Fluoride in Drinking Water, Diet, and Urine in Relation to Bone Mineral Density and Fracture Incidence in Postmenopausal Women

Abstract

Background: Although randomized controlled trials (RCTs) have demonstrated that high fluoride increases bone mineral density (BMD) and skeletal fragility, observational studies of low-dose chronic exposure through drinking water ( , the maximum recommended by the World Health Organization) have been inconclusive. Objective: We assessed associations of fluoride in urine, and intake via diet and drinking water, with BMD and fracture incidence in postmenopausal women exposed to drinking water fluoride . Methods: Data were from participants in the Swedish Mammography Cohort–Clinical, a population-based prospective cohort study. At baseline (2004–2009), fluoride exposure was assessed based on urine concentrations ( ) and estimated dietary intake (including drinking water) ( ), and BMD was measured using dual energy X-ray absorptiometry. Incident fractures were ascertained via register-linkage through 2017. Residential history was collected to identify women with long-term consistent drinking water exposures prior to baseline. Results: At baseline, mean urine fluoride was creatinine ( ) and mean dietary intake was ( ), respectively. During follow-up, 850, 529, and 187 cases of any fractures, osteoporotic fractures, and hip fractures, respectively, were ascertained. Baseline BMD was slightly higher among women in the highest vs. lowest tertiles of exposure. Fluoride exposures were positively associated with incident hip fractures, with multivariable-adjusted hazard ratios of 1.50 (95% CI: 1.04, 2.17) and 1.59 (95% CI: 1.10, 2.30), for the highest vs. lowest tertiles of urine fluoride and dietary fluoride, respectively. Associations with other fractures were less pronounced for urine fluoride, and null for dietary fluoride. Restricting the analyses to women with consistent long-term drinking water exposures prior to baseline strengthened associations between fractures and urinary fluoride. Discussion: In this cohort of postmenopausal women, the risk of fractures was increased in association with two separate indicators of fluoride exposure. Our findings are consistent with RCTs and suggest that high consumption of drinking water with a fluoride concentration of may increase both BMD and skeletal fragility in older women. https://doi.org/10.1289/EHP7404

Urinary Fluoride Levels among Canadians with and without Community Water Fluoridation

“…Tap water fluoride predicted UF SG concentration such that every 1 mg/L increase in tap water fluoride is associated with an increase of 0.48 mg/L UF SG after covariate adjustment. The association between tap water fluoride and UF SG was largest for adults and smallest for children, consistent with studies showing that water and other beverages account for approximately 60-78% of dietary fluoride intake among adults, but only 40% of dietary fluoride intake for children 1 to 10 years old [7,40]. Other important sources of fluoride intake in children may include fluoride-containing dental products or foods that are high in fluoride, such as grapes/raisins, shellfish/fish, strained chicken with broth, and processed chicken.…”

“…Older women have higher UF SG than men due to increased fluoride release from bone after menopause [45,46], as well as greater tea consumption [47]. These findings are of public health significance given that chronic exposure to fluoride can change the properties of bone and contribute to skeletal fractures [40], especially post-menopause, with increasing bone loss due to reduced steroid production [48]. A prospective cohort study from Sweden reported a 50% increased risk of hip fractures among postmenopausal women who had higher levels of urinary fluoride [40].…”

“…We also observed sex differences in urinary fluoride levels among older women, perhaps reflecting biologic differences (e.g., role of estrogen in bone remodeling after menopause) or gender-based differences (e.g., higher tea intake in women compared with men). Given growing concerns about adverse health effects of fluoride exposure to the developing fetus [38,59], young children [22,61], and in other vulnerable populations, including those who are iodine deficient [62] or post-menopausal [40], further research is needed to investigate how specific sources of fluoride exposure and timing of exposures may relate to health outcomes across the lifespan.…”

Denser but Not Stronger? Fluoride-Induced Bone Growth and Increased Risk of Hip Fractures

“…3,4 A new study in Environmental Health Perspectives sheds light on this issue, examining the association of fluoride intake with bone mineral density (BMD) and fracture incidence in postmenopausal women. 5 The study used data from the Swedish Mammography Cohort, part of the Swedish Infrastructure for Medical Population-based Life-course and Environmental Research (SIMPLER) project. When the cohort was established in 1987, women completed a questionnaire about lifestyle and dietary habits, with a follow-up survey in 1997.…”

“… 3 , 4 A new study in Environmental Health Perspectives sheds light on this issue, examining the association of fluoride intake with bone mineral density (BMD) and fracture incidence in postmenopausal women. 5 …”