Experts question controversial study on fluoride in pregnancy

Australian experts have urged caution following the release of a new study that suggests there may be a link between higher fluoride exposure during pregnancy and children’s IQ.

The observational study, published in JAMA Pediatrics, followed 512 mother-child pairs across six Canadian cities with the aim of examining whether or not fluoride is a “potential neurotoxin”.

Experts have questioned the study into fluoride and child IQ.

Researchers collected maternal urine fluoride levels throughout their pregnancy and the women filled in questionnaires about fluoride consumption in their drinking water, food, toothpaste, tea and coffee.

The researchers then followed up with the women’s children when they were aged three and four for IQ testing.

As expected, the mothers who lived in towns with fluoride (40 per cent) in the water supply had higher concentrations in their urine and higher fluoride intake.

High levels of fluoride exposure (more than 1mg/L) was associated with a 4.5-point lower score in IQ, but only among the boys.

JAMA Pediatrics editor Dr Dimitri Christakis noted in an accompanying editorial that the "decision to publish this article was not easy", and that they subjected the study to "additional scrutiny".

Dr Christakis hypothesised the finding among boys may be due to developmental differences between boys and girls.

The study has caused heated debate among researchers who highlighted that a correlation, not causation, was found.

Some experts say there is no harm in pregnant women drinking filtered water.Credit:Stock

Besides, said Associate Professor Oliver Jones, an associate professor in chemistry from the School of Science at RMIT University, most of the women in the study had a fluoride intake below 1mg/L even if they lived in a town with fluoridated tap water. “Multiple previous studies have shown [this level] is safe," he said.

Professor Grainne McAlonan, of the Sackler Centre for Translational Neurodevelopment, King’s College London, added: “If you look at average IQ in the children from fluoridated and non-fluoridated groups these are virtually the same: 108.07 vs 108.21, respectively."

She added: "I would be very cautious about over-interpreting this data. Statistical significance does not equal ‘importance’."

Still, the findings deserve further examination.

"As the editorial in JAMA states, 'the hypothesis that fluoride is a neurodevelopmental toxicant must now be given serious consideration'," said Dr Mark Diesendorf,  an honorary associate professor in the Environmental Humanities Group at the University of NSW.

“It’s a complicated conversation,” Dr Christakis said, adding that it is possible from a public health standpoint that fluoride in water is beneficial to a child after they are born but not before.

“The Australian Dental Association’s position is consistent with the National Health and Medical Research Council which confirms that fluoride strengthens and protects teeth in people of all ages, and does so safely,” said the association's spokesman, Dr Michael Foley.

While other experts questioned the research and noted it was a single study, they largely agreed that more studies were needed.

Professor Michael Davies, a reproductive epidemiologist from the Robinson Research Institute at the University of Adelaide, said the design of the study made the “associations unreliable” but would like to see “more appropriately designed studies on the topic”.

In the meantime, some experts suggest pregnant women drink filtered water if they can.

“It’s also important to note that not all fluoridated water needs to be avoided, there was a dose-respondent relationship, so drinking small amounts of fluoridated water is not going to hurt,” said fertility and prenatal dietitian Melanie McGrice. “Water is still the best choice for us all, pregnant women included, to drink; it just might be beneficial to filter it during pregnancy."

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