On Monday, JAMA Pediatrics published a new research article on the potential effects on infant development of fluoride in our drinking water. In the decades-long controversial debate about whether fluoride is good or bad for human health, this research concluded that fluoride consumed by woman during pregnancy can decrease the intelligence (IQ scores) of their babies.

But before parents get too worked up about the results of this one study, there is a lot to know about fluoride and its essential, but scandalous role in public health — particularly in the United States, Canada, and Europe, where it is intentionally placed in public drinking water.

Why Municipalities Add Fluoride to Drinking Water

Fluoride was first introduced into the American water supply in 1945, when Michigan instructed municipal workers to dump powdered sodium fluoride into the waterworks tanks. From that moment on, one of the greatest public health experiments ever undertaken began in the city of Grand Rapids, Michigan.

At that time, trust in the federal government was high, with children and adults alike volunteering for dental appointments the year leading up to the experiment. The goal was to help prove the cavity-fighting power of fluoride once it was introduced. And it worked. U.S. Public Health Services researchers found significant decreases in tooth decay among children within just a few years of this practice’s inception. Thus, by 1960, 41 million Americans were drinking fluoridated water.

Despite the rapid buy-in and medical consensus, very few people actually knew what fluorides were or what the negative effects could be from ingestion. Sadly, more than 70 years later, the same is still true. Therefore, every few years, medical research asserts we should be for or against the use of fluoride, and the debate begins all over again.

What Is Fluoride?

Fluorides are compounds that are usually combined with a metal — in most cases, sodium in metallic form. Fluoride exists naturally in soil, air, and water, as well as almost all food and common substances such as toothpaste and mouth rinse. Two-hundred million Americans at any given time now consume fluoridated water.

Because it is natural and proven to make teeth stronger and more resistant to decay caused by acid and bacteria, there were — and are — many reasons to embrace its introduction to the masses. Further, since it exists naturally in most fresh and salt water sources, ingesting low concentrations is a natural part of our human interaction with water and food.

In areas where the fluoride content in water is greater than 0.6 parts per million, however, it is not recommended for use. Throughout medical literature, (conflicting) results indicate too much of the substance can lead to a variety of cancers, diminished IQ, birth defects, lower birth rates, and heart disease. For example, in Tanzania water contains dangerously high levels of fluoride and poses a great public health risk.

What makes this newest study so provocative, then, is that it takes place in Canada, where, like in the United States, fluoride is purposefully placed in public drinking water. Thus, many people have no way of knowing how much they are consuming. Further, despite experts determining an “optimal” amount of fluoride to be digested via water, variation exists across the nation — both in the water supply and in the foods and beverages we consume.

The Implications of Fluoride in Pregnancy

This means many expectant mothers are ingesting more fluoride than they know. The study results indicate that “maternal exposure to higher levels of fluoride during pregnancy are associated with lower IQ scores in children aged 3-4 years old.” Moreover, the results indicate that while the difference in intelligence scores was only a couple of points, the spread was wider when comparing those with highest exposure and those with the least exposure, perhaps signaling a dose-response relationship.

Because fluoride crosses the placenta and has been shown to accumulate in brain regions involved in learning and memory, these results are not completely surprising, nor new. In fact, for fetal brain development, including the substance in water has become divisive in both the scientific and lay communities for this exact reason. The authors even note that they confirmed what a 2012 meta-analysis also found: Higher fluoride exposure from drinking water is associated with lower intelligence scores in children.

While the current study acknowledged it had selection issues, and the primary exposures and outcomes were measured with a notable amount of error, the results were still troubling. If true, the effects could last for generations. Not to mention that anyone in the United States alive today could be exposed to higher than necessary levels of fluoride.

Be Informed and Aware

That said, the authors are quick to point out that the majority of fluoride humans consume does not come from water. They named “food, tea, and toothpaste” as large culprits. So while the results are shocking to many, they are not groundbreaking in the larger body of literature studying fluoride in our overall diets. Also, the results are highly sensitive to all the confounding factors at play, which ultimately indicate a greater need to understand the effects of fluoride on the human body — particularly during development, no matter where it comes from.

The editors of JAMA Pediatrics knew this was going to be a highly debated study. An editor’s note accompanying the article describes the difficult decision to publish. The editor commented that due to the sensitivity of the findings, “We subjected it to additional scrutiny for its methods and the presentation of its findings.” But in the end, they agreed the results should exist in the public arena and be open for debate.

There is no reason to panic. There is ample reason to be informed and aware, however. Without any known health benefits of fluoride to babies, and with known potential harms, expectant mothers would do well to decrease or limit the amount of fluoride they consume. It is also important that the scientific community conducts further research to better understand the effects of this substance on human development and health before more people are at risk.