When you take a supplement, you know exactly what you’re ingesting and what health benefits you stand to gain. And yet, a majority of Americans take a fluoride supplement automatically every time they drink water.
Fluoride is a naturally occurring mineral that is released from rocks into the air, water, and soil. It is also commonly produced as a byproduct of phosphate fertilizer production (yes, creepy) in the form of fluorosilicic acid (FSA).
Water that is naturally fluoridated or, as in most cases, has FSA added to it, helps prevent tooth decay. In fact, fluoride had done so much for dental health that the Centers for Disease Control and Prevention named the fluoridation of community water systems as one of the ten great public health achievements of the 20th century.
However, community water fluoridation is not without controversy. Hundreds of cities—ranging from Portland to Wichita—have voted against putting fluoride in drinking water. And recent research—including an August 2019 study linking prenatal fluoride intake with a decrease in child IQ—has raised some major concerns surrounding this commonly accepted supplement.
Why do we put fluoride in water?
Scientists in the 1930s observed that children who drank water naturally high in fluoride suffered less tooth decay and fluoride was first added to public water supplies in 1945, in Grand Rapids, Michigan. The dental health of Grand Rapids school children was studied for years, and a 15-year study from 1962 reported about a 60% reduction in child tooth decay with “no undesirable effects.”
The Grand Rapids study opened the gates to water fluoridation, and today the practice has expanded to cover 74.4% of Americans who get their water from community water systems. The Department of Health and Human Services’ Office of Disease Prevention and Health Promotion has the goal of increasing this number to 79.6% by 2020.
The science of fluoridation: timeless or outdated?
In June 2015, independent research organization Cochrane published a research review of 20 studies on fluoridated water and tooth decay. Of those studies reviewed, about 70% were conducted before 1975.
The review found that water fluoridation resulted in 35% less tooth decay in children but did not show any benefit for adults. However, much of the research into the benefits of fluoride is dated, and recently there has been more research scrutinizing these decades-old studies. The Cochrane study authors noted that they “had concerns about the methods used […] in 97% of the studies.”
The benefits of fluoridation: correlation or coincidence?
Globally, many countries either do not fluoridate their water, or fluoridate at levels much lower than the U.S. Only 38% of Canadians receive fluoridated water, and for Europeans that number is far lower, with only about 3% receiving treated drinking water.
Countries with fluoridation have seen a measured decrease in the incidence of childhood tooth decay over the past 40 years. However, countries without fluoridation have also seen a similar decrease in tooth decay. This suggests that while global dental health is improving, we may not have fluoridated water alone to thank.
Is fluoridating water really necessary?
Fluoride strengthens tooth enamel. But fluoridating water may not be the ideal way to obtain fluoride and may come with unwanted risks. A study from 2018 concluded that because “the fluoride benefit is mainly topical,” it may be better to use a product such as fluoride toothpaste or mouthwash as opposed to ingesting fluoridated water.
In recent years, even government policy has changed. In 2015, the U.S. Public Health Service reduced its own recommendation for fluoridation level from 0.7-1.2 mg/L to 0.7 mg/L.
Risks of fluoride overexposure
Dental fluorosis is a condition resulting in white spots appearing on tooth enamel. It affects children under the age of 8 who take in too much fluoride when their permanent teeth are still developing. Incidence is very rare in community with a fluoridation level less than 2.0 mg/L.
Skeletal fluorosis is a condition of excessive fluoride accumulating in the bone due to high-level exposure over many years. Fluorosis is endemic in 25 countries, affecting large populations in India and China. It is rare in the U.S.
Does fluoride lower IQ in children?
There have been over 50 studies performed worldwide that measure the relationship between fluoride intake and reduced IQ in children. Recent analyses of regions in Mexico, India, and Kenya with naturally high fluoride levels in groundwater showed that higher fluoride levels correlated with lower IQ.
However, these studies have largely pertained to children exposed to naturally occurring fluoride. It wasn’t until recently that a study found similar results due to fluoridated water.
Canadian study finds relationship between fluoridated water and decreased child IQ
Published in August 2019, a Canadian study was the first to investigate the relationship between IQ and intentional community water fluoridation.
The study followed approximately 600 mother-child pairs from pregnancy to when IQ was assessed at ages 3 to 4. It found that a 1 mg higher daily intake of fluoride during pregnancy was associated with a 3.66 lower IQ score in both boys and girls.
The Journal of the American Medical Association published an accompanying editorial acknowledging that while more research is needed, the study is important in raising the question of fluoride potentially being a neurotoxin. In the meantime, study author Christine Till concludes: "We recommend that women reduce their fluoride intake during pregnancy."
Considering your fluoride intake
Is the water you’re drinking fluoridated? Rates of fluoridation vary from state to state. Centers for Disease Control offers an online tool that informs residents of participating state if their community water is fluoridated.
Naturally occurring fluoride is also found in varying concentrations in water everywhere. You may furthermore encounter fluoride in dental products such as toothpaste and mouthwash, or in foods produced using fluoridated water.
If you’re concerned about your fluoride intake, you may be relieved to know that while research into fluoride’s risks is ongoing, some experts say there’s little to worry about.
Expert response to fluoride concerns
In response to the Canadian IQ study, Grainne McAlonan, professor of translational neuroscience at the Sackler Institute for Translational Neurodevelopment at King's College London, said, “I would be very cautious about over-interpreting this data.”
McAlonan points out that while the study found a 1 mg higher dose of fluoride resulted in lower IQ, that dosing isn’t a real-world consideration. “In reality the average difference in fluoride levels between the majority living in low and high fluoride areas is nowhere near 1mg/L.”
Further, she pointed out that the average IQ of children from fluoridated and non-fluoridated groups is nearly the same: 108.07 vs. 108.21. In other words, when it comes to fluoride and a decrease in IQ, there may not be a significant enough difference to worry about it.
If you’re an American adult (or Irish or Australian, among others), you’ve likely been drinking fluoridated water all your life. While there has been more study into the controversy in recent times, more research is needed into the potential risks.
For now, Centers for Disease Control continue to recommend the practice of fluoridation as a measure to prevent tooth decay in children. While some experts say pregnant women may want to exercise caution, others say the risks are overblown.
If you live in an area with community water fluoridation, filtration is an option for those who want it. For the rest of us, keeping up to date with studies showing both benefits and risks of fluoridation may simply be another thing to keep in mind whenever we pour a glass from the tap.