A third government or international review discredits the false claims that fluoride harms the developing brain.

On June 2, 2021, the New Zealand Prime Minister’s Office released its latest review of water fluoridation.[1]  It found that fluoridation is safe and that it is effective in reducing cavities.

All government reviews have come to the same conclusion.

Indeed, they similarly determined that fluoridation is safe and effective. [2] 

The 2021 New Zealand review was likely prompted by a 2019 York University, Toronto report of a study [3] published in a prestigious journal.  The 2019 York report incorrectly concluded that women exposed to fluoride during pregnancy gave birth to boys of lowered intelligence.  

That claim was absolutely rejected by The New Zealand review. 

In fact, a long-term study conducted in New Zealand over the course of 38 years had already shown that fluoridation has no effect on intelligence. The study, Community Water Fluoridation and Intelligence: Prospective Study in New Zealand, had found no evidence of IQ or other cognitive effects in children due to fluoride exposure. [4]

Surprisingly, the well-designed New Zealand study was not cited by the weak York University study.  Did researchers not want readers to know about the strong study?

The claims advanced in the York University report had previously been rejected by the Canadian Agency on Drugs and Technologies in Health [5] in 2019 and a team of German researchers [6] in 2020.

The New Zealand review was led by the office of chief science advisor Professor Dame Juliet Gerrard. According to the New Zealand review, "there are no adverse effects of fluoride of any significance arising from fluoridation at the levels used here".

"Adding fluoride to water continues to have a positive impact by reducing the incidence of dental caries in […] New Zealand and is particularly important in reducing socioeconomic health inequities."

"Water fluoridation adjusts the natural level of fluoride in the water supply to between 0.7 and 1.0 parts per million. This is the optimal amount that helps prevent tooth decay and is recommended by the World Health Organisation."

This review comes as New Zealand is moving to a new system to govern decision-making about water fluoridation. The decision will now be taken by the director-general of health, Dr. Ashley Bloomfield, moving powers away from councils (local municipalities).

The equivalent change in Alberta would be to give Alberta’s Chief Medical Officer of Health decision-making power, taking it away from city councils.




[1] Office of the Prime Minister’s Chief Science Advisor (New Zealand)Fluoridation: an update on evidence, June 2, 2021.

[2] Gluckman et al., “Health Effects of Water Fluoridation: A Review of the Scientific Evidence. A Report on Behalf of the Royal Society of New Zealand and the Office of the Prime Minister’s Chief Science Advisor”, 2014.

[3] Green et al., “Association between Maternal Fluoride Exposure During Pregnancy and IQ Scores in Offspring in Canada” JAMA Pediatrics 173, no. 10 (2019).

[4] Broadbent et al., “Community Water Fluoridation and Intelligence: Prospective Study in New Zealand,” American Journal of Public Health 105, no. 1 (2015).

[5] Canadian Agency for Drugs and Technologies in Health (CADTH), “Community Water Fluoridation: A Review of Neurological and Cognitive Effects”, 2019.

[6] Guth et al., “Toxicity of Fluoride: Critical Evaluation of Evidence for Human Developmental Neurotoxicity in Epidemiological Studies, Animal Experiments and in Vitro Analyses,” Archives of Toxicology 94, no. 5 (2020).