Children of women with low levels of iodine have lower IQs and reading abilities
Women who are pregnant or planning to have children should ensure they consume the right amount of iodine or risk their child having a low IQ, according to researchers.
A study of more than 1,000 pregnant women found those who consumed lower amounts of iodine, which is absorbed from food and found in milk, dairy products and fish, were more likely to have children with lower IQs and reading abilities.
Iodine is essential for producing hormones made by the thyroid gland, which has a direct effect on the development of the foetal brain.
The study by researchers at Bristol and Surrey universities found two thirds of the 1,040 pregnant women they tested were iodine deficient. These women were more likely to have children with lower IQs, and it was found the lower the iodine the lower the IQ and reading ability.
Professor Margaret Rayman of the University of Surrey, who led the study, said: "Our results clearly show the importance of adequate iodine status during early pregnancy, and emphasise the risk that iodine deficiency can pose to the developing infant, even in a country classified as only mildly iodine deficient."
Researchers have said pregnant women should ensure they get enough iodine by eating dairy products and fish, as well as drinking milk. But they warned against kelp supplements, as they can have ‘excessive levels’ of iodine.
The study, which has been published in The Lancet, used samples from the ‘Children of the 90s’ project, a long term health research project involving 14,000 mothers who enrolled while pregnant during 1991 and 1992. The health and development of their children has been followed ever since.
Dr Sarah Bath, a co-author and registered dietician, said: "Pregnant women and those planning a pregnancy should ensure adequate iodine intake; good dietary sources are milk, dairy products and fish. Women who avoid these foods and are seeking alternative iodine sources can consult the iodine fact sheet that we have developed, which is available on the websites of the University of Surrey and the British Dietetic Association.
"Kelp supplements should be avoided as they may have excessive levels of iodine."
An earlier study based in Tasmania, published in the Journal of Clinical Endocrinology and Metabolism, showed nine year olds who received insufficient iodine in the womb due to a period of deficiency in the population got lower scores on literacy tests.