An estimated 1.9 billion people are at risk of iodine deficiency, a medical condition that can stunt your brain power. Iodine deficiency – which can be avoided by eating seafood, cereal and cow’s milk (due to iodine in cattle feed) – doesn’t just affect the developing world. Up to one-third of children in Europe are thought to need more iodine in their diets.
Because of this, some argue that we should add iodine to salt or provide it in pill-form to pregnant and breast-feeding women, who need even more of it than everyone else. But would the benefits really be worth the cost?
Iodine is a micronutrient that is essential for the thyroid to produce hormones that are crucial for normal brain and neurological development. If you don’t get enough iodine when you’re a child it can result in intellectual disability. A recent national survey demonstrated mild to moderate iodine deficiency in the UK and important observational evidence has linked mild to moderate iodine deficiency to lower IQ scores in UK school children.
Pregnant women need more
Pregnant and breast-feeding women in particular need higher levels of iodine because they produce more thyroid hormones, transfer more iodine to their foetus and in breastmilk, and lose more through urination. Yet an estimated two-thirds of pregnant women in Europe don’t consume enough and regional surveys have confirmed mild to moderate iodine deficiency in UK pregnant women.
This is why the World Health Organisation advocates adding iodine to salt. However, European households are cutting the amount of salt they add to food (in the UK salt added to food represents only about 15% of all salt consumed).
An alternative solution is to give pregnant women iodine tablets. Indeed, many prenatal vitamin-mineral supplements already contain iodine. Yet there is no current UK guidance recommending iodine supplementation in pregnancy and the NHS-prescribed “Healthy Start” vitamins do not contain the nutrient.
My colleagues and I recently examined how the costs of giving women iodine pills during pregnancy weighed against the benefits. We carried out a systematic review of the available evidence and then used that to build a mathematical model that calculated how much iodine pregnancy supplements would boost children’s IQ ratings and the money this would save.
We found that giving iodine to pregnant women could potentially boost the IQ of their children by an average of 1.22 points. This might not seem very much on an individual basis, but across the whole population it would significantly raise the intellectual ability of a large number of children with special needs. Because these children’s additional needs would be reduced, the policy would save the NHS an average of £199 per pregnant woman. Wider societal savings – such as better educational achievement leading to higher incomes in later life – were even higher, at about £4,476 per woman.
There are risks to iodine supplementation, namely thyroid dysfunction. However, we calculated the cost of this problem would need to be more than £91,000 per woman affected to cancel out the overall benefits.
It is important to realise that the predictions are only as reliable as the studies that contributed data. We did not investigate whether iodine supplements in pregnancy boost a child’s IQ ourselves but assumed the fact based on previous observational research. While there is compelling evidence that iodine supplementation improves child IQ in areas of severe iodine deficiency, there is currently no trial evidence for mild-to-moderate deficient populations. However, we took a conservative approach to estimating the benefits and overestimated the potential harms, meaning the IQ and cost gains may be even greater than predicted.
Iodine tablets do have their drawbacks. Pregnancy supplements often do not reach poorer, less educated women (unlike adding nutrients to salt). And as most women only become aware they are pregnant several months after conception, they are unlikely to take tablets during the early stages when the developing fetal brain is especially vulnerable.
Overall, our study has to be considered alongside other research but it provides compelling evidence that iodine supplementation for pregnant women in the UK is potentially cost saving. And, importantly, it has implications for the 1.9 billion people in the 32 countries with iodine deficiency worldwide.