A common sense guide to fluoride, the great dental conspiracy magnet

Fluorine compounds are all around us and can be found in everything from refrigerators and non-stick frying pans to dental floss and Prozac.

Why is fluoride good for your teeth?

Within the field of dentistry – the focus of this article – fluoride has scientifically proven benefits in helping your teeth combat tooth decay.

Dentists used to think fluoride strengthened the enamel when the teeth were still growing in the jaw (i.e. before they start protruding through the gums), but we now realise that the most important way in which fluoride strengthens the surface of the tooth is after the teeth have emerged into the mouth. This is because tooth decay is caused by the removal of minerals from the surface of your teeth – and fluoride stabilises and enhances the replenishment of these minerals, in a process known as remineralisation.

Is there a downside?

Although the wilder conspiracy theories quoted at the start of this article have little to no scientific basis, it is true that fluoride can have negative side effects, especially if it is swallowed (which we call a ‘non-topical’ application) rather than being applied to the surface of the tooth (a ‘topical’ application).

Swallowing and ingesting fluoride can lead to a lack of mineralisation of the tooth’s enamel known as ‘fluorosis’, which gives teeth a brown or white mottled appearance that is unfortunately permanent. (To give a sense of the scale of the problem, among populations whose water supply has been fluoridated, 12.5 per cent of people exhibit degrees of fluorosis that are of ‘aesthetic concern’.)

Although this mottling only affects the surface of the teeth, we dentists still consider it a serious side effect, not least because today, perhaps more than at any other time in human history, having a bright, confident smile is seen as an indicator of someone’s wider health and wellbeing.  

When and why was fluoride first added to the water supply?

Two pioneering American dentists working in the first half of the 20th century – Dr Frederick McKay and US Public Health Officer H Trendley Dean – are largely credited with determining both the beneficial and harmful effects of water fluoridation. In 1901, while working in Colorado Springs, McKay noticed that some of his patients’ teeth had signs of a condition known locally as “Colorado brown stain”. After further investigation, he found that their tooth enamel was hypocalcified, which means that it had a lower than expected mineral content. Normally, you would expect the enamel’s low mineral content to be linked to a greater susceptibility to tooth decay. To McKay’s surprise, this didn’t seem to be the case in Colorado Springs.

This intriguing combination of dental characteristics – stained teeth, a lower than expected mineral content in the enamel and yet no evidence of increased levels of tooth decay – was seen in children born within similar geographical areas, leading McKay to suspect that these geographical groupings were due to differences in the local water supply. Similarly, a change in the water supply in the Arkansas town of Bauxite caused an upsurge in mottled enamel and when the water supply was analysed a high level of fluoride was found (14.7 parts per million of fluoride). Other places in America showed the same correlation between instances of mottled teeth and high levels of fluoride.  

Although McKay had started to connect the dots between the levels of naturally occurring fluoride in drinking water, the mottling of tooth enamel and related rates of tooth decay, it was only in the 1930s that Trendley Dean was able to demonstrate a clear cause-and-effect relationship between the levels of fluoride in drinking water and the mottling of tooth enamel. His research culminated in the famous (if you’re a dentist) “21 City Study” which reported a 50 per cent reduction in tooth decay when fluoride levels in water were increased to one part per million (ppm).

As a result of McKay and Trendley Dean’s pioneering research, fluoride was first added to the public water supply in Grand Rapids, Michigan in 1945, to compare the subsequent levels of tooth decay in Grand Rapids to those in nearby and non-fluoridated Muskegon, which acted as a control. At the start of the study, both cities had similar rates of decay. But after six years with fluoride at 1ppm added to the water, the citizens of Grand Rapids had just half the levels of tooth decay experienced in Muskegon.

Fluoride was then added to the water in Muskegon to prove the point conclusively: adding fluoride to drinking water really did help take better care of people’s teeth.

However, many things have changed in the last 70 years, so should we still be adding fluoride to our water today?

Is fluoride being added to the UK water supply?

After those first successful trials in the 1940s, fluoride was added to water more widely across the United States and around the world. Today, just under 60 per cent of Americans receive fluoridated water yet, globally, the figure is far lower, at just under six per cent.

Many of the patients we speak to assume that fluoride is being added to their drinking water but, although fluoridation trials were conducted in the UK in the 1950s, just 10 per cent of the water supply across England and Wales contains between 0.5 and 1ppm of fluoride, either because the fluoride is naturally occurring or as an additive.

