Strontium and Barium in Deciduous Teeth and Infant Feeding Methods: A Birth Cohort Adjunct Study to the Japan Environment and Children's Study.

Background: Deciduous teeth are a unique medium that record exposure to various elements over time, as they are formed during fetal and infantile periods. We aimed to evaluate the association between infant feeding methods and changes in the distribution of Barium (Ba) and Strontium (Sr) in deciduous teeth of children.

Methods: The current analysis included 216 children around 6-7 years of age whose deciduous central incisor teeth were provided between March 2018 and February 2020, as an adjunct study of the Japan Environment and Children's study. Ba, Sr, and Calcium (Ca) levels in the deciduous teeth of these children were measured using laser ablation-inductively coupled plasma-mass spectrometry. We estimated the association between feeding methods or season of birth and the Ba to Ca (Ba:Ca) and Sr to Ca (Sr:Ca) ratios using multivariable linear mixed effects models.

Results: The Ba:Ca and Sr:Ca ratios were higher in the formula feeding group than in the breastfeeding group during the postnatal period [Ba:Ca: β=0.242 (95% CI: 0.149-0.335), Sr:Ca: β=0.223 (95% CI: 0.160-0.287) for formula group] and prenatal period [Ba:Ca: β=0.145 (95% CI: 0.062-0.227), Sr:Ca: β=0.152 (95% CI: 0.093-0.210) for formula group]. Furthermore, the Sr:Ca ratio tended to be higher for summer-born children than for winter-born ones.

Conclusion: The Ba:Ca and Sr:Ca ratios in deciduous teeth can serve as useful biomarkers for estimating feeding methods. Deciduous central incisors may serve as useful indicators of longitudinal elemental exposure and nutritional status from the prenatal to postnatal periods.