Evaluation of iodine nutritional status in Tehran, Iran: iodine deficiency within iodine sufficiency

Production of iodized salt in Iran for household consumption began in 1990. Previous studies have reported sustainable elimination of iodine deficiency disorders in Iran. The aim of this study was to evaluate the iodine nutritional status in Tehran in 2009.

In this cross-sectional study, 383 Tehranian households were enrolled through randomized cluster sampling and a total of 639 adult subjects (242 men and 397 women), aged 19 and over, participated. A 24-hour urine sample was collected for measurement of urinary iodine, sodium, and creatinine concentrations using the digestion method, flame photometry, and autoanalyzer assay, respectively. Salt intake was estimated and iodine content of household salt was measured by titration.

Median (interquartile range) iodine content of household salt and urinary iodine concentration (UIC) in Tehran were 21.2 (3.2-31.7) parts per million and 70.0 (34.0-131.2) μg/L, respectively. There was no statistically significant difference in 24-hour UICs between men and women. Median (interquartile range) daily salt intake was 7.6 (5.5-9.8) g, which was not different in the two genders. According to the WHO/ICCIDD/UNICEF classification, 11.2%, 25.9%, 26.7%, 25.1%, 8.0%, and 3.2% of participants had UIC <20, 20-49, 50-99, 100-199, 200-299, and >300 μg/L, respectively.

Mild iodine deficiency has recurred in Tehranians. The results emphasize the need for continuous monitoring in all regions, even in a country with iodine sufficiency.