Q&A: Iodine deficiency
Research has warned that many pregnant women in the UK are not getting enough iodine in their diet.
Mothers who were deficient had children with a slightly lower IQ and worse reading scores in primary school.
Why do we need iodine?
It is a building block of hormones made in the thyroid gland. These control the way the body uses energy and how it grows. It is particularly important when the brain is developing.
Why is it an issue in pregnant women?
In pregnancy you need 50% more of the chemical than normal. This is because the thyroid needs to build enough hormones for both you and the foetus in early pregnancy. Once the foetus's own thyroid is up and running, it still needs iodine, which can come only from the mother's diet. After birth, the iodine will come from breast milk.
How common is deficiency?
The study showed that two in three women were not getting enough iodine during pregnancy. This was mostly mild deficiency.
So where do I get it from?
In the UK the main source of iodine is milk. Other dairy products and fish are also great sources of iodine. It is also in some vitamin and mineral supplements. Advice has been published on the British Dietetic Association website, but the researchers said two portions of fish a week and three portions of milk or other dairy products a day would be enough. The Department of Health says a balanced diet during pregnancy would contain enough iodine.
Can I have too much?
Yes. Taking too much can cause thyroid problems. It is why the researchers do not advise taking seaweed or kelp supplements as these contain "excessive" levels.
What about salt?
Iodine deficiency is a big global problem. The World Health Organization recommends adding iodine to salt as it is a "spectacularly simple, universally effective, wildly attractive and incredibly cheap technical weapon".
So why doesn't the UK add iodine to salt?
The UK thought it had fluked the solution. Changes to dairy farming practice, such as adding iodine to cow feed, meant the major deficiency problems witnessed up to the 1960s had pretty much disappeared. A decision to add iodine to salt is not on the cards in the UK despite growing awareness of the problems of mild deficiency. Such public health interventions are often controversial - think of the vocal opposition to adding fluoride to water in order to improve dental health.