Iodine supplementation into drinking water improved intelligence of preschool-children aged 25-59 months in Ngargoyoso sub-district, Central Java, Indonesia: A randomized control trial

To date there is no iodine supplementation trial in relation to intelligence of the preschool children aged 25-59 months reported. Therefore, the aim of the study was to test hypothesis whether iodine supplementation presented in “kendi” (water-pitcher) can increase urinary iodine excretion and the intelligence quotients of preschool children aged 25-59 months. A randomized, placebo, controlled trial was conducted in Ngargoyoso sub-district, Central Java, Indonesia. Sixty-seven preschool children aged 25-59 months with urinary iodine excretion <100µg/L were allocated randomly into two groups. The treatment group received 100µg iodine/day and the control group received placebo for twelve weeks. Urinary iodine excretion was measured by using method A (Sandell-Kolthoff reaction) at an accredited laboratory for iodine measurement. Intelligence scores were measured by using Stanford-Binet Scale. Basal and post-treatment data on urinary iodine excretion and intelligence scores were then compared and analyzed using Student’s t test. Statistically, urinary iodine excretion significantly increased from 62.45 (±26.21) µg/L to 244.55 (±120.19) µg/L and from 71.15 (±22.32) µg/L to 120.00 (±79.77) µg/L in the treatment and placebo groups, respectively. Comparison between groups revealed significant difference (p<0.001). Intelligence scores in the treatment group increased significantly from 101.48 (±11.03) points to 110.27 (±9.40) points, while in the control group there was a decrease from 105.18 (±9.62) points to 103.06 (±9.99) points. Iodine supplementation (100µg/day) within 12 weeks increases intelligence scores by 8.8 points. Keywords: iodine supplementation, preschool-children, urinary-iodine- excretion, intelligence scores, kendi