A national survey of iodine nutrition in children aged 3–6 years in China and its relationship with children's physical growth

Iodine, an essential trace element for the human body, plays a pivotal role in sustaining health. Malnutrition has emerged as a pressing public health concern, posing a significant threat to human well‐being. Iodine deficiency poses a substantial threat to the development of children, potentially leading to neurological developmental disorders and mental retardation. Conversely, excessive iodine intake can result in structural and functional abnormalities in the thyroid gland. In this study, we selected children aged 3–6 years through a stratified cluster sampling approach in six regions across China to explore the correlation between iodine nutrition and their physical growth. A total of 5920 preschool children participated in this study, with a median urinary iodine concentration (UIC) of 177.33 [107.06, 269.92] μg/L. Among these children, 250 (4.2%) exhibited stunting, 180 (3.0%) were underweight, 198 (3.3%) experienced wasting, 787 (3.3%) were overweight and 414 (7.0%) were classified as obese. The multivariate linear regression revealed that UIC exhibited a positive correlation with body mass index z‐Score (BMIZ) in overweight children (β = 0.038; 95% CI: 0.001, 0.075). In normally growing children, the associations between UIC and height‐for‐age z‐score, weight‐for‐age z‐score and BMIZ displayed nonlinear patterns. Our findings suggest that iodine nutrition is adequate for Chinese children aged 3–6 years. Furthermore, iodine nutrition is intricately linked to the growth and development of these children. Consequently, it is imperative to implement decisive measures to prevent both iodine deficiency and excess. This study highlights the iodine nutritional status among Chinese children aged 3–6 years, revealing that while levels are generally adequate. Our findings stress the importance of tailored iodine supplementation to support optimal health and development in preschoolers. Key messages This paper is the first large‐scale nationwide epidemiological survey of iodine nutrition in preschool children in China. The median urinary iodine of preschool children in China was 177.33 [107.06, 269.92] μg/L, indicating adequate iodine nutrition. The study suggests that there may be a nonlinear correlation between median urinary iodine and physical growth indicators, such as height‐for‐age z‐score, in preschool children, with gender differences.