Fluoride is a naturally occurring substance found in rocks, many plants and water supplies that helps to protect teeth against decay. For this reason, it's also included in toothpaste, applied to teeth during dental check-ups and added to many drinking water supplies, a process called fluoridation.
Since fluoridation became widespread in Australia in the 1970s, rates of tooth decay in children have approximately halved. Fluoride is added to water at safe levels for human consumption, determined by the National Health and Medical Research Council (NHMRC) to be between 0.6mg and 1.1mg per litre.
Despite these safety measures, and its benefits to oral health, fluoridation continues to be controversial among a minority, who tend to back up their claims with selective 'evidence' that is inconclusive or erroneous. Following are some of the common claims against fluoride and why they are false.
Myth 1: Fluoride causes cancer
Fluoridation has been mistakenly linked to cancer risk since the publication of a 1990 study that observed a higher incidence of a rare form of bone cancer (osteosarcoma) in male rats exposed to high doses of fluoride.
These results have not been replicated since, and like many such studies, they involved a concentration of fluoride much higher than that found in municipal water supplies. Multiple reviews across the decades in many countries have concluded that there is no conclusive evidence that drinking fluoridated water causes cancer.
In Australia, the most recent systematic review of fluoride studies was conducted in 2017 by the NHMRC. The council did not find any link between fluoridation and cancer and recommended that fluoridation should continue.
In fact, people who don't receive enough fluoride from toothpaste, tap water and other sources could be at higher risk of another type of cancer, as there is growing evidence that poor oral hygiene may be a risk factor for developing oral cancer.
Myth 2: Water fluoridation lowers IQ
The 2017 NHMRC review also dismissed studies that claim to demonstrate a link between drinking fluoridated water and a decrease in IQ or cognitive function. These studies were found to be of limited quality and not relevant to the Australian context. The only study determined to be of high quality and relevance was a 2014 study that found no link between fluoridation and IQ.
Studies that claim to show such a link are often not peer-reviewed and ignore a number of factors that make their findings unreliable. Many come from deprived regions of China, India and Mexico and fail to account for exposure to other potentially hazardous substances such as arsenic or contaminated grain. Many are also based around concentrations of fluoride that are several times higher than that found in drinking water supplies in Australia.
Myth 3: Fluoride damages teeth
The only recognised negative effect of drinking fluoridated water is a minor risk of fluorosis. This is a rare condition that can affect children whose teeth are still developing, and involves the appearance of white lines on tooth surfaces. However, as a cosmetic issue, it does not affect the health or function of teeth.
The 2017 NHMRC review found that fluoridation may be linked to a slightly higher risk of mild fluorosis, but that there is no statistical difference in more severe fluorosis occurring in fluoridated or non-fluoridated areas.
What's more, dental fluorosis has actually declined over time. This may be thanks to the launch of low-fluoride children's toothpastes and improved awareness about the right amount of toothpaste to use, meaning young children today are exposed to less fluoride than those of previous generations.
Rather than damaging teeth, fluoride in drinking water is a safe and cost-effective way of improving oral health and lowering the rate of tooth decay and other dental problems in communities.
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 Australian Dental Association (ADA). Fluoride (31-64yrs) - Your Dental Health [Online] 2016 [Accessed August 2018] Available from: https://www.ada.org.au/Your-Dental-Health/Adults-31-64/Fluoride
 Australian Institute of Health and Welfare 2012. Australia's Health 2012: in brief. Cat. no. AUS 157. Canberra: AIHW
 Australian Dental Association (ADA). Fluoride [Online] 2017 [Accessed August 2018] Available from: https://www.ada.org.au/News-Media/Issues-at-a-Glance/Fluoride
 Cancer Council NSW. Fluoride in tap water does not cause cancer [Online] 2013 [Accessed August 2018] Available from: https://www.cancercouncil.com.au/86052/cancer-information/general-information-cancer-information/cancer-questions-myths/food-and-drink/fluoride-in-tap-water-does-not-cause-cancer/
 National Health and Medical Research Council. 2017 Public Statement – Water Fluoridation and Human Health in Australia [Online] 2017 [Accessed August 2018] Available from: https://www.nhmrc.gov.au/guidelines-publications/e44-0
 Australian Dental Association. Oral Cancer: How you're increasing your risk [Online] 2015 [Accessed August 2018] Available from: https://www.ada.org.au/getattachment/Your-Dental-Health/Resources-for-Professionals/Resources-for-Older-Adults-65/Oral-cancer-how-your-increasing-your-risk-(1)/ADA-YourDentalHealth-OralCancer_V1.pdf.aspx
 Jack, B., Ayson, M., Lewis, S., Irving, A., Agresta, B., Ko, H., Stoklosa, A. 2016, Health Effects of Water Fluoridation: Evidence Evaluation Report, report to the National Health and Medical Research Council, Canberra [Online] 2017 [Accessed August 2018] Available from: https://www.nhmrc.gov.au/_files_nhmrc/file/your_health/fluoridation/20160824_evidence_report_final_1.pdf
 Wisconsin Dental Association. Myth: Studies show that fluoride is linked to lower IQ scores in children [Online] 2013 [Accessed August 2018] Available from: https://www.wda.org/wp_super_faq/studies-show-that-fluoride-is-linked-to-lower-iq-scores-in-children