How to Decide the Iodine Content in Salt for a Country—China as an Example

Globally, many countries have implemented universal salt iodization to prevent and control iodine deficiency disorders. Therefore, it is important to determine the optimal iodine content in salt and to adjust it in a timely manner. This article aims to establish a process for selecting, deciding, and evaluating the iodine content in salt for China and, if possible, providing references for other countries. Information on salt intake, water iodine, and iodine stability in salt was collected. A field investigation was carried out in different populations in four provinces. Iodine intake was calculated and the appropriate iodine content for salt preliminarily obtained, then verified for suitability with 2020 China National Iodine Deficiency Disorders Surveillance data. In total, 2837 children, 1660 adults, and 2145 pregnant women were enrolled, and their iodine intake from food was 3.7–96.1, 60.0–156.0 and 65.0–112.0 µg/d, respectively. After calculation, when the iodine content in salt was 20, 25 and 30 mg/kg, for children and adults, the total iodine intake ranged from 173.4 to 253.5 µg/d and 230.3 to 379.8 µg/d, respectively. When the iodine content in salt was 30 and 35 mg/kg, for pregnant women, the total iodine intake was 296.8–408.9 µg/d, which was between the recommended nutrient intake and tolerable upper intake level. Therefore, in China, the iodine content in salt in the general population can be preset as 20, 25 and 30 mg/kg, and that in pregnant women 30 and 35 mg/kg, with a variation of ±5 mg/kg based on the automatic spraying technique used in the salt processing plant. Iodine nutritional status was then evaluated according to the preset iodine content in the salt, and it reached the appropriate level for the different populations. The iodine content in salt in China was decided and verified, and the procedure of selecting the iodine content in salt was established for the reference of different countries.