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Iodine deficiency and cognitive development

Iodine deficiency and cognitive development

Could iodine supplementation be the answer to low intelligence in children?

Iodine is one of several micronutrients in the diet that influence the development of the infant brain. Hence, the effects of both maternal iodine deficiency during pregnancy and iodine deficiency during a child’s early years can be far reaching.

A scientific statement from the European Food Safety Authority claims there is a cause and effect relationship between a woman’s iodine levels during pregnancy and her child’s intelligence.

Severe maternal iodine deficiency during pregnancy has been shown to be associated with lower IQ scores in their children during the early school years, compared with those whose mothers were not iodine deficient while pregnant.

But even mild iodine deficiency in pregnant women can result in adverse educational outcomes: an Australian study found affected children performed badly in spelling, grammar and English literacy. After adjusting for socioeconomic factors, reduction of spelling ability remained significant.

The good news is that supplementing a woman’s iodine intake before and during pregnancy may protect her child from adverse cognitive effects.

A meta-analysis showed that in regions where there is severe iodine deficiency, iodine supplementation may modestly improve perceptual reasoning and global cognitive index in school-aged children. Iodine supplementation for mild to moderate iodine deficiency also improved cognitive performance.

The American Thyroid Association recommends pregnant women have a daily iodine intake of 220–250 μg. The World Health Organization (WHO) recommends 250 μg.

In 2014, the WHO published a guideline on fortification of food-grade salt with iodine for the prevention and control of iodine deficiency disorders. The suggested levels of added iodine depend on the estimated daily salt consumption, including intake of table salt and salt from processed foods. However, this advice should be balanced with the recommendation to reduce salt intake to <5 g/day.

The WHO recommends iodised salt for everyone >1 year of age (infants and young children would receive their iodine via breast milk or from iodine-enriched infant formula milk). Where pregnant women are still not receiving their daily iodine requirement of 250 μg/day, the WHO advocates other interventions such as iodine supplementation.


Further reading

EFSA Journal 2014;12:3517 [10 pp.]. doi:10.2903/j.efsa.2014.3517.

Hynes KL, et al. J Clin Endocrinol Metab 2013;98:1954–62.

Qian M, et al. Asia Pac J Clin Nutr 2005;14:32–42.

Taylor PN, et al. Eur J Endocrinol 2014;170:R1–15.

WHO. Guideline: Fortification of food-grade salt with iodine for the prevention and control of iodine deficiency disorders. Geneva: World Health Organization; 2014.

 

 

Nemencio Nicodemus Jr.

Professor
Department of Biochemistry & Molecular Biology
College of Medicine
University of the Philippines
Manila, Philippines
Clinical Associate Professor
Department of Medicine
Philippine General Hospital
Manila, Philippines
iodine deficiency
Iodine supplementation
pregnancy
cognitive development
Guidelines