What Does the Evidence Say About Fluoride Lowering IQ?

Fluoride is once again in the news, and for good reason. In a new review of data published this month, scientists found evidence that higher levels of fluoride exposure are associated with reduced IQ in infants and very young children.

Historically, fluoride has been added to our water to strengthen tooth enamel, which prevents cavities. Improving childhood dental health in turn reduces sick days missed from school, leads to less expensive dental procedures, and possibly lowers the risk of cardiovascular disease later in life.

But this new study, conducted by scientists at the NIH’s National Toxicology Program, suggests that fluoride exposure, and by extension water fluoridation, may be more risky than previously thought. They found that children exposed to higher levels of fluoride in their first years of life had significantly lower IQ scores than children exposed to lower levels of fluoride, especially between one and two points.

view, has been published in JAMA PediatricsIt’s not the only recent study to cast some shade on fluoride. For example, a study from last May found Association between higher exposure to fluoride in pregnant women and risk of their children being later diagnosed with neurobehavioral problems by age three. There are also some scientists recently questioned Since people in many parts of the world can get fluoride from toothpaste products, is water fluoridation necessary to get the benefits of excess fluoride?

The scientific debate about the pros and cons of fluorides is not one-sided. Some scientists there is criticized eg methodology and interpretations of recent research. And the research itself could not find definitive proof It associates low IR with low fluoride exposure, including recommended levels for drinking water in the United States (0.7 milligrams per liter). There are other reviews failed as well finding a link between relatively low fluoride exposure and IQ loss or developmental disorder (including after the introduction of a fluoridation program).

Some critics of fluoridation have tried to blame fluoride for other health problems, with less evidence supporting a potential link. Robert F. Kennedy Jr., who is poised to lead the U.S. Department of Health and Human Services under the Trump administration. argued Fluoride is linked to bone cancer, for example, despite the fact that most studies have found none significant cancer association.

For this Secret Survey, we reached out to experts to share their thoughts on the latest research, the science of fluoride, and the potential implications of this research. The answers below have been lightly edited and shortened for clarity.

Jay Kumar

A retired epidemiologist specializing in dental health and a meta-analysis 2023 on the potential IQ effects of fluoride in children.

Findings that high fluoride levels in drinking water in rural areas of China, India, Pakistan, and Iran are associated with IQ deficits are not new. The authors cannot link IQ deficits to fluoride in water because the quality of the research is low. These studies also measured fluoride in drinking water and children’s IQ. For example, high-IQ parents may have moved from regions to avoid high-fluoridation water due to its well-known risk to teeth and bones, and therefore, the absence of higher-IQ families may bias the association. . This potential bias is sometimes known as “the cart before the horse.” Also, animal and human studies cannot explain how fluoride affects the brain.

We published a study entitled “The association of low fluoride exposure with child intelligence: a meta-analysis of community water fluoridation.” In this paper, we answered the research question: Does fluoride exposure recommended for preventing tooth decay reduce children’s cognitive and IQ scores? A fluoride of 0.7 mg/L is recommended for US community water supplies.

Our study concluded that exposure to fluoride at approximately twice the concentration used in community water fluoridation (less than 1.5 mg/L) was not associated with lower IQ scores in children. However, we emphasize the need for more research to determine whether naturally occurring fluoride in drinking water greater than 1.5 mg/L causes IQ deficits.

A a recent Australian study Do et al. It confirmed findings from Canada, New Zealand and Spain that IQ scores were similar in fluoridated and non-fluoridated areas.

Bruce Lanphear

who is an epidemiologist at Simon Fraser University read how exposure to fluoride in pregnant women can affect the later development of their children.

Fluorine is a reactive chemical that strongly binds to calcium and metals. In 1944, the Journal of the American Dental Association described fluoridation as a “wonderful attraction” for preventing cavities, but warned of the risks of adding a “highly toxic substance” to drinking water. Today, more than 70% of Americans drink water with about 0.7 (parts per million, or ppm) fluoride, which is considered “optimal.” Fluoride is also found in toothpaste (1000-1500 ppm), black tea (1-6 ppm), foods such as sardines and anchovies (2-4 mg/100 g), some medications (eg Prozac, Lipitor), and pesticides. the product is treated like a raisin. Fluoride intake has increased over the past 50 years, leading to an increase in dental fluorosis – discoloration or staining of teeth caused by exposure to excessive fluoride during development.

What Did the Study Find?

