Objectives
To investigate efficacy of iodine supplementation in 18-45-yr iodine deficient women in improving iodine status, thyroid function, and body composition.
Methods
6-month randomized controlled trial. Non-pregnant (euthyroid, normal thyroid stimulating hormone (TSH), mean=1.57 µU/mL) women were randomized into two groups: 12.5mg iodine (IG, n=65) or placebo (PG, n=38). Assessments: iodine status (24-hr urine iodine (UI), %-iodine saturation (%IS), sodium-iodide-symporter-ratio (NIS)), body composition analysis using Dual Energy X-ray Absorptiometry, resting metabolic rate (RMR), thyroid function (TSH, free thyroxine (T4), free tri-iodithyronine (T3), thyroglobulin and thyroid peroxidase antibodies, 3-day diet records, health history and physical activity questionnaires.
Results
>90% reported reduced salt intake in diets, no knowledge of dietary sources of iodine, and did not know difference between iodized vs. regular table salt. Median consumption of dietary iodine was <100 µg/day, significantly <150 µg/day RDA for iodine, <250 µg/day (pregnancy and lactation). Mean baseline data (N=108) showed UI of 35.52mg/24hr vs >44 mg/24hr, %IS 70.93% vs >90%, and NIS-ratio 27.86 vs 28-74, between study population and expected mean, respectively, indicating iodine deficiency. Of those completing study (n=64; IG, n=32, PG, n=32), UI increased from 34.9-38.1 mg/24hr, %IS from 69.8-76.3%, and RMR from 1586-1628 Kcals. Between groups UI increased from 35.8-39.6 mg/24hr (IG) vs 34.0-36.6 mg/24hr (PG), %IS from 71.6-79.3% (IG) vs 67.9-73.2 (PG), and RMR from 1600-1650 Kcals (IG) vs 1572-1607 Kcals (PG).
Conclusions
Iodine supplementation may improve overall iodine nutrition status in reproductive-age women with decreased dietary iodine intakes that are especially vulnerable to the detrimental maternal and fetal effects of iodine deficiency.
