiency. 90% of the women we interviewed felt informed about folic acid whilst only 5% had knowledge regarding iodine.”

“Although levels in the infants of this study were adequate, probably due to concentrating ability of iodine in breast milk and adequate levels in formula feed, the impact of low levels at the start of pregnancy, when brain and nerve health is most critical, is uncertain and therefore of concern.” 

This study is in line with a series of other studies which show mild iodine deficiency in pregnant women in various regions of the UK.

“Iodine deficiency is common in many countries. In the US, Canada and Australia food iodine fortification programs have been implemented, where iodine is added to table salt. At the very least we should advise women living in the UK how to optimise their iodine status in pregnancy by increasing their intake of iodine rich foods or using an iodine supplement”, said Dr McMullan.