Today, 1.5 million people in England and Wales receive water from the ground that is naturally high in the mineral and another five million in parts of the West Midlands, Yorkshire and Tyneside receive artificially fluoridated water.

Fluoride is not added to the water in Scotland, Wales or Northern Ireland. You can see a map illustrating the extent and levels of water fluoridation across the UK here.

So why do so many people object to fluoride being added to their water?

The major overarching objection is ethical: water fluoridation is, after all, a rare instance of government-orchestrated mass medication, in which citizens aren’t asked for their consent or able to opt out (except by drinking bottled water). Fluoride is effectively being added to drinking water as a medicine, and has been legally recognised in the UK as such. Imagine the public outcry that would follow if the government started unilaterally adding other medicines (such as statins, for instance) to our drinking water.

Beyond this ethical dilemma and the aesthetic issue of fluorosis (teeth mottling), there are a number of other reasonable medical objections to water fluoridation. These include: that the doses of fluoride individuals receive cannot be controlled, and go to everyone using the water supply, regardless of their age or state of health; that fluoride accumulates in the body over time, especially in the bones and the pineal gland in the brain (which regulates the release of some hormones, including melatonin); that fluoride can affect the functioning of the thyroid gland; there is also some academic research to suggest that fluoride may damage the brain and lower IQ levels; fluoride has also been linked to occurrences of bone damage, arthritis and cancer.

(If you would like to find out more about these and other objections to fluoride, Dr Paul Connett has compiled a comprehensive though unashamedly crusading 50 reasons to oppose fluoridation.)

Most of the scientific studies and academic research investigating the wider effects of fluoride on humans are complex and their conclusions remain the subject of ongoing debate. Very few experts would claim that water fluoridation is a major public health risk but it is easy to see how legitimate research into fluoride’s potential side effects, when combined with the fact that water fluoridation schemes are typically imposed top-down by governments, has sown the seeds of the wilder conspiracy theories about fluoride found online.

So why is only 10pc of the UK drinking fluoridated water? What about the rest of us?

There is a simple, one-word answer to explain why water fluoridation has not become a universal practice in the developed world: toothpaste. Fluoride was first added to toothpaste in 1914 but it was only in 1955 that the first commercial fluoride toothpaste (Crest) became available. Most toothpaste now contains fluoride, and its widespread use is the main reason for the significant decline of tooth decay in the developed world over recent decades. We now recognise that the protection that fluoride provides teeth is best achieved by lifelong topical applications – i.e. brushing your teeth – while also limiting the risk of toxicological side effects, such as dental fluorosis.

Fluoridated water supplies in developing countries where people do not have access to fluoride toothpaste can still play a positive role in tooth care. But a government’s ultimate goal should be improving access to affordable fluoride toothpaste, as this is where topically applied fluoride is at its most effective.

(For more information about brushing, including practical tips, read our guide to the best way to brush your teeth.)

How can I take care of my teeth without exposing them to fluoride?

The most recent major national dental health survey (conducted in 2009) found that 94 per cent of adults in the UK used fluoride toothpaste – which leaves six per cent, or around four million people, whose teeth aren’t being exposed to fluoride on a regular basis.

If you are reluctant or resistant to the idea of using fluoride, there are other steps you can take that will also have a positive impact on your dental health. These include: going for regular check-ups with your dentist and hygienist; adapting your diet, especially to reduce your intake of extrinsic sugars (i.e. those that aren’t derived from fresh fruit or vegetables); and using dental health products that contain Xylitol, a natural sugar-free sweetener that reduces the build-up of plaque on the surfaces of teeth. (Xylitol can be used in toothpastes but is most beneficial when taken in regular doses throughout the day in the form of sugar-free chewing gums or mints.)

However, none of this is to downplay the importance and effectiveness of regular brushing. We can only hope that this article has persuaded you of the benefits of using a toothpaste containing fluoride – without us dentists having to slip something into your drinking water.

Dr. Mike Heffernan and Dr. Toby Edwards-Lunn are practising dentists with more than 50 years’ combined experience. They are also the inventors of Dr. Heff’s Remarkable Mints, a sugar-free mint that cleans and restores teeth and is endorsed by Toothfriendly International