By Dave Woodward

Dr John Colquhoun trained as a dentist in New Zealand and eventually became Principal Dental Officer for the Department of Health in Auckland, when he was one of the country’s most active and articulate advocates of water fluoridation.

In the course of seeking evidence that would support fluoridation of all of New Zealand’s public water supplies, he concluded that despite what he’d been trained to believe, the evidence just didn’t stack up.

Hi was editor of ‘Fluoride’, the quarterly journal of the International Society for Fluoride Research.

Study Tour

In 1980 John Colquhoun was sent on a world study tour which was intended to fit him for the role of expert fluoridation advocate.

His job would be to persuade those areas of New Zealand that still resisted fluoridation to join the other side.

Just before he left, his superiors confided in him some disturbing information. Initial results from a survey of School Dental Service records did not back up the claims made for fluoride. Still, his superiors were confident that when all the results were in, the true picture would emerge, and they set about collecting this information while he was away.

Overseas, in North America, Britain, Europe, Asia and Australia, though he visited only pro-fluoridation research centres and scientists, much the same information was surfacing wherever he went: tooth decay was declining equally in areas without fluoridation. He was assured however, that more extensive and thorough surveys then being carried out would bear out their position on fluoride, and they promised to send him the results.

Not to be made public

He came back to New Zealand and consulted the figures that had been prepared for him while he was away. Significantly fewer filling had been required in the non-fluoridated areas of his district than in the fluoridated areas.

When the returns for areas north and south of the city arrived, giving him a population sample of a quarter of the country’s population, a similar pattern appeared. Virtually no difference between fluoridated communities and those without fluoride in the water.

He requested statistics for the rest of the country and they were provided together with a warning that they were not to be made public. Again the picture was much the same.

Alternative sources of fluoride?

He continued to collect information and in 1985 and 1987 published research analysing social and regional patterns for tooth decay. The same slight advantage for non-fluoridated areas continued to appear.

At first he was convinced that the children in non-fluoridated areas must be obtaining fluoride from alternative sources, such as tablets, toothpaste, mouthwashes and so on. Again he went after information that might substantiate the effectiveness of fluoride.

Tooth decay dropping long before fluoridation

A study of tooth decay in five year olds since 1930 showed that the decline in decay rates had been more or less steady over sixty years.

Between 1960 and 1965 just over half the population of New Zealand changed to fluoridated water. Halt the 1970 five year olds had been drinking fluoridated water all their lives, yet there is not a trace of any benefit on the graph (see illustration). By 1975, 40 per cent of all toothpaste sales were of fluoridated toothpaste. Again, five years later, not a blip on the graph.

And the tooth decay rate continued to decline.

Whatever was causing it to decline, it apparently wasn’t fluoride. Dr Coloquhoun today admits he has no answers, but looks at the advent of household refrigeration, the increased intake of fresh fruits and vegetables, and the eightfold increase in cheese consumption as likely possibilities.

The big picture

He wrote to his colleagues in America for the promised figures and received no reply. When they were eventually published, they demonstrated little of no difference between fluoridated areas and non-fluoridated areas.

Later, in Arizona, Professor Steelink, charted the dental status of all (26,000) school children in the Tuscon area. He plotted incidence of tooth decay against neighbouring drinking water fluoride levels and found a positive corelation. The more fluoride a child drank, the more cavities appears in his teeth. Results from a similar survey in Missouri showed the same pattern.

Indian research involving 400,000 children showed tooth decay increasing with fluoride intake. Indian researchers concluded that local tooth decay was a function of dietary calcium deficiency and an excess of fluoride.

…a more sinister note began to sound. Not only was fluoride not doing any good; an increasing flow of evidence suggested the real possibility of harm… hip fracture… Downs Syndrome… diminished intelligence… bone cancer… and the jury is out on Alzheimer’s disease.

Recommended doses lowered

When he discovered evidence of dental fluorosis among Auckland school children, Colquhoun carried out research which showed 25 per cent of school children in fluoridated Auckland had dental fluorosis, with 3 per cent showing the more severe discoloured form. In the non-fluoridated areas, only those children taking fluoride tablets at the recommended dosage had the same degree of dental fluorosis. He published his research in 1984 and the following year it was confirmed by a follow up study by others.

The recommended dosages of fluoride tablets were drastically reduced, and parents were advised to reduce the amount of fluoride toothpaste their children used to brush their teeth, They were cautioned not to allow their children to swallow fluoridated toothpaste.

Classic studies flawed

He began to take a harder look at the classic studies on fluoride safety, and found many serious flaws. Even in New Zealand he found serious deficiencies. When Hastings was fluoridated, the method of diagnosing tooth decay was changed at the same time so that surface pitting was not classified as decay unless it actually penetrated the outer enamel layer of the teeth. This change in diagnostic methods was not recorded in published reports, which made much of the “improvement” in tooth decay rates following fluoridated.

Napier, with identical water in all respects except for fluoride was to be a control city to underline the improvement. Even with diagnostic methods unchanged, Napier began to demonstrate a better decline in tooth decay rates than Hastings, and was dropped from the experiment.

A South Island study of four communities chose an unfluoridated community with high rates of decay. The randomly selected children whose teeth were examined reflected the overall pattern of their communities. Tooth decay rates vary widely in both fluoridated and non-fluoridated areas. A different selection would conceivably have borne out the opposite view. The authors, when questioned by Colquhoun, replied that their results were consistent with other studies in professional dental journals.


Colquhoun comments that dentists in training are typically given only the pro-fluoride perspective, and are encouraged to believe that only misinformed lay people and a few crackpot professionals support the opposite view.

He does not imply there is any deliberate attempt to deceive – merely that these are people who are so sure they are right that they can fool themselves and confidently persuade others to accept that what they are doing is valid science. Colquhoun also remarks that a tendency for many pro-fluoride studies is to be small scale and selective.


From being an ardent advocate of fluoridation, Colquhoun came to believe just as firmly that it was not doing what was claimed for it.

Now , in addition, a more sinister note began to sound. Not only was fluoride not doing any good; an increasing flow of evidence suggested the real possibility of harm as a result of increased daily exposure to fluoride. Many environmentalists were becoming concerned at the build-up in harbours and waterways of fluoride.

Much recent research supports Colquhoun’s early suspicions of harm.

Reports of higher rates of hip fracture inf fluoridated areas have been received from widely separated areas around the world. 

Research has linked fluoridated water supplies with a significantly higher rate of Downs Syndrome births among younger women.

Reports from China suggest strongly that fluoride is associated with diminished intelligence levels. (This is in line with the findings by Phyllis Mullenix in the USA).

A rare bone cancer is up to seven times more common in young men in fluoridated areas of the USA. This also repeats the findings of animal research, though as yet, no firm link has been established.

Also, animal experiments have shown a disturbing tendency for fluoride to form chemical bonds with aluminium at low concentrations, and bypass normal cell barriers to deposit in brain tissue in a pattern similar to that found in suffers from Alzheimer’s disease. Once again, the jury is out.

Emperor’s new clothes

Most countries have rejected fluoride. Some have banned it. Only those with strong US links still maintain fluoridation as a firm public policy.

John Colquhoun is one man who, in the face of considerable professional peer-pressure, has insisted on his right to check the emperor’s new clothes and report publicly on what he sees.

Footnote: Dr Colquhoun’s personal account of his investigations can be found in respected, peer-reviewed international journal “Perspectives in Biology and Medicine” 41, pp 29-44, 1997 published by the University of Chicago Press.