Fluoride in Our Drinking Water May Not Be as Useful as It Used to Be

The benefits of putting fluoride in our drinking water might have weakened over time. In a new review of the evidence, scientists have found that while water fluoridation may still slightly reduce the risk of cavities in young children, its overall impact is likely smaller than it was 50 years ago, before fluoride was widely available in toothpaste.

Starting in the 1950s, states and cities across the U.S. began adding fluoride to drinking water supplies, following research showing that fluoride can prevent tooth decay, especially in children. Today, water fluoridation is practiced in many other countries, and it has been lauded as one of the more effective public health interventions in modern times. But there has long been debate about the exact benefits of water fluoridation, and whether they could be outweighed by potential risks. Researchers with the Cochrane Library, a research organization well respected for its comprehensive reviews of clinical trial data related to important public health topics, have now decided to take a close look at fluoridation using the most recent gold standard evidence available.

The researchers newly examined 22 studies on community water fluoridation programs, making sure to differentiate between studies conducted before and after 1975, which is when fluoride began to be widely added to toothpaste products. They focused on a specific question: whether the introduction or loss of these programs affected people’s risk of cavities. Overall, they found that today’s programs may still lead to slightly less tooth decay in children’s baby teeth, and slightly more children free of tooth decay altogether. But they also found that the benefits of water fluoridation are probably smaller than they were prior to 1975.

“Contemporary evidence using different research methodologies suggest that the benefits of fluoridating water have declined in recent decades,” said review author Tanya Walsh, a professor of health care evaluation at the University of Manchester, in a statement from the Cochrane Library.

The newer studies in the review were conducted in high-income countries, the researchers note. People in many parts of the world still have very high rates of tooth decay and limited access to fluoride toothpaste or other preventive treatments. So new water fluoridation programs in these areas would likely still have a larger positive effect on residents’ tooth health. But the researchers add that much has changed over the past 50 years, and that the risks and benefits of these programs should be evaluated more closely from now on, especially in deciding whether to start a new one in places where they may be less needed.

“Oral health inequalities are an urgent public health issue that demands action. Water fluoridation is only one option and not necessarily the most appropriate for all populations,” Walsh said.

A previous Cochrane review found that these programs can likely raise the risk of dental fluorosis in young kids—a condition caused by too much exposure to fluoride that can cause discoloration of the teeth. Some recent studies have also found a potential link between fluoride exposure and worse kidney health in teens, as well as evidence that increased fluoride exposure in the womb is tied to a higher risk of children developing neurobehavioral issues by age 3. On the other hand, there are plenty of less supported beliefs about the harms of fluoridation, such as the idea that fluoride can raise cancer risk.

The major take-away from all this research and debate should be that science and the world around us is ever-evolving. In the best of times, we’re able to adapt to new evidence and act accordingly. It’s certainly possible that water fluoridation will stop being as worthwhile a public health measure as it once was. But that doesn’t necessarily negate the importance it had in the past.