Dietary Iodine Intake and Sources among Residents in Zhejiang Province 10 Years after Reducing Iodine Concentration in Iodized Salt

Abstract

We aimed to assess dietary iodine intake and sources in Zhejiang Province a decade after a reduction in iodine concentration in iodized salt. Three-day 24 h dietary recall and household weighing were used, complemented by “Chinese Food Composition” data. Household water and salt samples were collected from 5890 residents and analyzed. Differences in iodized salt consumption rates were observed across the following regions: inland (84.20%), subcoastal (67.80%), and coastal (37.00%) areas. The median (P25, P75) iodine concentration in water and diet were 2.2 (0.9, 4.0) μg/L and 142.05 (58.94, 237.11) μg/d, respectively, with significant regional differences in dietary concentration (inland [185.61 μg/d], subcoastal [153.42 μg/d], and coastal [75.66 μg/d]). Males (149.99 μg/d) and iodized salt consumers (191.98 μg/d) had a significantly higher dietary iodine intake than their counterparts. Regions were ranked as follows based on the proportions of individuals meeting the recommended dietary iodine intake: inland (69.40%), subcoastal (56.50%), and coastal (34.10%) areas. Dietary sources included salt (48.54%), other foods (32.06%), drinking water (8.84%), laver (4.82%), kelp (3.02%), and other seafood (2.32%). The qualified iodized salt consumption rate was significantly lower than the national standard. Zhejiang Province should continue implementing measures to control iodine deficiency through salt iodization, education efforts, and increasing the qualified iodized salt consumption rate.