Fluoride intake and cortical and trabecular bone characteristics in adolescents at age 17: A prospective cohort study.

OBJECTIVE: To investigate the associations between period-specific and cumulative fluoride (F) intakes from birth to age 17 years, and radial and tibial bone measures obtained using peripheral quantitative computed tomography (pQCT).

METHODS: Participants (n = 380) were recruited from hospitals at birth and continued their participation in the ongoing Iowa Fluoride Study/Iowa Bone Development Study until age 17. Fluoride intakes from water, other beverages, selected foods, dietary fluoride supplements and dentifrice were determined every 1.5-6 months using detailed questionnaires. Associations between F intake and bone measures (cortical and trabecular bone mineral content [BMC], density and strength) were determined in bivariate and multivariable analyses adjusted for height, weight, maturity offset, physical activity, and daily calcium and protein intake using robust regression analysis.

RESULTS: Fluoride intake ranged from 0.7 to 0.8 mg F/d for females and from 0.7 to 0.9 mg F/d for males. Spearman correlations between daily F intake and pQCT bone measures were weak. For females, Spearman correlations ranged from r = -.08 to .21, and for males, they ranged from r = -.03 to .30. In sex-specific, height-, weight- and maturity offset- partially adjusted regression analyses, associations between females' fluoride intake and bone characteristics were almost all negative; associations for males were mostly positive. In the fully adjusted models, which also included physical activity, and protein and calcium intakes, no significant associations were detected for females; significant positive associations were detected between F intake from 14 to 17 years and tibial cortical bone content (β = 21.40, P < .01) and torsion strength (β = 175.06, P < .01) for males.

CONCLUSION: In this cohort of 17-year-old adolescents, mostly living in optimally fluoridated areas, lifelong F intake from combined sources was weakly associated with bone pQCT measures.