Effects of fluoride intake on cortical and trabecular bone microstructure at early adulthood using multi-row detector computed tomography (MDCT).

PURPOSE: The aim of this study was to examine the effects of period-specific and cumulative fluoride (F) intake on bone at the levels of cortical and trabecular bone microstructural outcomes at early adulthood using emerging multi-row detector computed tomography (MDCT)-based novel techniques. METHODS: Ultra-high resolution MDCT distal tibia scans were collected at age 19 visits under the Iowa Bone Development Study (IBDS), and cortical and trabecular bone microstructural outcomes were computed at the distal tibia using previously validated methods. CT scans of a tissue characterization phantom were used to calibrate CT numbers (Hounsfield units) into bone mineral density (mg/cc). Period-specific and cumulative F intakes from birth up to the age of 19 years were assessed for IBDS participants through questionnaire, and their relationships with MDCT-derived bone microstructural outcomes were examined using bivariable and multivariable analyses, adjusting for height, weight, maturity offset (years since age of peak height velocity (PHV)), physical activity (questionnaire for adolescents (PAQ-A)), healthy eating index version 2010 (HEI-2010) scores, and calcium and protein intakes. RESULTS: MDCT distal tibia scans were acquired for 324 participants from among the total of 329 participants at age 19 visits. No motion artifacts were observed in any MDCT scans, and all images were successfully processed to measure cortical and trabecular bone microstructural outcomes. At early adulthood, males were observed to have stronger trabecular bone microstructural features, as well as thicker cortical bone (p < 0.01), as compared to age-similar females; however, females were found to have less cortical bone porosity as compared to males. Among participants with available F intake estimates (75 to 91% of the 324 with MDCT scans, depending on the period-specific F intake measure), no statistically significant associations were detected between any period-specific or cumulative F intake and bone microstructural outcomes of the tibia at the p < 0.01 level. Only for females, statistically suggestive associations (p < 0.05) were found between recent F intake (from 14 to 19 years) and trabecular mean plate width and trabecular thickness at the tibia. Those associations became somewhat weaker, but still statistically suggestive, for trabecular thickness in fully adjusted analysis with height, weight, PHV, calcium and protein intake, and HEI-2010 and PAQ-A scores as covariates. CONCLUSION: The findings show that the effects of lifelong or period-specific F intake from combined sources for adolescents typical to the United States Midwest region are not strongly associated with bone microstructural outcomes at age 19 years. These findings are generally consistent with previously reported results of IBDS analyses, which further confirms that effects of lifelong or period-specific F intake on skeletons in early adulthood are absent or weak, even at the levels of cortical and trabecular bone microstructural details.

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 (ß = 21.40, P < .01) and torsion strength (ß = 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.