New Study Shows Little Evidence Fluoride in Drinking Water Prevents Cavities
Though authorities have added fluoride to public water supplies for decades under the guise of providing indisputable dental benefits, a startling new study reveals there is little scientific evidence to support this claim.
The Cochrane Collaboration, a group of doctors and researchers known for compiling comprehensive reviews of medical data, compiled every study on fluoridation they could find. After teasing out studies that lacked sufficient reliability or efficacy, the researchers analyzed the collective results.
Tellingly, they could find only three studies since 1975 that were well-designed and high-quality enough to be included. None of them demonstrated that fluoride prevented cavities. Anne Marie Glenny, the study’s co-author and a health science researcher at Manchester University, said,
“From the review, we’re unable to determine whether water fluoridation has an impact on caries levels in adults.”
The study did find that water fluoridation “resulted in a 35% reduction in decayed, missing or filled baby teeth and a 26% reduction in decayed, missing or filled permanent teeth. It also increased the percentage of children with no decay by 15%.” Though this implies a level of effectiveness, at least in children, the researchers cautioned that “the applicability of the results to current lifestyles is unclear because the majority of the studies were conducted before fluoride toothpastes and the other preventative measures were widely used in many communities around the world.”
The data’s lack of reliability was consistent. As Newsweek reported, “70 percent of the cavity-reducing studies made no effort to control for important confounding factors such as dietary sources of fluoride other than tap water, diet in general (like how much sugar they consumed) or ethnicity.”
Trevor Sheldon, Dean of the Hull York Medical School in the U.K., conducted a similar comprehensive review of fluoride’s dental benefits in 2000, reaching conclusions similar to the Cochrane findings: “I had assumed because of everything I’d heard that water fluoridation reduces cavities, but I was completely amazed by the lack of evidence,” he said. “My prior view was completely reversed.”
He added that “There’s really hardly any evidence” the practice works. “And if anything there may be some evidence the other way.” One Canadian study found that in a comparison of two neighboring towns, “when fluoridation was stopped in one city, cavity prevalence actually went down slightly amongst schoolchildren, while cavity rates in the fluoridated community remained stable.”
Sheldon remarked that that if fluoridation needed approval to be added to water today, “nobody would even think about it,” due to the shoddy evidence (and lack thereof).
Fluoride is added to ⅔ of American tap water, a process that began in 1945 when Grand Rapids, Michigan initiated the practice. It quickly spread across the country, largely due to perceptions that it was good for tooth health. Fluoride is linked to a variety of health issues, including impaired endocrine and brain function. It was recently linked to ADHD and underactive thyroid, though the Cochrane review studied only dental issues.
Predictably, the CDC refused to entertain the idea that fluoride is not effective at preventing cavities. “Nothing in the Cochrane review” deters the government’s “confidence in water fluoridation as a valuable tool to prevent tooth decay in children as well as adults,” Barbara Gooch, a dental researcher with CDC’s Division of Oral Health, said.
The refusal of the CDC to examine serious, valid concerns with a program that affects the health of millions of people is an unfortunate reflection of the government’s priorities. As Sheldon observed,
“When you have a public health intervention that’s applied to everybody, the burden of evidence to know that people are likely to benefit and not to be harmed is much higher, since people can’t choose,” Sheldon says. “Public health bodies need to have the courage to look at this review …and be honest enough to say that this needs to be reconsidered.”