Should we put fluoride in our drinking water?

BREVARD, N.C. (FOX CAROLINA) — Tucked in the Blue Ridge Mountains of North Carolina is a small city with local shops, a laid-back downtown and an outdoor oasis known for white squirrels and waterfalls. But when visitors come to Brevard, there is something they won’t find — fluoride in the tap water.

Maurice Jones, a former city council member, is a key reason it has stayed that way.

“After I did my research, I think one of the main concerns that I had was what it could possibly do to a child’s body,” said Jones, who has four children ranging in ages from 8 to 13.

One of his kids has hypothyroidism, a condition where the body doesn’t make enough thyroid hormones. This can slow everything from heart rate to digestion. Jones points to studies that show elevated levels of fluoride in drinking water can impact thyroid function.

Understanding fluoride levels and health impacts

Susan Richardson, a professor of environmental analytical chemistry at the University of South Carolina who has studied fluoride, said the natural mineral is found in soil, water and rocks. It’s also in various foods that absorb the fluoride from the soil. Tea, for example, can have high concentrations.

“So it’s a natural chemical, if you will,” Richardson said.

Doctors have found that at low levels, fluoride can help prevent tooth decay. But too much is bad. It can cause fluorosis, a condition where teeth get mottled with white, yellow and brown splotches.

Richardson said the level of fluoride a person consumes matters. According to the EPA, the recommended level in drinking water is below 0.7 milligrams per liter.

In a systematic review that analyzes several current studies, it was found that high levels of fluoride in drinking water — 2.0 milligrams per liter — may be associated with thyroid disruption.

“That’s more than twice, you know, it’s more than three times, I guess, the amount,” Richardson said. “It’s not clear whether people that are just drinking the normal tap water that has 0.7 milligrams per liter in it are gonna have any thyroid effects.”

A meta-analysis published in 2025 found that levels higher than 1.5 milligrams per liter may be associated with a drop of 1.6 IQ in children. But it also found there was insufficient data to determine if the lower fluoride level of 0.7 milligrams per liter caused any impacts.

“I think that, as I mentioned, that 1.6 point drop in IQ is very small when you talk about the big range of 85 to 115,” Richardson said.

Richardson said all these studies are observational, which means there could be other factors at play, and association does not mean causation. The authors of these studies say the data available were either considered moderate or weak.

Jones said he remains concerned.

“There might be some kid who, you know, drinks more water than others. So how do you go in and determine, okay, yeah, we’re at, you know, a good level of fluoride in the water,” Jones said.

Richardson said if parents are concerned about their child drinking a lot of water with fluoride in it, they could consider bottled water. Bottled water usually does not have fluoride, so if consumption is high, she said it’s okay to cut down on fluoridated tap water.

Topical fluoride use continues

Jones doesn’t believe fluoride is all bad. His kids use toothpaste with fluoride in it every day and they see a dentist twice a month.

“I want to make the decision as a parent for my children that, you know what, they’re going to have good dental health. We’re going to brush, floss on a regular basis, make sure they have that fluoride topically,” Jones said.

Studies show fluoride in toothpaste helps stop the growth of bacteria, which can therefore reduce tooth decay.

Jones said only one of his kids has had one cavity out of four children.

“But it wasn’t bad…she’s really got a sweet tooth,” Jones said.

First randomized controlled trial underway

About five hours away from Brevard is another small city that has decided to take fluoride out of the drinking water — Kinston, North Carolina. But what is unfolding there could be groundbreaking.

It’s called the WaterBEST Treatment Study.

“This is the world’s first randomized controlled trial of fluoride for the prevention of dental decay,” said Gary Slade, a researcher at UNC Adams School of Dentistry.

Most studies on fluoride are observational, meaning researchers reviewed what was happening and spotted patterns. It’s useful but not the gold standard.

“The technical answers are about reducing bias from confounding factors. Meaning, if I study someone living in a fluoridated city and compare them with a group living in a non-fluoridated city, there’s a bunch of other things going on between those two cities that might be somehow altering what I think I’m seeing,” Slade said.

People in another city may be a different age, income, or have poor access to dental care, and this can impact the results.

A randomized control study can control for many of these factors. In Kinston, 200 families have been selected. Half are receiving bottled water with fluoride, and half are receiving it without. Researchers are analyzing the children’s health from ages 6 months to four years.

“And it’s not done by me, it’s not done by the study staff, it’s done by a computerized system. And that also means that me, the study staff, the parents, the kids, they don’t know which group they’re in,” Slade said.

Measuring total fluoride consumption

The study is not just measuring fluoride in drinking water. Researchers are also measuring total fluoride consumption using toenail clippings.

“Now, we expect to see a difference between the two study groups. The children getting non-fluoridated water are still getting fluoride from some other sources, whether it’s foods, or maybe they’re swallowing some toothpaste. But the question here is, are we seeing more total fluoride intake in the fluoridated group compared with the non-fluoridated group?” Slade said.

Slade said they also hope to study other health outcomes of fluoride consumption, like a child’s IQ, if they receive additional funding.

Declining benefits over decades

Slade said in the 1940s, putting fluoride in the drinking water cut tooth decay by 60%. It was seen as a huge health achievement. In the 1970s, as fluoride toothpaste became common, he said the benefit dropped to 40%. By the 1990s and 2000s, studies found it closer to 25%. Researchers believe the benefit has dropped because dental hygiene has improved.

“So people were rightly saying, well, what’s happening nowadays?” Slade said.

Recent studies find one group benefits the most — low-income families.

“So the actual percentage benefit, it was getting closer to 50% benefit in the people living at or below poverty. This was in their primary teeth, in their baby teeth,” Slade said.

Slade is still a firm believer that fluoride in toothpaste is one of the best health inventions of all time. But he’s trying to answer the question if it’s still needed in drinking water. He said this study should help shape future decisions. The results are expected in 2029.

“And that’s why we see it as so essential to have our randomized trial continue and to generate some more rigorous data than anything that exists so far,” Slade said.

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