Iodine

Does iodine help brain development in children?

Updated 10 Nov 2026

Short answer

In children with low iodine, supplements give a small gain in some thinking skills.[1][2] A 2026 Cochrane review of 8 trials found a slight increase in cognitive function and likely fewer cases of hypothyroidism.[1] The trials studied children with mild or moderate iodine deficiency.[3][4]

What the studies found

Several studies suggest that moderate to severe iodine deficiency that lasts a long time, mainly in children, lowers IQ by about 12 to 13.5 points.[5]

A 2026 Cochrane review included 8 trials with 2,528 children in 7 countries, done from 1982 to 2009.[1] Its findings:

  • cognitive function: a slight increase (1 trial, 166 children, high certainty)[1]
  • hypothyroidism: likely a large reduction (1 trial, 264 children, moderate certainty)[1]
  • death in infants: likely 68% lower (1 trial, 617 infants, moderate certainty)[1]
  • weight: little or no difference (3 trials, 658 children, low certainty)[1]
  • side effects: no trial reported them[1]

A 2014 review pooled 2 trials in school-age children with mild to moderate deficiency. Iodine improved perceptual reasoning (standardized mean difference 0.55) and a global cognitive score (0.27). The 2 trials differed a lot.[2]

Three trials in detail

In New Zealand, 184 children aged 10 to 13 with mild deficiency took 150 µg of iodine or a placebo every day for 28 weeks. Their median urine iodine rose from 63 to 145 µg/L. Iodine improved 2 of 4 thinking tests, and the overall score was 0.19 standard deviations higher than with placebo.[3]

In Albania, 310 children aged 10 to 12 got one dose of 400 mg of iodine as iodized oil, or a placebo. At the start, 87% had a goiter. After 24 weeks, median urine iodine rose from 43 to 172 µg/L, and iodine improved 4 of 7 tests of information processing, fine motor skills and visual problem solving.[4]

In Indonesia, 617 infants got one dose of 100 mg of iodized oil or a placebo at about 6 weeks of age. The risk of death in the first 2 months was 72% lower with iodine.[6]

Why it may work

  1. The thyroid needs iodine to make T4 and T3.[5]
  2. A fetus and an infant need these hormones for normal growth of the brain.[5]
  3. In the Albanian trial, iodine raised T4 by about 40%, and low T4 almost disappeared.[4]

How studies gave it

  • a daily tablet of 150 µg for 28 weeks, in children aged 10 to 13 with mild deficiency[3]
  • one large dose by mouth, such as iodized oil: 100 mg for infants and 400 to 490 mg for children aged 6 to 17[1][6][4]
  • follow-up of 3 to 22 months after the start[1]

Iodine before birth

Iodine given to the mother in pregnancy is a different question. In women with mild to moderate deficiency, 2 trials found no effect on the child's thinking, language or movement scores.[7] The answer to Do you need an iodine supplement in pregnancy? has the details.[7][8]

Who should be careful

The US upper limit for children is 200 µg a day at 1 to 3 years, 300 µg at 4 to 8 years, 600 µg at 9 to 13 years and 900 µg at 14 to 18 years.[5] The single 400 mg dose was tested in children with moderate deficiency, 87% of whom had a goiter.[4] Doses above the upper limit should only be given under a doctor's care.[5]

What is still unknown

The effects of mild deficiency are harder to measure, and more research is needed.[5] The Cochrane authors asked for trials with higher doses and longer follow-up in areas where iodine deficiency is a problem.[1]

Sources (8)

  1. Iodine supplementation for preventing iodine deficiency disorders in children and adolescents. Velasco I, Rueda-Etxebarria M, Trak-Fellermeier MA, Taylor P, Rabassa Bonet M, Chi Y, et al. Cochrane Database Syst Rev, 2026. PMID 42720098
  2. Therapy of endocrine disease: Impact of iodine supplementation in mild-to-moderate iodine deficiency: systematic review and meta-analysis. Taylor PN, Okosieme OE, Dayan CM, Lazarus JH Eur J Endocrinol, 2014. PMID 24088547
  3. Iodine supplementation improves cognition in mildly iodine-deficient children. Gordon RC, Rose MC, Skeaff SA, Gray AR, Morgan KM, Ruffman T Am J Clin Nutr, 2009. PMID 19726593
  4. Iodine supplementation improves cognition in iodine-deficient schoolchildren in Albania: a randomized, controlled, double-blind study. Zimmermann MB, Connolly K, Bozo M, Bridson J, Rohner F, Grimci L Am J Clin Nutr, 2006. PMID 16400058
  5. Iodine: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  6. Infant survival is improved by oral iodine supplementation. Cobra C, Muhilal, Rusmil K, Rustama D, Djatnika, Suwardi SS, et al. J Nutr, 1997. PMID 9109607
  7. Systematic review and meta-analysis of the effects of iodine supplementation on thyroid function and child neurodevelopment in mildly-to-moderately iodine-deficient pregnant women. Dineva M, Fishpool H, Rayman MP, Mendis J, Bath SC Am J Clin Nutr, 2020. PMID 32320029
  8. Effects of iodine supplementation during pregnancy on pregnant women and their offspring: a systematic review and meta-analysis of trials over the past 3 decades. Nazeri P, Shariat M, Azizi F Eur J Endocrinol, 2021. PMID 33112293

More about iodine

What is iodine?Which foods contain iodine?What is iodine used for?What happens if you do not get enough iodine?Is iodine safe?Do you need an iodine supplement in pregnancy?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.