Comprehensive assessment on iodine nutrition and dietary iodine intake among Shanghai residents

ObjectiveTo assess the changes in iodine nutritional status and dietary iodine intake among Shanghai residents since universal salt iodization 20 years ago.

MethodsAs(Ⅲ)-Ce⁴⁺ Catalytic spectrophotometry was used to determinate the urine iodine level in school-age children, pregnant women, lactating women and adults of Shanghai between 1995 and 2015. B ultrasonic was used to determinate the thyroid volume of school-age children. And then the goiter rate was calculated. Direct titration or arbitration methods were applied to detect the household salt iodine level quantitatively. The survey was conducted by using 3 day 24-hour dietaryx recall and condiment weighing methods to analyze the level of iodine intake and sources for the cases of all iodized salt consumption and all consumption of non-iodized salt.

ResultsThe median urine iodine concentration (UIC) of school age children was 72.3 μg/L in 1995, rose to 214-231 μg/L from 1997-1999, and then remain stable between 100 μg/L and 200 μg/L since 2002. The goiter rate was below 5% among children aged 8-10 from 1995-2015 in Shanghai. The median urine iodine of pregnant women was between 126.5 μg/L and 139.8 μg/L. The median UIC of other populations were all between 100 μg/L and 200 μg/L. For adults, lactating women, infants and young children and women of childbearing age, the median urinary iodine were 138.4, 123.1-131.1, 150.1 and 125.6 μg/L. The qualified iodized salt at household consumption rates were more than 90% from 2001 to 2009, the percentage declined year by year from 2010. In the cases of all consuming iodized salt, the median iodine intake for male aged 7-10, 11-13, 14-18 and over 18 were 200.3, 235.5, 252.7 and 215.4 μg/L, and women aged 7-10, 11-13, 14-18 and over 18 were 193.0, 213.8, 208.3 and 186.1 μg/L. The contribution of iodine from iodized salt were 51.6%-54.1% and 49.1%-53.0% in men and women. Kelp, seaweed and fish and shrimp on the contribution of iodine were 7.6%-16.6% and 4.5%-7.4%.

ConclusionIn the past 20 years, iodine nutritional status of residents in Shanghai has stabilized totally in a appropriate and safe level. However, the iodine nutrition of pregnant women is insufficient. As iodized salt is the major source of dietary iodine in coastal areas, it is still necessary to continue the policy of universal salt iodization in Shanghai to ensure residents' needs for iodine and control the risk of iodine deficiency.