Fluoride was first added to drinking water in the United States decades ago to help reduce and prevent tooth decay. Overwhelming research shows that there is no reason to believe that fluoride, when used in an approved manner, causes any disease, including cancer.
It is a naturally occurring mineral that can be found in soil, water, plants, and food. When ingested, it tends to accumulate in areas of the body that are high in calcium, such as the bones and teeth — preventing decay and promoting growth by drawing in minerals.
“Fluoride is by far one of the best approaches, from an evidence-based standpoint, of reducing the risk of dental decay,” says Herve Sroussi, PhD, MD, Director for Research of the Department of Oral Medicine and Oral Oncology at Dana-Farber and Brigham and Women’s Hospital.
The practice of adding fluoride to drinking water in the United States began in 1945, after American researchers found that people whose drinking water had naturally high levels of fluoride tended to have fewer dental cavities. The country then began to add the mineral to treated drinking water in some areas, and in 1962, the U.S. Public Health Service recommended that all? public water supplies contain fluoride to help reduce and prevent tooth decay.
Fluoride is now used in the public drinking water supplied to about 75 percent of Americans and has been incorporated into most kinds of toothpastes and other dental products such as mouth rinses.
Lack of a connection to cancer
Most population studies exploring the possibility of a link between fluoride and cancer have failed to find a strong connection, according to the American Cancer Society (ACS).
As with many large-scale population studies, the question is inherently difficult to address. There are many factors beyond fluoridation rates that can affect cancer rates from population to population. Simply comparing the cancer rates in two jurisdictions and the amount of fluoride in their water can lead to inaccurate conclusions. But Sroussi notes that if there were a connection between water fluoridation and cancer, it would still be relatively easy to detect scientifically, given the large number of people exposed to it.
“If it had the slightest effect on cancer rates, we’d know it by now,” he says.
Researchers have studied the subject extensively and most evidence shows little connection between fluoride and cancer risk. In a 1987 review of numerous population studies of water fluoridation and cancer rates, the World Health Organization’s International Agency for Research on Cancer found that there is “no consistent tendency for people living in areas with high concentrations of fluoride in the water to have higher cancer rates than those living in areas with low concentrations.”
Four years later, the National Research Council, the operating arm of the United States National Academies of Sciences, Engineering, and Medicine, similarly concluded that “the available laboratory data are insufficient to demonstrate a carcinogenic [cancer-causing] effect of fluoride in animals” and that “the weight of the evidence from the epidemiological studies completed to date does not support the hypothesis of an association between fluoride exposure and increased cancer risk in humans.”
Fluoride supplements are often prescribed for people with cancer who are at heightened risk of dental problems. Some cancer treatments, such as radiation therapy to the head and neck, as well as certain kinds of chemotherapy, can reduce saliva production and produce mucositis, a condition that causes pain and inflammation of the gums and inner lining of the mouth. These patients have a higher risk of tooth decay, which, in certain cases, can progress rapidly.
Based on early research, this also seems to be the case for people who are being treated with immune checkpoint inhibitors, a type of immunotherapy that is becoming increasingly commonplace in oncology.
Water fluoridation can be beneficial for vulnerable populations, including cancer survivors. Wealthier populations tend to have access to better dental care, Sroussi observes. Fluoridation as a public-health measure can reduce dental decay in areas that have been historically marginalized and face barriers to quality dentistry.