Fluoridation of public water supplies offers no meaningful health benefit, according to a new study comparing cavity rates in two different Ontario provinces.
“Fluoridation is no longer effective,” said Hardy Limeback, head of the University of Toronto’s preventive dentistry program. Considering all the dangerous effects of fluoride consumption, in fact, he concluded that fluoridation is “more harmful than beneficial.”
Fluoridation, the addition of fluoride to public water supplies, has been popular in First World countries for more than six decades, and the U.S. Centers for Disease Control classifies it as one of the greatest health breakthroughs of the 20th century. Fluoridation proponents claim that the mineral strengthens teeth, thereby cutting cavity rate by 20 to 40 percent.
Yet the practice has always been controversial, primarily due to fluoride’s undisputed status as a highly reactive neurotoxin. More recent studies suggest that ingestion of fluoride can damage the thyroid gland and reduce children’s IQ levels. In 2006, a study published in Cancer Causes and Control found that exposure to large amounts of fluoridated water made seven-year-old boys four times more likely to develop a rare bone cancer known as childhood osteosarcoma.
In the new study, conducted on behalf of The Globe and Mail, researchers from Statistics Canada compared the tooth decay rates in the provinces of Ontario, which has Canada’s highest fluoridation rate, and Quebec, which has the lowest. Using data on more than 5,000 people, the researchers found no clinically significant difference.
Among children between the ages of six and 19, the tooth decay rate was only half a cavity higher in Quebec. The average number of cavities among children aged six to 11 was 1.76 in Quebec, compared with 1.7 in Ontario. In children aged 12 to 19, the absolute number of cavities increased but the difference did not; Ontario children averaged 2.35 cavities, compared with 2.79 in Quebec.
According to 2007 data, more than 75 percent of Ontario residents drink fluoridated water, in contrast with less than 6 percent of Quebec residents. Since the data were collected, the government of Quebec City has passed a law ending the use of fluoridation there.
Barring significant differences in rates of tooth brushing, bottled water consumption, or other relevant variables, the study suggests that the effectiveness of fluoridation has been strongly exaggerated.
All of Canada’s dental associations and its national health agency, Health Canada, officially endorse water fluoridation. In response to the Globe and Mail report, Health Canada immediately sought to cast doubt on the study, pointing out that it failed to assess individual fluoride intake and correlate that with cavity rates. Nevertheless, the agency admitted that the study data were accurate.
The Canadian study is not the first to cast doubt on the effectiveness of fluoridation. Recent studies have shown that cavity rates have declined at similar rates worldwide, independent of fluoridation.
“The parallel reduction in [cavities] in countries with a lot of fluoridation and countries with not much fluoridation is quite dramatic,” said Warren Bell, former head of the Canadian Association of Physicians for the Environment.
Although researchers in the 1940s believed that fluoride acted systemically in the body to strengthen teeth, more recent research suggests that it acts topically on the outside of the tooth. This means that brushing with fluoride toothpaste (which is then spit out) is both safer and more effective than drinking fluoridated water. Some scientists have therefore suggested that increased rates of tooth brushing, rather than water fluoridation, have led to improved dental health worldwide.
Other suggested causes include better overall oral hygiene (including flossing and more frequent brushing), lower sugar consumption, widespread use of antibiotics, and increased exposure to vitamin D in certain populations.
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