Iodine supplementation improves cognition in iodine-deficient schoolchildren in Albania: a randomized, controlled, double-blind study.
BACKGROUND
Iodine is required for the production of thyroid hormones, which are necessary for normal brain development and cognition. Although several randomized trials examined the effect of iodine supplementation on cognitive performance in schoolchildren, the results were equivocal.


OBJECTIVE
We aimed to ascertain whether providing iodized oil to iodine-deficient children would affect their cognitive and motor performance.


METHODS
In a double-blind intervention trial, 10-12-y-old children (n = 310) in primary schools in rural southeastern Albania were randomly assigned to receive 400 mg I (as oral iodized oil) or placebo. We measured urinary iodine (UI), thyroid-stimulating hormone (TSH), and total thyroxine (TT4) concentrations and thyroid gland volume (by ultrasound). The children were given a battery of 7 cognitive and motor tests, which included measures of information processing, working memory, visual problem solving, visual search, and fine motor skills. Thyroid ultrasound and the biochemical and psychological tests were repeated after 24 wk.


RESULTS
At baseline, the children's median UI concentration was 43 microg/L; 87% were goitrous, and nearly one-third had low concentrations of circulating TT4. Treatment with iodine markedly improved iodine and thyroid status: at 24 wk, median UI in the treated group was 172 microg/L, mean TT4 was approximately 40% higher, and the prevalence of hypothyroxinemia was < 1%. In the placebo group after the intervention, these variables did not differ significantly from baseline. Compared with placebo, iodine treatment significantly improved performance on 4 of 7 tests: rapid target marking, symbol search, rapid object naming, and Raven's Coloured Progressive Matrices (P < 0.0001).


CONCLUSIONS
Information processing, fine motor skills, and visual problem solving are improved by iodine repletion in moderately iodine-deficient schoolchildren.
Zimmermann
Michael B
MB
Laboratory for Human Nutrition, Swiss Federal Institute of Technology Zürich, Zürich, Switzerland. michael.zimmermann@ilw.agrl.ethz.ch
Connolly
Kevin
K
Bozo
Maksim
M
Bridson
John
J
Rohner
Fabian
F
Grimci
Lindita
L
D000415:Albania / Q000453:epidemiology; D002648:Child; D003071:Cognition / Q000187:drug effects*; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006042:Goiter / Q000097:blood / Q000188:drug therapy* / Q000453:epidemiology; D006801:Humans; D007455:Iodine / Q000008:administration & dosage / Q000172:deficiency* / Q000652:urine; D007459:Iodized Oil / Q000008:administration & dosage*; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D015995:Prevalence; D011594:Psychometrics; D013961:Thyroid Gland / Q000000981:diagnostic imaging*; D013963:Thyroid Hormones / Q000097:blood*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D016896:Treatment Outcome; D014463:Ultrasonography
D013963:Thyroid Hormones; D007459:Iodized Oil; D013972:Thyrotropin; D007455:Iodine; D013974:Thyroxine