Monday August 10 2015
Iodine can be found in seaweed and cow's milk
"Providing pregnant women with iodine supplements could boost children’s intelligence and save thousands of pounds in future health costs," The Daily Telegraph reports.
Iodine is a chemical element found in seawater, rocks and some types of soil. Good food sources include sea fish and shellfish.
Iodine is important for healthy brain development and there is some evidence that UK women might not be getting enough iodine.
This study modelled how the costs of giving women iodine pills during pregnancy – something that is not currently recommended in England – weighed up against the benefits.
It found that giving iodine to pregnant women could potentially boost the IQ of infants by 1.22 IQ points and save the NHS £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.
These are all estimates that are only as reliable as the data used to inform them, which in this case may have some errors. For example, the effects of iodine on children’s IQ came from three observational studies, which cannot prove cause and effect.
There is no current recommendation in the UK to take iodine supplements during pregnancy, and you should be able to get all the iodine you need by eating a varied diet.
If you do choose to take iodine supplements, do not take more than 0.5mg (milligrams) a day, as this could be harmful.
Where did the story come from?
The study was carried out by researchers from the University of Birmingham and the National University of Singapore, and received no financial support.
The study was published in the peer-reviewed medical journal The Lancet – Diabetes & Endocrinology.
The Daily Telegraph, BBC News and The Independent headlines highlighted the potential benefits of iodine pills to babies and the NHS purse. By contrast, the Daily Mail’s headline focused purely on the potential brain boost to the baby. The study itself did not investigate whether iodine supplements in pregnancy boost a child’s IQ. This was assumed based on previous research – not reviewed here – before being fed into a model estimating the impact of giving iodine to iodine-deficient pregnant women.
There are no new official UK recommendations to take iodine supplements during pregnancy.
What kind of research was this?
This was a systematic review feeding into an economic evaluation aiming to look at how the costs of iodine supplementation for pregnant women weigh up against the benefits.
Previous research is said to have demonstrated that mild to moderate iodine deficiency is quite widespread during pregnancy and may be associated with reduced cognitive (thinking) ability in the child. As the study authors say, reduced intelligence may cost a person and wider society, as it potentially influences educational attainment, future income and wellbeing.
The UK does not currently recommend iodine supplements during pregnancy. Neither does the UK fortify any food substances or salt with iodine, as an increasing number of other countries are said to do. The researchers in this study aimed to look at the cost-effectiveness of iodine supplements compared with no supplements for pregnant women with mild to moderate iodine deficiency.
What did the research involve?
This study fed past research data on iodine deficiency in pregnant women and its effects on the child into a newly-built mathematical model. It used this to predict the likely effect of giving women iodine pills during pregnancy to address the deficiency. It predicted the effect on the child’s intelligence – measured by IQ score, the cost impact to the NHS, and the cost impact to wider society.
The model was based on a range of assumptions derived from previous research, namely that:
- lower IQ leads to lower income (systematic reviews and expert opinion)
- iodine deficiency in pregnant women lowers child IQ (three cohort studies)
- iodine deficiency is relatively common in UK women (one cohort study)
The model considered adverse effects linked to excess iodine, principally thyroid problems, such as overactive thyroid (hyperthyroidism) in the mother.
Costs of supplementation were from a UK perspective. In one analysis, they just looked at direct healthcare costs. In their second analysis, they considered the societal perspective – for example, looking at the cost of education and of increasing the IQ of the child.
What were the basic results?
Overall, the model predicted that giving iodine supplementation to address iodine deficiency in pregnant women would be beneficial, compared to not giving supplements.
Looking at overall healthcare costs, iodine supplementation was predicted to save £199 per pregnant woman and to increase the IQ of future infants by around 1.22 IQ points.
Looking at the wider societal perspective, iodine supplementation was predicted to save a lot more – around £4,476 per pregnant woman – for the same 1.22 point IQ boost in each infant.
The lifetime earnings gain from an additional IQ point was predicted to be about £3,297 based on eight studies, but estimates varied a lot between studies, from as low as £1,313 to as high as £11,967.
The researchers estimated that if iodine supplementation caused thyroid dysfunction in a pregnant woman, this would need to cost more than £91,000 to counter the overall benefits arising from supplementing iodine-deficient pregnant women who didn’t see any adverse effects on their thyroid function.
How did the researchers interpret the results?
The researchers conclude: "Iodine supplementation for pregnant women in the UK is potentially cost saving. This finding has implications for the 1.88 billion people in the 32 countries with iodine deficiency worldwide. Valuation of IQ points should consider non-earnings benefits, e.g. health benefits associated with a higher IQ not germane to earnings".
This economic modelling study predicted that giving iodine supplements to pregnant women would save the NHS money and benefit the infant and wider society by boosting their intelligence.
The study has based its analysis on the UK perspective, used systematic searches and expert input to inform the likely health and economic effects of iodine supplementation.
A strong point of the study, as the authors say, is that they used a conservative approach. This meant they limited the possible benefits of iodine supplementation while overestimating the potential harms as much as possible. This suggests that the cost benefits and IQ gains may even be greater.
However, it is important to realise that these predictions are only as reliable as the studies that contributed data – which will never be perfect. For example, information on how iodine deficiency in pregnancy affected IQ loss in the child came from only three observational studies. These could be affected by a range of bias and confounding factors limiting their reliability. This means that predictions about the exact number of IQ points that have been potentially lost by iodine deficiency in the mother could contain some error. Similarly, it is possible that the savings in terms of cost to health and society are not completely accurate. That said, it’s probably the best they could have done with the available data.
For an individual pregnant woman reading this research in the media, cost savings to society are likely to be of limited relevance. Her concern will be for the health of her child and herself. From that perspective, the main point of interest is the assertion that it may increase the child’s IQ by 1.22 IQ points – though this would probably only be if you were iodine-deficient in the first place. You then have to balance this against the potential risks – mainly in terms of iodine function.
You should be able to get all the iodine you need from a healthy, balanced diet. Rich sources include fish and shellfish (though pregnant women need to take care when eating certain types of fish). Eggs, dairy and certain grains are other sources.
There is no current recommendation in the UK to take iodine supplements in pregnancy. It is not known whether this will change in the future. This economic evaluation would need to be considered as a whole alongside other research related to the harms and benefits of supplements.
In the meantime, if you are going to take iodine supplements, it is advised to take no more than 0.5mg a day, as taking more could be harmful.