L-shaped relationship of Vitamin D and blood lead levels among preschool children age 3–6: A cross-sectional study

Background: Childhood lead exposure negatively impacts health, and its link to Vitamin D levels in preschoolers is not well understood.Objective: To investigate the association between Vitamin D and blood lead levels (BLLs) in Chinese preschool children aged 3-6.Methods: A cross-sectional study of 604 children from three Ningbo kindergartens in 2019 measured serum Vitamin D using Chemiluminescence Immunoassay and BLLs via ICP-MS.We used multivariate linear regression, adjusting for factors like age, gender, BMI, hemoglobin, family income, parental occupations, and residential location, and smooth curve fitting to analyze the dose-response relationship.Results: The average age was 5.4 0.8 years, with BLLs at 19.7 12.1 g/L.Each 1 ng/mL increase in Vitamin D correlated with a 0.29 g/L decrease in BLLs (95% CI: -0.43 to -0.16, p < 0.001).The inverse association was significant in males and suburban residents.A threshold effect was identified at 38.679 ng/mL Vitamin D, beyond which BLLs did not decrease further ( = -0.506,95% CI: -0.777 to -0.235, p <0.001).Conclusions: Higher Vitamin D levels are significantly linked to lower BLLs, especially in males and suburban residents, with a threshold at 38.679 ng/mL.Above this, no further BLL reduction is observed, highlighting the importance of optimal Vitamin D levels in mitigating lead exposure.