Fluoride does not adversely affect IQ development in
children, a Dunedin study just published in an academic
The study published in the American Journal of Public
Health used data from the Dunedin Multidisciplinary
Lead author Dr Jonathan Broadbent, a public health dentistry
specialist, said the research focused on fluoride exposure
during the first five years. After that age, IQ was
Dr Broadbent compared those who grew up in Dunedin suburbs
with and without fluoridated water. Use of fluoride
toothpaste and tablets was taken into account, and the study
controlled for other factors, such as socioeconomic status.
The researchers examined IQ and other cognitive skills
between 7 and 13, and at age 38.
IQ information was available for 992 and 942 study members in
childhood and adulthood, respectively.
''Our analysis showed no significant differences in IQ by
fluoride exposure, even before controlling for the other
factors that might influence scores.
''In line with other studies, we found breast-feeding was
associated with higher child IQ, and this was regardless of
whether children grew up in fluoridated or non-fluoridated
Dr Broadbent said studies showing adverse effects from
fluoride were poorly designed.
''In comparison, the Dunedin Multidisciplinary Study is
world-renowned for the quality of its data and rigour of its
''Our findings will hopefully help to put another nail in the
coffin of the complete canard that fluoridating water is
somehow harmful to children's development.
''In reality, the total opposite is true, as it helps reduce
the tooth decay blighting the childhood of far too many New
Zealanders,'' Dr Broadbent said.
The findings were rubbished by opposition group Fluoride Free
NZ yesterday. National co-ordinator Mary Byrne disputed the
study's integrity, saying it appeared children taking
fluoride tablets were included with those drinking
''It appears they have included children taking fluoride
tablets in the already much smaller sample of children
drinking unfluoridated water. Children taking fluoride
tablets would have a similar dose of fluoride than the
children drinking fluoridated water.''
Ms Byrne said Dr Broadbent's public advocacy of fluoride's
oral health benefits meant the findings carried less weight.
Dr Broadbent rejected Ms Byrne's concern the unfluoridated
children included those taking fluoride tablets.
The study controlled for fluoride tablet intake, and also,
tablets were found to have no effect on IQ anyway.
He strongly rejected the suggestion he was not sufficiently
unbiased to lead the study.
The research team included other dentists, but also
psychologists and a statistician, Dr Broadbent said.
Dr Broadbent will speak about his findings to a psychology
conference in San Francisco later this week.