For decades, some activists have warned of links between fluoride and cancer. But years of research confirm that “there is no reason to believe that fluoride, used in an approved manner, causes disease in any way,” Herve Sroussi, DMD, PhDof Department of Oral Medicine and Oral Oncology at Dana-Farber and Brigham and Women’s Hospital.
Fluorides are compounds made from the element fluorine and other substances – usually metals, such as tin. Some fluoride occurs naturally in the environment, in water, air and soil, as well as in some foods of plant and animal origin. Once ingested, they enter the bloodstream and tend to accumulate in areas of high calcium content, such as bones and teeth.
In response to research showing that people whose drinking water had high levels of fluoride tended to have fewer cavities, some areas of the United States began adding fluoride to drinking water supplies in 1945. In 1962, the U.S. Public Health Service recommended public water supplies contain fluoride to reduce and prevent tooth decay. It is now used in the drinking water supplied to about 75 percent of Americans. Its cavity-preventing properties have led to its addition to many toothpastes.
“Fluoride is by far one of the best evidence-based approaches to reducing the risk of dental caries,” says Sroussi. Fluoride strengthens teeth by embedding itself in enamel, the outer layer of the tooth, where it draws minerals that strengthen the enamel structure.
Lack of link to cancer
Most of the more than 50 population studies investigating the possibility of a link between water fluoride levels and cancer have failed to find a strong link, American Cancer Society (ACS). The subject is inherently difficult to study, the ACS notes. Comparing cancer rates in a community before and after water fluoridation, or between communities with different levels of fluoridation, is not 100 percent reliable because the groups being compared may differ in the composition of the drinking water. Comparisons can also be difficult because different jurisdictions may use different types of fluoride or because residents may have used fluoridated water for different periods of time or at different ages.
In a review of numerous large-scale studies of water fluoridation and cancer rates, the International Agency for Research on Cancer found that the studies “showed a consistent trend for people living in areas with high water fluoride concentrations to have higher cancer. percentages than those living in low-concentration areas’. The agency also noted that the evidence was insufficient to conclude one way or the other. Similarly, the National Research Council, in a 1993 report, concluded that “available laboratory data are insufficient to demonstrate carcinogenicity [cancer-causing] effect of fluoride in animals’ and that ‘the weight of evidence from epidemiological studies completed to date does not support the hypothesis of an association between fluoride exposure and increased cancer risk in humans’.
Sroussi notes that if there is it was a link between water fluoridation and cancer would be relatively easy to detect scientifically, given the large number of people intentionally exposed to it. “Fluoridation is so pervasive around the world that if it had even the slightest effect on cancer rates, we would know about it by now,” he observes. “In areas where the drinking water has naturally high levels of fluoride, people tend to get dental fluorosis – staining and softening of the enamel – but do not experience increased rates of cancer.”
Fluoride treatments are often prescribed for cancer patients who are at increased risk of dental problems, Sroussi notes. Certain cancer treatments, such as radiation therapy to the head and neck, and certain types of chemotherapy, can reduce saliva production and cause mucositis, a condition that involves pain and inflammation of the gums and the lining of the mouth. These patients have an increased risk of tooth decay, which in some cases can progress rapidly. To guard against this, oncologists often prescribe fluoride supplements among other preventive measures to reduce the risk of a potentially rapidly developing deterioration of dental health.
For Sroussi, the benefits of water fluoridation for cavity prevention are also a matter of social justice and protecting vulnerable populations, including cancer survivors. Noting that people in wealthy areas tend to have access to good dental care, he comments that fluoridation is one of the best public health measures to reduce tooth decay in poorer populations.
Learn more about oral health from Oral Medicine and Oral Oncology at Dana-Farber Cancer Institute.
