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Fluoride does not affect intelligence

1 March 2018

Fluoride does not affect intelligence

It is a well-known fact that fluoride is beneficial to oral health. Fluoride is a naturally occurring mineral found in water and some foods. Naturally occurring fluoride in water varies across the country. In the early 20th century, it was discovered that people had less tooth decay in areas with higher fluoride levels in their drinking water. This observation ultimately led to the introduction of water fluoridation schemes to reduce levels of tooth decay.  When children eat or drink fluoride in small doses, it enters the bloodstream and becomes part of their developing permanent teeth. Swallowed fluorides also become part of the saliva and strengthen teeth from the outside, thus inhibiting the ability of acids to damage tooth enamel. In some areas, the natural level of fluoride is close to, or even slightly greater than, the level that water fluoridation schemes aim to achieve.

Water companies adjust the level of fluoride to 1mg of fluoride per litre of water, the level found to reduce tooth decay. This is carefully controlled and monitored. Water fluoridation has the support of the World Health Organisation, professional health bodies in the UK like the British Medical Association and British Dental Association, and the US Centres for Disease Control.

Areas in the Midlands such as Birmingham have had fluoridated water since the early 1960s and have had much lower levels of tooth decay than comparable areas in England where the water does not have added or naturally occurring fluoride. Around 5.8 million people in England, across 27 councils, receive fluoridated water.

Among children aged one to four in the UK, child hospital admissions due to tooth decay are halved in fluoridated areas compared to non-fluoridated. At the levels permitted in these areas, there is no evidence of it causing harm.

There have been several reports over the years claiming that fluoride can damage the brain. In July 2012, a team of Harvard researchers published a ‘meta-analysis’ of 27 studies that investigated the relationship between elevated fluoride and reduced IQ. The team concluded that the effects of fluoride on the developing brain of children should be a ‘high research priority’ in countries such as the U.S. where no previous investigation into this issue had been done. Two researchers at Uppsala University showed in a working paper from IFAU that a higher level of fluoride in the drinking water does not lead to lower intelligence. The researchers concluded that there was no correlation between the fluoride levels and IQ.

“Our study is the largest of its kind and we do not find that the fluoride levels in Sweden are harmful to the intelligence” says Mattias Öhman, who is one of two researchers behind the study. The levels studied here exceeded those in Swedish municipal drinking water.

The only potential negative impact of too much fluoride is dental fluorosis, where white patches or lines can form on the teeth, although this condition is common in both fluoridated and non-fluoridated areas.

Although tooth decay is the most widespread chronic disease in cities and is also the most common childhood disease, there are those who are opposed to the fluoridation of water for ethical reasons, such as the violation of an individual’s consent to medication, the potential threat to animals and rejection of the “one fits all” model.



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Top Ten Reasons to Oppose Water Fluoridation. (2018). IAOMT. Retrieved 27 February 2018, from

White, S. (2018). Water fluoridation- what it is and how it helps dental health - Public health Retrieved 27 February 2018, from

Wylie, I. (2018). Something in the water: is fluoride actually good for cities?the Guardian. Retrieved 27 February 2018, from

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