Iodine Status of Vulnerable Populations in Henan Province of China 2013-2014 After the Implementation of the New Iodized Salt Standard

The standard of salt iodine content in China has been adjusted several times since implementation of the universal salt iodization (USI) in 1995. The new standard of iodized salt content was adjusted from 35 +/- 15 to 30 +/- 9 mg/kg in Henan province in 2012. We aimed to determine whether the vulnerable populations were iodine sufficient after the adjustment of salt iodine content and to provide a guideline for the adjustment of USI policy in China. Two cross-sectional surveys of iodine status in vulnerable populations, including reproductive-age, pregnant and lactating women, infants < 2 years, and children aged 8-10 years, were conducted in Henan province in 2013 and 2014. In 2013, the median urinary iodine concentration (mUIC) of reproductive-age women was 200.1 mu g/L and that of school children aged 8-10 years was 221.0 mu g/L. These mUICs were considered as more than adequate. The mUICs of reproductive-age women and school children in 2014 showed a significant decline compared to the mUICs in 2013 (P = 0.012 and P = 0.001, respectively). The mUICs of the pregnant women were 204.2 mu g/L in 2013 and 202.5 mu g/L in 2014, which both met the requirement level recommended by WHO. In 2013, the mUIC of lactating women was 169.1 mu g/L and that of infants < 2 years was 203.2 mu g/L, which were significantly lower than that of 2014 (P < 0.001 and P < 0.001, respectively). The lactating women and infants in 2013 and 2014 were both regarded as iodine adequate. Iodine status of the vulnerable populations is still adequate as a whole in Henan province after decreasing the salt iodine content. However, the mUIC of school children aged 8-10 years is slightly above the adequate level. To reduce the risk of iodine excess in the general population and prevent the possibility of iodine deficiency of the vulnerable population, it is necessary to explore the appropriate level of iodized salt content.