CANTERBURY, UK. Community water fluoridation goes back to the 1950s. The merits of this have been debated ever since. The level is typically 0.7 to 1.0 mg fluoride per liter of water. To this is added that absorbed from toothpaste unless one uses the fluoride free product. Studies have suggested that fluoride is associated with hypothyroidism which is biologically plausible since it is a member of the halogen family which includes bromine and iodine, and it binds to iodine receptors. In fact, historically fluoride was used as a treatment to reduce thyroid activity. An interesting study in the UK further addresses this concern. Two large residential areas were identified, one with and one without fluoridation. In each area general medical practitioners were recruited and the association between the incidences of hypothyroidism determined. In all, almost 800 practices were involved. Practices in the fluoridated areas were twice as likely to report high hypothyroidism prevalence as those in the non-fluoridated area. These results highlight a significant public health issue since hypothyroidism is far from a trivial disorder.

Peckham S, Lowery D, Spencer S. Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water. J Epidemiol Community Health 2015 February 24