Abstract
BackgroundIodine deficiencies were prevalent in China until the introduction of universal salt iodization (USI) in 1995. In 2012, the standard salt iodine concentration was adjusted to 20-30 mg/kg. The success of USI for the control of iodine deficiency disorders requires monitoring its effect at a population level.MethodsTwo cross sectional surveys of a representative sample of children aged 8–10 years in Zhejiang Province were carried out in 2011 and 2013. Data on participants’ socio-demographic characteristics were collected from the children using a structured questionnaire. Spot urine samples were collected and delivered to local Center for Disease Control and Prevention laboratory for measuring urinary iodine concentration. In 2011, out of 420 selected children aged 8–10 years, 391 were recorded and provided urine samples. In 2013, out of 1560 selected children aged 8–10 years, 1556 were recorded and provided urine samples.ResultsThe median urinary iodine concentration of subjects in the 2013 survey was 174.3 μg/L, significantly lower than that of 2011(p = 0.000). The median urinary iodine concentration of subjects living in urban and rural areas in the 2013 survey was 169.0 μg/L, and 186.1 μg/L respectively, significantly lower than that of 2011 only for subjects living in urban areas (p = 0.000). There were no significant differences for subjects living in rural areas in the survey in 2011 and in 2013 (p = 0.086).ConclusionsAt the time the new local iodization policy put forward, iodine nutrition was generally adequate in both urban and rural areas, suggesting that the new policy for adjusting the standard salt iodine concentration is effective. Our data also indicate that the reason people living in urban areas had a lower urinary iodine concentration than people in rural areas may be due to their preference for using non-iodized salt in the last 2 or 3 years. Maintaining USI at an appropriate level is an important part of preventing iodine deficiency disorders and should always be based on regular monitoring and comparison of urinary iodine concentration by province.
Highlights
Iodine deficiencies were prevalent in China until the introduction of universal salt iodization (USI) in 1995
Iodine deficiency is defined by the World Health Organization (WHO) as a population median urinary iodine concentration that falls below 100 μg/L [8]
Iodine nutritional status surveys are usually done in school age children because they are easy to reach through school based surveys and usually representative of the general population [9,10]
Summary
Iodine deficiencies were prevalent in China until the introduction of universal salt iodization (USI) in 1995. The success of USI for the control of iodine deficiency disorders requires monitoring its effect at a population level. Over the past two decades, salt iodization has been introduced in many countries as a safe, cost-effective and sustainable way to eliminate iodine deficiency disorders (IDD) [1]. Median iodine concentration, measured in a spot urine sample from representative sample is the recommended method to assess the iodine nutritional status of a population [7]. Urinary iodine concentration could not provide direct information on thyroid function, but is a reliable measure of exposure, and a low median value suggests a population is at higher risk of developing thyroid disorders. Iodine nutritional status surveys are usually done in school age children because they are easy to reach through school based surveys and usually representative of the general population [9,10]
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