Fluoride is a mineral, and when present at the right level, it has long been believed to have two beneficial effects: preventing tooth decay and contributing to healthy bones. Adding fluoride to drinking water (fluoridation) to prevent dental caries has often been regarded as one of the top ten public health achievements of the 20th century. In the US, fluoride is added to about 70% public drinking water. However, the benefits of fluoridation have come under recent scrutiny, due to the reliance on evidence from old statistical interpretations, rather than the up-to-date real-world evidence. Reductions in dental caries attributable to fluoridation were initially estimated at approx. 50%-60%. More recent estimates are much lower, 18%--40%, and are thought to probably be lower still, as the widespread use of oral hygiene in general terms has been improving and is now probably the most important factor for reducing dental caries.

Some studies have shown limited differences in tooth decay rates between countries with fluoridated and non-fluoridated water, or between states that fluoridate a high versus low percentage of their water. Higher levels of fluoridation of drinking water have been shown to correlate with an increased incidence of fluorosis, an abnormal condition caused by the excessive intake of fluorides, characterized in children by discolouration and pitting of the teeth. One meta-analysis suggested that, for a fluoride level of 0.7 ppm, the percentage of participants with “fluorosis of aesthetic concern” was approx. 12%. This rose to 40% when looking at fluorosis of any kind.

Numerous studies have shown that excessive fluoride intake in infancy and early childhood can have a wide array of devastating health effects. These outcomes can be irreversible and include structural and functional changes to the central nervous system that can lead to memory, learning and intellectual deficits. Harvard researchers showed that children who live in areas where the level of fluoridation is higher had a “significantly lower IQ than those in low fluoride areas”, further showing a direct link with fluorosis (a consequence of high levels of fluoride in drinking water) and decreased IQ levels, stating that “the results support the possibility of an adverse effect of high fluoride exposure on children’s neurodevelopment”.

There have been literally hundreds of human and animal studies that link excessive fluoride to changes in the brain. These adverse effects include reductions in communication pathways, impaired defence systems and damage to specific regions.

Given the harmful side effects associated with excessive exposure to fluoridated water, it is therefore wise to investigate the level of fluoridation of your own drinking water, particularly in homes with children, whose development may be affected. Those living in areas with fluoridated mains water may wish to consider the use of water filters or bottled water as an alternative source of drinking water, particularly for children.