Taylor’s team reviewed 74 studies from 10 countries that linked fluoride exposure to IQ scores. Although many of the early studies were of lower quality, a meta-analysis of high-quality research found that a 1 ppm increase in urinary fluoride was associated with a 1.2 point decrease in IQ in children, even at levels below 1.5 ppm. Although this IQ reduction is small, it has significant population-level implications, especially for children exposed to other toxic chemicals such as lead or air pollution.

Do these findings apply to fluoridated communities?

Critics claim that at water fluoride levels of less than 1.5 mg/l no IR deficiency is detected, but this is misleading. First, no obvious threshold was identified. Second, water fluoride is only one source of exposure, and total fluoride intake must be considered for risk assessment. Urinary fluoride, a snapshot of total fluoride intake, showed a significant reduction in IQ in children at concentrations typically found in fluoridated communities.

For example, a Canadian study found that 25% of pregnant women in optimal fluoride areas had urinary fluoride levels above 1 ppm and 5% above 1.5 ppm. Although some question the reliability of urinary fluoride measurements, they are widely used by epidemiologists to assess short-term exposure to chemicals such as fluoride and arsenic.

Does fluoridation protect against tooth decay?

It is time to critically review the benefits of fluoride. 2024 update A Cochrane review Studies conducted after 1975, when fluoride toothpaste became widely available, found no benefit from water fluoridation. The cavity-preventing effects of fluoride are mostly topical, not systemic, and have no benefit until the teeth erupt.

Should you be worried?

Public health agencies should revise fluoridation guidelines based on new evidence. Until then, consider these precautions:

• Pregnant women and young children: Avoid other sources of fluoride, such as fluoridated water and black tea.
• Infant milk: Use non-fluoridated water to mix formula; breast milk contains minimal fluoride.
• Children’s toothpaste: Use only a rice-sized amount of fluoride toothpaste and make sure children do not swallow the toothpaste.

By taking these steps, you can minimize the effects of fluoride during critical developmental periods.

Sarah Evans

Associate Professor of Environmental Medicine and Climate Science at the Icahn School of Medicine at Mount Sinai, studies how people’s early-life exposures can affect behavior and cognition.

It is important to note that none of the studies included in the (NTP) meta-analysis were conducted in the United States, where the recommended drinking water fluoride concentration is 0.7 mg/L – more than 50% lower than the fluoride exposure measured here. most of the communities read. Although more research is needed to examine the effects of lower levels of fluoride exposure, 2023 meta-analysis No association was found between fluoride and child IQ in communities with drinking water levels similar to those in the United States.

Although there are no studies to date showing the risk of harm from the 0.7 mg/L fluoride most commonly found in US drinking water, an estimated 2.9 million Americans and 180 million people worldwide may be exposed to levels of fluoride higher than WHO guidelines . the presence of high levels of natural fluoride in some areas. Individuals living in these areas may be at greater risk of exposure to levels associated with reduced child IQ in the study. In addition, the inclusion of fluoride in dental products and treatments, as well as its natural presence in some foods and beverages, may lead to exposures exceeding the daily recommendation. Comprehensive studies measuring individual exposure levels of the US population from all sources of fluoride are needed.

Although about three-quarters of water supplies in the United States are fluoridated, the practice is not mandated by the federal government and is under state or local control, so fluoridation practices vary widely across the country. For example, 99.9% of Kentucky residents receive fluoride in their drinking water, compared to only 16% of New Jersey residents. Individuals interested in finding out the level of fluoride in their drinking water should contact their water supplier. If you live in an area with high fluoride from natural sources and are pregnant or have young children, it is possible to reduce fluoride exposure through reverse osmosis filtration. Bottled water is not regulated for the presence of fluoride or other contaminants and is generally not recommended. If you consume water from a public supply or a private well that is not fluoridated, it is important to practice good dental hygiene by using fluoride toothpaste and mouthwash and visit the dentist regularly.

The results of this study may lead to more communities questioning whether to stop water fluoridation. Although there is some evidence that the increase in fluoride products and improved access to dental care has reduced the need for fluoridated water, several studies have shown a sharp increase in the need for dental treatments in communities that remove fluoride from drinking water and child tooth decay. , suggesting that water fluoridation remains an effective and necessary public health intervention.

Although a recent meta-analysis by Taylor et al. suggest adverse effects of high-level fluoride exposure on brain development, but also emphasize the need for well-designed longitudinal studies measuring individual-level fluoride exposure over time to confirm whether associations with IQ or other neurodevelopmental outcomes persist at lower levels. most Americans. In addition, it highlights the need to examine practices that reduce the risk of exposure to fluoride above recommended levels in areas with high natural fluoride levels and to reexamine practices that increase access to routine dental care.