The UK population may now be iodine-deficient, warranting a full review and evidence-based recommendations to safeguard public health, according to new research.
Iodised salt has helped to reduce iodine deficiency globally, but is not currently used in the UK.
The findings, presented at the Society for Endocrinology annual conference, provide the only current data on the UK’s iodine status; demonstrating iodine-deficiency in a large sample of the population.
The average urinary iodine level from the population was 80 micrograms per litre, making the group ‘deficient’ by World Health Organisation (WHO) standards.
“Our data suggest the UK is now iodine deficient, warranting a full investigation of the UK iodine status. We need to look into this now to decide whether public health bodies need to step in,” said Dr Mark Vanderpump, a consultant physician at the Royal Free Hampstead NHS, who led the research.
“The World Health Organisation has made iodine-deficiency a global priority and has been campaigning for at-risk countries to add iodine to their salt, a campaign which has been very successful. If it turns out that we do have a problem, this could be the most viable solution,” added Vanderpump.
Iodine is an essential trace element which helps the thyroid gland function properly.
Inadequate dietary iodine intake is the most common cause of preventable mental impairment worldwide. It is defined by the World Health Organisation (WHO) as a population median urinary iodine (UI) excretion of less than 100 micrograms per litre.
According to the WHO, iodine-deficient communities have IQs up to 13.5 points lower than similar but iodine-sufficient communities, even mild deficiency may have an impact on the developing brain of foetuses and young children.
Most people get their iodine from their diet, with many countries now cheaply addressing this issue through a programme of salt iodisation. The UK is yet to join this programme and does not require salt producers to iodise their salt.
“We have performed a systematic assessment of the current UK iodine status in 14–15 years old schoolgirls. Seven hundred and eighty-five participants from nine UK centres provided 737 urine samples,” explained the authors.
Vanderpump and his colleagues reported the median UI value for this sample was 80 micrograms per litre, with 69 per cent of samples found to have values lower than 100 micrograms per litre and 18 per cent of people found to have values lower than 50 micrograms per litre.
They added that further analysis confirmed the findings as independent of confounding factors such as ethnicity, city of origin, and the majority of foods. The researchers did observe a positive association between iodine status and milk intake, however “there was no correlation with other foods,” they said.
“These findings suggest that the UK is now iodine-deficient, consistent with a fall in iodine status recently reported in Australia and USA,” said the authors.
As this was a relatively small audit study that was confined to a single age group and sex, the researchers said that a full-scale investigation into the iodine status of the entire UK population is now warranted.
“We are very concerned about these findings as the consequences of iodine-deficiency are grave: iodine-deficient communities score lower in IQ tests, and even mild iodine-deficiency during pregnancy can cause serious mental impairments in children,” said Dr Vanderpump.
Vanderpump and his co-workers explained that young women of child-bearing age are the most susceptible to the adverse effects of iodine deficiency.
“Even mild perturbations of fetal and maternal thyroid function have an impact upon neurodevelopment so these findings are consequently of huge public health importance,” they said.
They added that the findings “indicate an urgent need for a comprehensive investigation of UK iodine status and evidence based recommendations on the need to implement a policy of iodine prophylaxis.”
Assessment of the UK iodine status: a National Survey. Vanderpump M, Lazarus J, Smyth P et al. (2011) Endocrine Abstracts 25: OC3.8