What does the evidence say about fluoride lowering IQ?

Fluoride is in the news again, and not for good reason. In a new review of data published this month, scientists found evidence that higher levels of fluoride exposure are associated with lower IQ in infants and very young children.

Historically, fluoride was added to water to strengthen tooth enamel, which helps prevent cavities. Improving children’s dental health in turn is known to reduce sick leave outside of school, lead to less expensive dental procedures, and may reduce the risk of cardiovascular disease later in life.

But this new research, conducted by scientists at the National Institutes of Health’s National Toxicology Program, suggests that fluoride exposure — and thus water fluoridation — may be more dangerous than assumed. They found that children who were exposed to higher levels of fluoride during the first years of their lives had significantly lower IQ scores, specifically between one and two points, compared to children who were exposed to lower levels of fluoride.

review, published in JAMA Pediatricsisn’t the only recent study to cast some shade on fluoride. A study conducted last May, for example, Found There is a link between high fluoride exposure in pregnant women and an increased risk of their children being later diagnosed with neurobehavioral problems at age three. Some scholars have also done so He was recently questioned Whether water fluoridation is needed to get the benefits of fluoride anymore, as people in many parts of the world can get fluoride from their toothpaste products.

However, the scientific debate about the pros and cons of fluoride is not one-sided. Some scholars He owns criticize For example, the methodology and interpretations of the latest review. The study itself did not find Conclusive evidence Low IQ has been linked to lower exposure to fluoride, including recommended levels for drinking water in the United States (0.7 milligrams per liter). Other reviews have Likewise failed To find a link between relatively low exposure to fluoride and loss of IQ Poor development (Included After introducing the fluorescence program).

Some critics of fluoridation have also tried to blame fluoride for other health problems that have much less evidence to support a possible relationship. Robert F. Kennedy Jr., who is set to head the US Department of Health and Human Services under the Trump administration, Argue For example, fluoride is linked to bone cancer, although most studies have found not High association with cancer.

In this Giz Asks article, we reached out to experts to share their thoughts on the latest study, the science surrounding fluoride, and the potential implications of this research. The following responses have been lightly edited and condensed for clarity.

Jay Kumar

A retired dental epidemiologist and co-author of A Meta-analysis In 2023 on the possible effects of fluoride on children’s IQ.

Findings that high levels of fluoride in drinking water in rural areas of China, India, Pakistan, and Iran are associated with IQ deficits are not new. The authors cannot attribute the IQ deficit to fluoride in the water because the quality of the study is low. These studies measured fluoride in drinking water and IQ in children at the same time. For example, it is possible that parents with higher IQs may have moved from areas to avoid high-fluoride water because of its known risk to teeth and bones, and thus, the absence of high-IQ families may be driving the association rather than the other way around. . This potential bias is sometimes known as the “cart before the horse” bias. Also, studies conducted on animals and humans cannot explain how fluoride affects the brain.

We published a study titled “Association between low fluoride exposure and children’s intelligence: a meta-analysis relevant to community water fluoridation.” In this research, we answered the research question: Does exposure to fluoride, which is recommended for the prevention of tooth decay, reduce children’s cognition and intelligence scores? Fluoride at 0.7 mg/L is recommended for American community water supplies.

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

A A recent Australian study By Du et al. It reconfirmed findings from Canada, New Zealand, and Spain that IQ scores are similar in fluoridated and nonfluoridated areas.

Bruce Lanphier

An epidemiologist at Simon Fraser University who has lesson How pregnant women’s exposure to fluoride may affect their babies’ later development.

Fluoride is a reactive chemical that binds strongly to calcium and minerals. In 1944, the Journal of the American Dental Association described fluoridation as “astonishingly attractive” for preventing tooth decay, but warned of the dangers of adding a “highly toxic substance” to drinking water. Today, more than 70% of Americans drink tap water fluoridated at about 0.7 (parts per million, or ppm), 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 (such as Prozac, Lipitor), and pesticides. Insectivorous. Processed products such as raisins. Over the past 50 years, fluoride intake has increased, contributing to an increase in dental fluorosis – discolouration or staining of teeth due to excessive exposure to fluoride during development.

