Associations of personal solar UV exposure with gut microbiota diversity and BMI among preschool children in China

OBJECTIVES: Solar ultraviolet radiation (UVR) exposure has been recognized as a modulator of metabolic health, ranging from indirect effects on physical activity and lifestyle to direct biological impact on energy metabolism. This study examines the relationship between personal UVR exposure and BMI in preschool children in China, with a focus on the mediating role of gut microbiota-mediated mechanisms. METHODS: A cross-sectional study was conducted on 405 preschool children from three cities in China. Personal UVR exposure was assessed using the modelling framework, and age- and sex-specific BMI z-scores were calculated based on growth reference values. Fecal samples were analyzed using 16S rRNA sequencing to characterize gut microbiota composition. Structural equation modeling (SEM) examined the relationships between personal UVR exposure, gut microbiota diversity, and BMI z-score. A mediation analysis was performed to identify key gut microbiota genera contributing to these associations. RESULTS: Higher personal UVR exposure was significantly associated with lower BMI z-score. SEM results indicated that UVR exposure was positively related to microbial diversity and inversely associated with BMI z-score. Mediation analysis further confirmed that Lactobacillus exhibited the most substantial mediating effect, followed by Lachnospira, Coprococcus, and Bifidobacterium. CONCLUSIONS: Personal UVR exposure may contribute to BMI regulation in preschool children, which is partially mediated by changes in the abundance of specific gut microbiota genera, highlighting the UVR exposure's potential as a natural and non-invasive intervention for children with overweight/obesity. Future studies should explore the long-term effects and underlying molecular mechanisms to inform public health strategies.