It’s added to water drunk by 6 million Brits and could soon be rolled out to even more of us. But there are growing fears that fluoride could be linked to a devastating disease

Every time they take a sip of tap water, some 6 million people in England also consume something a little extra, an added ingredient most will be completely unaware of.

Called fluoride, it’s colourless, odourless and tasteless and has been added to the domestic water supply in some parts of the country for the past 60 years or so to help prevent tooth decay.

Areas with fluoridated water include Birmingham (the first to introduce it, back in 1964), Cumbria, Cheshire, Coventry, Doncaster, Tyneside and parts of Oxford.

Fluoride is a mineral found also naturally in foodstuffs such as tea, coffee, shellfish, potatoes and porridge and it helps to strengthen enamel – the hard outer coating on our teeth – making it more resistant to decay triggered by sugary diets.

Some dental health experts describe its addition to drinking water supplies as one of the greatest public health initiatives the UK has ever seen.

And now the Labour government is expected to follow-through on plans drawn up by its Conservative predecessors – in the Health and Care Act 2022 – to expand water fluoridation to millions more people in an attempt to improve the nation’s dental health.

For years, it has been left to local authorities to decide whether or not to supplement local water supplies with the mineral – based on levels of tooth decay and the cost of implementing the schemes.

The Health and Care Act 2022 passes this responsibility to the Department of Health and Social Care, enabling it to oversee the expansion of the fluoridation programme.

But is this kind of ‘mass medication’ really necessary and, more to the point, is adding fluoride to everybody’s drinking water even safe?

The issue hit the headlines after Robert F Kennedy Jr – US President-elect Donald Trump’s choice as health secretary – said recently on X (formerly Twitter) that when Trump takes office in January, he will advise all US water companies to immediately remove fluoride from their supplies.

Around two-thirds of the US population drinks water with added fluoride to combat dental decay and numerous studies show it works – dental health improves as a result.

Studies show that on average, adding fluoride to drinking water reduces the number of decayed teeth in young children by around two teeth per child.

But Kennedy, a known vaccine sceptic, wrote online last month: ‘Fluoride is … associated with arthritis, bone fractures, bone cancer, IQ loss, neurodevelopmental disorders and thyroid disease.’

When sugar from food or drink enters the mouth, the bacteria lurking on our gums converts it into acid which breaks down the enamel on our teeth and causes decay – a process called demineralisation.

Fluoride bonds to the enamel and reverses this decline, leading to remineralisation, which reinforces the teeth against acid attacks.

This is particularly important in young children, as their teeth tend to have thinner enamel, putting them at greater risk of cavities.

NHS England figures – released in September – showed tooth decay is the leading cause of hospital admissions among the under-tens, with more than 19,000 needing rotting teeth extracted in 2023/24, at a cost to the NHS of some £50m.

However, Kennedy’s social media post was prompted by a recent ruling by a district judge in California, who ordered the US Environmental Protection Agency – which oversees water safety – to impose tough regulations on fluoride in drinking water because high levels could pose a risk to the intellectual development of children.

District judge Edward Chen was ruling on a case brought by anti-fluoride groups arguing the policy is harmful to health.

Numerous studies down the years have suggested excess fluoride intake can harm children’s IQ – possibly by damaging areas of the brain involved in memory and learning through oxidative stress, where harmful molecules called free radicals destroy brain cells.

One of the most recent, published in Environmental Research in 2023, found that children’s IQ dropped an average of 3 points (most children under ten score between 30 and 50 on IQ tests) when fluoride in drinking water measured around one milligram per litre The World Health Organisation recommends a maximum level of 1.5 milligrams of fluoride per litre of water.

The findings, by researchers from the University of Modena and Reggio Emilia, Italy, were based on analysis of data from 30 previous studies on fluoride and IQ.

In their report they warned: ‘Overall, most studies suggested an adverse effect of fluoride exposure on children’s IQ, starting at low levels of exposure.’ (Low was defined as 1mg/litre).

Animal studies also hint that fluoride exposure can damage memory and anecdotal evidence suggests some adult human sufferers are mentally sharper when they avoid it.

The Department of Health and Social Care – in a policy document from 2022 – states that although fluoride in water can increase the risk of fluorosis (permanent mottling of the teeth caused by disrupting the way that calcium is stored and distributed though the enamel) it’s not otherwise harmful to health.

A spokesman for the DHSC told Good Health: ‘Water fluoridation is a safe and effective public health measure that reduces tooth decay.

‘Prevention is always better than cure, and this government is committed to helping people stay healthy and keeping kids out of hospital.’

The DHSC added that future decisions on water fluoridation across the country will be on a ‘case-by-case’ basis.

However, the campaign group Freedom from Fluoride Alliance disagrees and claims there are more than 400 studies from around the world that show adding the mineral to water supplies is damaging to the developing brain.

It wants fluoride removed from both drinking water and toothpaste (most popular brands include it) and a greater emphasis on sugar-free diets to tackle Britain’s dental decay instead. (The devolved governments of Scotland, Wales and Northern Ireland have chosen not to add it, either because of the cost or because, in some areas, fluoride already occurs naturally in drinking water.)

‘Studies show there’s a strong correlation between fluoride over-exposure in the womb and from formula milk and reduced IQ in children,’ Joy Warren, spokesman for the lobby group, told Good health.

‘And in the UK we add more of it to water than they do in the US – 1mg per litre compared to 0.7mg there.

‘So any reduction in intelligence as a result of this exposure will be greater in the UK.

‘Even women who are pregnant should not be drinking fluoridated water because of the risk to their child.’

Warren, a retired environmental scientist, says children should not be allowed to use fluoride toothpaste either, as any that they swallow could find its way to the brain via the bloodstream, potentially harming their IQ.

But Dr Ben Atkins, past president of the Oral Health Foundation, one of the UK’s leading dental health charities, and a dentist in Manchester, insists there are no risks to children from using fluoride toothpaste.

He told Good Health: ‘I’m not worried about it – I give it (fluoride toothpaste) to my children and if I thought it was at all harmful it would not be allowed anywhere near them.’

But is fluoridation the best approach anyway? Dr Atkins and other experts think the UK might be better served to concentrate on boosting dental health by removing sugar from the diet rather than adding minerals to our water.

‘It is a form of mass medication and there are other options – if we can improve diet considerably and reduce sugar consumption we can reduce the need for water fluoridation.’

A report in October by the renowned Cochrane Centre – a body which analyses evidence on health policies – concluded that extending water fluoridation in the UK is likely to have limited effect in terms of bolstering dental health.

It reviewed evidence from 157 studies on the impact of adding fluoride to water and concluded that expanding it might increase the number of children with no tooth decay by about three per cent – but is just as likely to have no benefit at all, largely because most now get what they need from their toothpaste.

And a review published in Evidence-Based Dentistry in September 2024, by researchers at Trinity College Dublin, found the financial gains – in terms of fewer NHS treatments from fluoridated water – were marginal.

It showed that almost £100 had to be spent on adding the mineral to water just to prevent a single invasive dental treatment – such as drilling a rotten tooth.

Janet Clarkson, a professor of clinical effectiveness at Dundee University and one of the authors of the recent Cochrane report, said: ‘Water fluoridation can lead to small improvements in oral health.

‘But it doesn’t address the underlying issues, such as high sugar consumption and inadequate oral health behaviour.’