BACKGROUND: Relationships between fluoride intake and bone health continue to be of interest, as previous studies show conflicting results.
OBJECTIVES: The purpose is to report associations of fluoride intake with bone measures at age 11.
METHODS: Subjects have been participating in the ongoing Iowa Fluoride Study/Iowa Bone Development Study. Mothers were recruited postpartum during 1992-95 from eight Iowa hospitals, and detailed fluoride questionnaires were sent every 1.5-6 months. From these, combined fluoride intakes from water sources (home, childcare, filtered, bottled), other beverages, selected foods, dietary fluoride supplements and dentifrice were estimated at individual points and cumulatively [with area under the curve (AUC)]. Subjects underwent dual-energy X-ray absorptiometry (DXA) scans of proximal femur (hip), lumbar spine and whole body (Hologic QDR 4500A). DXA results (bone mineral content – BMC; bone mineral density – BMD) were related to fluoride intake as revealed by bivariate and multivariable analyses.
RESULTS: The mean fluoride intake estimated by AUC was 0.68 mg (SD = 0.27) per day from birth to 11 years. Associations (Spearman) between daily fluoride intake (mg F/day) and DXA bone measures were weak (r = -0.01 to 0.24 for girls and 0.04 to 0.24 for boys). In gender-stratified, and body size- and Tanner stage-adjusted linear regression analyses, associations between girls’ bone outcomes and fluoride intake for girls were almost all negative; associations for boys were all positive and none was statistically significant when using an alpha = 0.01 criterion.
CONCLUSIONS: Longitudinal fluoride intake at levels of intake typical in the United States is only weakly associated with BMC or BMD in boys and girls at age 11. Additional research is warranted to better understand possible gender- and age-specific effects of fluoride intake on bone development.