Fluoride Decreases Bone Strength

Community water fluoridation has long been touted as a safe and effective means to reduce dental caries in a population, yet data on the long-term safety of low levels of systemic fluoride exposure on the myriad of body systems are either inconclusive or completely lacking. Ingested fluoride is incorporated into the bones, suggesting that exposure over a lifetime, even to the relatively low levels experienced via fluoridated water, may affect the structural or mechanical properties of bone. Chachra et al. (2010) compared bone specimens from residents of fluoridated Toronto to those of non-fluoridated Montreal, with the hypothesis that these populations would reveal patterns consistent with differences in long-term fluoride exposure. The fluoride content of bones from the fluoridated area was significantly higher than those from the non-fluoridated area. Bone from Toronto residents showed greater mean strain at ultimate compressive stress (UCS, an indicator of fracture risk) and greater energy absorbed to failure than bone from Montreal residents. However, the authors failed to control for age, which was greater for those residents in non-fluoridated Montreal. Bones typically weaken with age, and thus the effects of a more elderly population in Montreal may have obscured the full effect of fluoride on the Toronto population. A more relevant finding is that UCS and yield stress declined with increasing fluoride content of bone, indicating that bone strength decreases with increasing bone fluoride level. While similar animal studies have been performed, this is the first human epidemiological study to utilize such an analysis to study fluoride levels and risk of bone fracture, and thus should be seriously considered by public health officials when performing evidence-based risk assessments for fluoride exposures for the whole of the population.

Source:
Chachra D, Limeback H, Willett TL, Grynpas MD. 2010. The long-term effects of
water fluoridation on the human skeleton. Journal of Dental Research 89(11):
1219-1223.