Iodized Salt Coverage and Influencing Factors in Chinese Out-of-Home Dining Venues: A Large Cross-Sectional Study from 31 Provinces of China

<b>Background/Objectives:</b> With the rising trend of out-of-home dining in China, the use of iodized salt (IS) in eating-out venues plays a key role in preventing iodine deficiency disorders (IDDs). However, the coverage rate of iodized salt (CRIS) and the utilization rate of adequately iodized salt (URAIS) in these venues in China remain underexplored, potentially undermining IDD prevention strategies. This study aims to assess the CRIS and URAIS in such venues across China and identify the factors influencing their prevalence. <b>Methods</b>: From 2021 to 2024, a nationwide cross-sectional study was conducted in China, involving 19,346 venues. A 50 g sample of cooking salt was collected from each venue, and the iodine content was measured. The CRIS and URAIS were calculated, and associations with various factors were assessed using Chi-square tests, the Cochran-Armitage trend test, and multivariate logistic regression. <b>Results</b>: Of the 19,346 samples, 18,519 tested positive for IS, and 17,588 contained adequately iodized salt (AIS), resulting in a CRIS of 95.7% and a URAIS of 90.9%. Significant regional differences were found, with coastal areas showing a lower CRIS and URAIS than inland areas (87.0% vs. 97.8%; 81.0% vs. 93.2%) and urbanized areas having lower rates compared to less urbanized areas (94.1% vs. 97.3%; 88.9% vs. 92.9%). Higher per capita income was associated with a lower CRIS and URAIS (Z = -19.72, <i>p</i> < 0.0001; Z = -13.85, <i>p</i> < 0.0001). Lower per capita income (OR = 3.24, OR = 1.36, <i>p</i> < 0.0001), inland areas (OR = 4.14, OR = 2.68, <i>p</i> < 0.0001), and mountainous areas (OR = 2.48, OR = 1.27, <i>p</i> < 0.0001) were associated with a higher likelihood of IS and AIS use. <b>Conclusions</b>: While the CRIS and URAIS in dining venues meet national standards, regional disparities persist, particularly in coastal, plain, and economically advanced areas. Strengthening regulatory oversight and public education on iodized salt's health benefits is essential.