Iodine is vital to foetal brain development, so let's act now

This is a story of scientific advance and unexpected consequences - and actions we really ought to take now. Before the first phases of industrialised farming in the early 1800s, many people in the UK suffered from a variety of dietary deficiencies. The most important lack was of iodine - although this was not understood at the time, the element itself not being discovered until 1811. Although we need only trace amounts of iodine that are much less than one thousandth of a gram per day, the lack led to visible symptoms and severe mental retardation - the "village idiot" was not a rarity, but all too common.

Some parts of the country were badly affected - "Derbyshire Neck" was a recognised term for goitre (the swelling of the thyroid gland). During the agricultural revolution, farmers started to feed their cattle with all sorts of foodstuffs to eke out their valuable grass and it was discovered, by chance, that seaweed - kelp, which happens to be rich in iodine - was both useful for cattle feed and led to healthier and more productive cattle. Without understanding the "why", farmers across the country started adding kelp to cattle feed simply to improve productivity.

There was an unexpected side-effect as the cattle produced milk with enough iodine largely to eliminate deficiency in the general population, so goitre and the associated developmental problems became largely historical. Once scientists started to understand nutritional issues more fully, iodine was added to cattle feed in a more systematic way, as it still is, and some table salt was supplemented with iodine - "iodised salt".

Fast forward to the more recent past, and there have been several related developments with, this time, negative effects. Most famously, Margaret Thatcher stopped free school milk as Education Secretary. But there have been other, wider, dietary changes with less milk generally being consumed. Iodised salt remains relatively unusual in the UK and, while it is available, you have to seek it out. It is not used in pre-prepared foods as it can cause minor colour changes. At the same time, we have also been consuming less table salt, because, of course, it carries its own health risks.

The overall effect is that in 2013, about two in three women in the UK are not getting enough iodine in pregnancy. While the deficiency is most often mild, and not enough to generate visible symptoms, iodine deficiency during the early stages of foetal brain development has been shown to have measurable, important and permanent effects on the child. A study reported in The Lancet, which followed 1,000 women and their children, found that children of women who were iodine-deficient during pregnancy were more likely to have scores in the lowest quartile for verbal IQ at age eight and reading comprehension at age nine. There is also evidence of a link between iodine deficiency in early pregnancy and autism. The unfortunate problem with iodine, as opposed to, for example, folic acid, is that it isn't effective if given as a supplement once a woman is pregnant, as it takes several months for the thyroid gland to process enough iodine for normal foetal development.

We urgently need, then, a universal iodine supplement. The cost would be minuscule - 2p per person per year - compared against potentially two-thirds of the children in the country having permanently impaired mental abilities. The World Health Organisation recommends adding iodine to salt as a "spectacularly simple, universally effective, wildly attractive and incredibly cheap technical weapon against the main cause of preventable brain damage and reduced IQ in children worldwide", with about two billion people with some deficiency.

Mass public health interventions can be controversial - fluoridisation is still not universal, although areas that are supplied with fluoridated water have better dental health, and there is little local dissatisfaction with water quality whether it is fluoridised or not. Politically, there seems to be little appetite for taking any positive action on public health, even where the evidence is strong. In recent weeks, the government, scandalously, has shelved plans for minimum pricing of alcohol and for plain packaging of cigarettes.

Public Health England ought to be campaigning for the universal iodisation of table salt. It says: "We work with national and local government, industry and the NHS to protect and improve the nation's health and support healthier choices." Well let's see some action.

John Freeman CBE is a former director of children's services and is now a freelance consultant Read his blog.