What did the study find?

Taylor’s team reviewed 74 studies from 10 countries linking fluoride exposure to IQ scores. While many of the early studies were of lower quality, a meta-analysis of high-quality research revealed that a 1 ppm increase in urinary fluoride was associated with a 1.2-point lower IQ in children, even at levels below 1.5 ppm. Although these declines in IQ are small, they have large population-level implications, especially for children exposed to other toxic chemicals, such as lead or air pollution.

Are these findings relevant to fluoridated communities?

Critics argue that no IQ deficit has been found at water fluoride levels below 1.5 mg/L, but this is misleading. First, no clear threshold has been defined. Second, water fluoride is just one source of exposure, and the total amount of fluoride must be taken into account to assess risk. Urinary fluoride, a snapshot of total fluoride intake, has been shown to significantly reduce IQ in children at concentrations common in fluoridated populations.

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

Does fluoridation protect against tooth decay?

It is time to critically review the benefits of fluoride. 2024 update Cochrane review They found little benefit from water fluoridation in studies conducted after 1975, when fluoride toothpaste became widespread. Fluoride’s cavity-preventing effects are primarily local, not systemic, and provide no benefit until teeth emerge.

Should you be worried?

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

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

By taking these steps, you can reduce fluoride exposure during critical growth periods.

Sarah Evans

An assistant professor of environmental medicine and climate science at the Icahn School of Medicine at Mount Sinai, he studies how people’s exposure early in life can affect behavior and cognition.

It is important to note that none of the studies included in the meta-analysis (NTP) were conducted in the United States, where the recommended fluoride concentration in drinking water is 0.7 mg/L – 50% less than the fluoride exposure measured in most communities where It has been studied. While more studies are needed to examine the effects of exposure to a lower level of fluoride, by 2023 Meta-analysis No link has been found between fluoride and child IQ in communities where drinking water levels are similar to those in the United States.

While there are no studies yet that indicate a risk of harm at the 0.7 mg/L of fluoride most commonly found in drinking water in the United States, an estimated 2.9 million Americans and 180 million people worldwide may be exposed to fluoride at levels above the guidelines. WHO guidelines due to the presence of high levels of natural fluoride in some areas. Individuals residing in these areas may be at greater risk of exposure to levels associated with lower IQ of the child in the study. Additionally, the inclusion of fluoride in dental products and treatments as well as its natural presence in some foods and beverages may result in higher than recommended daily exposures. Comprehensive studies that measure individual levels of exposure in the US population from all sources of fluoride are needed.

While about three-quarters of the United States’ water supply is fluoridated, the practice is not mandated by the federal government and is subject to state or local control, so fluoridation practices vary widely across the country. For example, 99.9% of Kentucky residents get fluoride in their drinking water compared to only 16% of New Jersey residents. Individuals interested in knowing the level of fluoride in their drinking water should contact their water supplier. If you live in an area with a high concentration of 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 source or a private well that does not contain fluoride, it is important to practice good dental hygiene through the use of fluoride toothpaste, mouthwash, and regular dentist visits.

The results of this study will likely lead to an increase in the number of communities wondering whether water fluoridation should be stopped. Although there is some evidence that the advent of fluoride-containing products and improved access to dental care has reduced the need for fluoridated water, several studies show a significant increase in childhood tooth decay and the need for dental treatments in communities that have removed fluoride from their water. Drinking. This indicates that water fluoridation remains an effective and necessary public health intervention.

While a recent meta-analysis by Taylor et al. It suggests detrimental effects of exposure to high levels of fluoride on brain development, and it highlights the need for well-designed longitudinal studies that measure fluoride exposure at the individual level over time to confirm whether associations with IQ or other neurodevelopmental outcomes persist at low levels. Which people with high levels of fluoride suffer from. Most Americans. Additionally, it highlights the need to investigate practices that reduce the risk of fluoride exposure above recommended levels in areas where natural fluoride levels are high and to reconsider practices that increase access to routine dental care.