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The U.S. Toxicology Program just published a study reviewing past research on the safety of fluoride for children. Reporting in JAMA Pediatrics, they found a slight decrease in IQ scores as fluoride blood levels increased. The authors acknowledged, however, that the studies they reviewed had a substantial “risk of bias.” None of the previous research they reviewed was conducted in the U.S., and many of those authors admitted that their research was flawed.
For those reasons, the reviewers said that their work was not intended to address the controversy about fluoridation in public water systems in the U.S. Unfortunately, that disclaimer will not quell, but feeds, the politicized debate about adding fluoride to public water systems.
In November, Robert F. Kennedy Jr., President-elect Donald Trump’s pick for U.S. Health and Human Services secretary, made headlines after he called fluoride “an industrial waste.” He pledged that the Trump administration would advise utilities to stop adding fluoride to public water supplies.
Critics of the new research question both the validity of the studies included in the review and the methodology of the analysis. They are also concerned about the political consequences of the report.
In the government report, the scientists wrote that even a one part per million (ppm, a measure of the concentration of fluoride in water) increase in fluoride in urine was associated with about a one-point drop in a child’s IQ.
Fluoride is a mineral found in soil, rocks, and water. Based on recommendations by the U.S. Centers for Disease Control and Prevention and the World Health Organization, many cities add fluoride to publicly treated water to reduce the incidence of dental caries. Fluoride makes teeth more resistant to acids, inhibits bacterial erosion and replaces minerals in tooth enamel.
The 74 studies in the new review came from 10 countries – 45 from China, where scientists first observed intelligence differences between communities with exposures to differing fluoride levels in water.
Researchers analyzed each study’s scientific methods, including ages of children studied, how exposure to fluoride occurred, and how their IQs were tested.
Some of the most reliable studies were reported from Mexico and Canada. These measured fluoride in the urine of pregnant women, then tested the IQs of their children years later.
The first part of the review included almost 21,000 children from 59 studies. Children exposed to the highest fluoride levels scored 7 points lower on IQ tests than children exposed to the lowest fluoride levels. When researchers tightened their analysis to just the highest-quality studies they found a 3-point difference.
When the scientists analyzed the studies that reported individual measures of fluoride in urine and IQ scores of about 4,500 children, they discovered that a 1 ppm increase in fluoride was linked to a drop in IQ of 1.63 points.
The drop in IQ linked to fluoride is roughly the equivalent of the drop seen with children exposed to leaded gasoline, according to Dr. Howard Hu, a professor of preventive medicine at the Keck School of Medicine, University of Southern California.
It’s more difficult, though, to weigh the risks and benefits of fluoride than lead. Lead serves no purpose. Fluoride serves an important purpose – dental health. Cavities are a significant public health problem that can affect overall health, especially in more vulnerable communities with poor nutrition. No one is currently advising the discontinuation of fluoridation of publicly treated water, but we can expect to see more research and debate on this matter.
Follow the science.
