Dairy products are a significant source of iodine, and their contribution to iodine intake must be evaluated regularly. However, there is a lack of data on iodine intake from dairy products in China. Through a cross-sectional study, we determined the iodine content of dairy products in the Chinese diet and estimated iodine intake among Chinese children. Intake records for 30 consecutive days were used to investigate the consumption of dairy products by 2009 children from Yunnan and Liaoning Provinces. The iodine contents of 266 dairy products with high intake frequency were determined using inductively coupled plasma–mass spectrometry (ICP-MS). We then calculated the iodine intake and contribution of dairy products and explored the related factors of dairy iodine intake through a generalized linear mixed model. Ultra-high-temperature (UHT) sterilized milk accounted for 78.7% of the total dairy products, with an iodine content of 23.0 μg/100 g. The dairy product intake rate of children in China was 83.6%, with an average daily intake of 143.1 g. The median iodine intake from milk and dairy was 26.8 μg/d, 41.5% of the estimated average recommendation (EAR) for younger children and 31.8% of the EAR for older children. The daily milk iodine intake of children in Yunnan Province was 9.448 μg/day lower than that of children in Liaoning Province (p < 0.001), and the daily iodine intake of children in rural areas was 17.958 μg/day lower than that of children in urban areas (p < 0.001). Chinese dairy products were rich in iodine, and the content of iodine was intermediate to that reported in Europe and the USA. However, children’s daily intake of milk iodine was lower than that of children in other developed countries due to the lower daily intake of dairy products, especially those in rural areas.

Background: The residents of both the agricultural and pastoral areas of Tibet share the same iodine deficiency and iodine nutrition, but the rate of thyroid goiter was significantly higher in the agricultural areas than in the pastoral areas. This project sought to determine why the populations in the iodine-deficient pastoral areas show a lower rate of thyroid goiter. Methods: Food frequency questionnaires (FFQs) and 24 h history recalls were adopted to investigate the dietary patterns of the residents of the agricultural and pastoral areas. Meat and milk samples were collected to measure their inorganic iodine, total iodine and thyroid hormone contents using ICP-MS, As^III-Ce⁴⁺ catalytic spectrophotometry and the Siemens’ chemiluminescence method, respectively. The intake of protein, and the microelements, selenium and iron, was calculated according to their content in the food. Results: The per capita daily intake of meat, dairy, and cereal in the pastoral areas was 116.7, 216.7, and 433.3 g, respectively, which are significantly higher than those in the agricultural areas (50.0, 72.2, and 375.0 g, respectively) (p < 0.05). The content of thyroid hormone in dried beef and milk in the pastoral areas was 62.6 and 13.5 μg/kg, respectively, which was significantly higher than those in the agricultural areas (25.1 and 4.1 μg/kg, respectively) (p < 0.05). The daily intake of thyroid hormone, protein and microelements, selenium and iron from foods by the residents of the pastoral areas were 10.5 μg, 99.6 g, 30.0 μg and 15.8 mg respectively, which was significantly higher than those in the agricultural areas (1.79 μg, 56.5 g, 23.8 μg and 13.2 mg, respectively) (p < 0.05). Conclusions: The significantly high intake of the food-borne thyroid hormone by the residents of the pastoral area could be the main reason the residents in the pastoral areas show a lower rate of thyroid goiter than those in the agricultural area. Moreover, the relatively high intake of protein and trace elements, selenium and iron by residents in the pastoral area could be another important factor for reducing the goiter rates.

What is already known about this topic? The National Iodine Deficiency Disease Surveillance system is exclusively focused on monitoring cooking salt used within households. Currently, there is a lack of nationally representative data on the use of iodized salt in dining establishments. What is added by this report? This study evaluated 7,889 salt samples obtained from dining establishments located in 13 provincial-level administrative divisions across China. The findings indicated that coverage rate of iodized salt (CRIS) and the consumption rate of adequately iodized salt (CRAIS) were found to be 95.2% and 90.2%, respectively. Further, 880 samples were classified as iodized salt and 804 as adequately iodized salt. In coastal areas, the CRIS and CRAIS showed a significant decrease to 77.1% and 70.5%, respectively, when compared to the inland regions (P<0.01). What are the implications for public health practices? The data compiled could potentially fill the void in the national data concerning the use of iodized salt in dining establishments throughout China. It is of the utmost importance to increase the awareness of restaurant operators, particularly those located in coastal areas, about the benefits of iodine supplementation. Moreover, they should be encouraged to use adequately iodized salt.

Dairy products, a good source of iodine, have been shown to influence the iodine level of pregnant women. This study aimed to investigate the dairy iodine content, the dairy products, and dairy iodine intake of Chinese pregnant women, and related factors. A cross-sectional study included 1,013 pregnant women in Liaoning and Yunnan provinces, China. The eligible participants completed the intake records for 30 consecutive days to collect characteristics and dairy consumption. Dairy iodine intake was calculated, and the related factors were explored using the Mann-Whitney, Kruskal-Wallis H, and Jonckheere-Terpstra trend tests. An analysis compared dairy iodine intake in pregnant women to the dietary reference intakes of iodine. The iodine content of pasteurized milk (26.3 μg/100 g vs. 14.7 μg/100 g, Z = -2.335) and yogurt (21.5 μg/100 g vs. 12.6 μg/100 g, Z = -2.668) was significantly higher in Liaoning than in Yunnan province. The average dairy intake of pregnant women was 147.4 g/d, and dairy iodine intake was 31.9 μg/d. There were significant differences in dairy iodine intake by age group, province, urban or rural area, ethnicity, and education levels. The median dairy iodine intake in this study only met 12.9%-23.4% of the estimated average requirement and 9.0%-16.3% of the recommended nutrient intake (RNI) of local pregnant women in the 2 provinces, respectively. Consuming 500 g of dairy products provides approximately 92.5-121.0 μg of iodine. Combined with typical iodine intake from iodized salt and other foods, this would help pregnant women meet 105%-117% of the RNI for iodine. In conclusion, pregnant women with low levels of education, in rural areas, or from the Lahu ethnic group have a lower intake of dairy products and dairy iodine. Approximately 500 g of dairy products plus 5 g of iodized salt and other foods per day will ensure adequate iodine intake for pregnant women in areas with low water iodine.