LONDON: Iodine deficiency during pregnancy - rampant among Indian women, adversely affects the child's mental development.
A large scale UK study published in the medical journal The Lancet on Thursday has shown that iodine - which is consumed mainly via dairy products and seafood - is essential for producing the hormones made by the thyroid gland, which have a direct effect on fetal brain development.
A recent Indian health ministry survey conducted in 324 districts across the country found that 263 districts are still endemic with Iodine Deficiency Disorders (IDD) like brain damage, miscarriages, dwarfism and mental retardation.
A group of researchers from Surrey and Bristol universities, followed 1000 pregnant UK women and measured the iodine concentration in urine samples taken in the first trimester.
Following World Health Organisation (WHO) guidelines on recommended concentrations of iodine during pregnancy, they classified women who had an iodine-to-creatinine ratio of less than 150 as being iodine deficient, and those with a ratio of 150 or more as iodine sufficient.
Over two thirds (67%) of the women fell into the category of less than 150.
Mental development of the women's children was then assessed by measuring child IQ at age 8 and reading ability at age 9.
Adjusting the results for external factors such as parental education and breast-feeding, the researchers found that children of women in the iodine-deficient group were significantly more likely to have low scores of verbal IQ, reading accuracy, and reading comprehension.
Moreover, the lower the mother's concentration of iodine, the lower were the average scores for IQ and reading ability in the children.
According to lead author Professor Margaret Rayman of the University of Surrey "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."
The research raises concerns that the iodine status of pregnant women is a public health issue that needs to be addressed.
Dr Sarah Bath, co-author added "Pregnant women and those planning a pregnancy should ensure adequate iodine intake; good dietary sources are milk, dairy products and fish."
Previous results have indicated that a mother's consumption of seafood during pregnancy was associated with her child's mental development, with lower seafood consumption associated with poorer scores in reading and IQ tests.
At the time, researchers speculated that this might be due to higher levels of omega-3 fatty acids in seafood, but the current study - which also adjusted for mothers' intake of omega-3 fatty acids as a possible confounder on the effects on cognitive development - suggests that these effects could have had more to do with iodine concentrations than previously realised.
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