Why Is There Fluoride in Water? Is It Effective?

A meta-analysis of all the studies on the dental health implications of vegetarian diets showed significantly fewer decayed teeth, missing teeth, and the number of teeth with fillings. One of the studies that bucked the trend and showed that vegetarians had more cavities blamed the excess decay on the fact that vegetarians were significantly less likely to choose fluoride-containing toothpaste, supported by the fact that those who did use toothpaste with fluoride had significantly fewer decayed teeth than those who didn’t.

Fluoride is thought to protect teeth by improving the intrinsic stability of the mineral structure of dental enamel. A recent meta-analysis of nearly 100 randomized controlled trials of fluoride toothpaste involving more than 10,000 people found “high-certainty” evidence that toothpaste containing the typical amount of fluoride reduces tooth decay significantly more than non-fluoride toothpaste in both children and adults. But what about the addition of fluoride to the water supply?

A medical consensus of public health authorities around the world has considered water fluoridation at appropriate levels as a safe and effective means to prevent cavities on a community-wide scale. In fact, the CDC, the US Center of Disease Control and Prevention, deemed fluoridation of drinking water as one of the top ten public health achievements of the 20th century. However, community water fluoridation has long been a flashpoint of polemic and polarization. Anti-fluoridation activists underscore that there is no human dietary requirement for fluoride and argue that water fluoridation isn’t effective enough to justify the costs, which may include health risks.

First, some background before I dive into the controversy. Fluoride is a mineral element in the Earth’s crust that naturally occurs in most water supplies. This is one of the reasons fluoridation has withstood Constitutional challenges. Courts have ruled that, rather than an added medication, fluoride can be seen as a nutrient found naturally in some areas but not others, and fluoridation of water supplies is a matter of just leveling the playing field, particularly for poor communities who may have limited access to dental care. Fluoridation can be defined as “the upward or downward adjustment of the level of fluoride content in drinking water to an optimal level just enough to prevent cavities but not enough to cause fluorosis,” or cosmetic changes in the teeth.

It all started in 1901 with an investigation into Colorado Brown Stain, “grotesque” brown stains on the teeth of Colorado Springs residents. At the same time, teeth afflicted by the condition were “surprisingly and inexplicably resistant to decay.” After fluoride was identified as the basis for these changes, a nationwide survey of fluoride levels in drinking water in the 1930s led to the discovery that fluoride could reach levels around 1 part per million without causing serious fluorosis. Hoping to get the best of both worlds, Grand Rapids, Michigan, in 1945, became the first city in the world to fluoridate its water supply. Within 11 years, cavity rates among children in Grand Rapids were reportedly down more than 60 percent, and a fluoridation movement was born. Today, about two dozen countries fluoridate their drinking water. Dozens of others have naturally fluoridated water or instead add fluoride to milk or table salt.

Fluoridation pushback started almost immediately in the United States. The obsession of Dr. Strangelove’s Colonel Ripper with the purity of his “precious bodily fluids” was based on real-life right-wing Red Scare conspiracy theories that fluoridation was meant to produce “moronic, atheistic slaves” who would bow to the communists.

Today’s social media is also rife with anti-fluoridation messages. Studies have found that 63 percent of Instagram posts regarding fluoride could be classified as anti-fluoride, 64 percent of tweets on Twitter, 99 percent of YouTube videos, and up to 100 percent of fluoride groups and pages found on Facebook were anti-fluoride. Years before COVID, the antifluoridation crusade was considered a case study of “digital pandemics of public health misinformation.” In the year before COVID, the first worldwide survey of the crisis of confidence in science of 140,000 people in 140 countries found that only 18 percent of humanity appeared to have a “high” level of trust in science. To my pleasant surprise though, despite so many institutional failures, a 2020 follow-up of the survey found trust in science actually increased after COVID.

Where does the science land on water fluoridation? First, let me address efficacy. The CDC attributes the steep decline in dental decay in the United States in the latter half of the 20th century to water fluoridation, but similar declines were noted in non-fluoridated countries, attributed in large part to the widespread global distribution of fluoride toothpaste. The best evidence we have comes from prospective studies with concurrent controls, comparing cavity rates over time in fluoridated versus non-fluoridated populations. There have been more than 100 such studies to date, and overall, fluoridation results in a 35 percent fewer decayed, missing, or filled baby teeth and 26 percent fewer decayed, missing, or filled permanent teeth. So, community fluoridation does indeed help to cut down on cavities. The question then becomes, at what cost?, which we’ll discuss next.