Fluoride: Healthy or Harmful?

April 01, 2025

University Hospitals Rainbow Babies & Children'sExperts in Children's Health

A mother and her toddler filling a glass with filtered water right from the kitchen tap

Fluoride has received a lot of attention in the news lately, which has many people eyeing their toothpaste or glass of tap water with new questions about the fluoride it contains. When it comes to fluoride supplementation, why do you need it, how safe is it and how much is too much?

Medical toxicologist Marielle Brenner, MD, separates myth from fact about this common mineral for dental health.

Why Do You Need Fluoride?

Fluoride consumption is widely recognized as safe, and it occurs naturally in water and foods. The decision to add fluoride to the public water supply goes back to 1945, when evidence from studies began to show that higher levels of fluoride in drinking water helped to dramatically reduce the risk of tooth decay. The risk of dental cavities in adolescents was found to drop by 30 percent once fluoride was added to public water supplies in towns and cities across the United States.

Preventing cavities means more than just maintaining a healthy smile, explains Dr. Brenner. “Problems with our teeth can cause serious infections in the face and neck, and can even lead to a bacterial infection of the heart called endocarditis,” she says.

In addition, oral health problems are also linked to chronic heart disease and high blood pressure, so staying on top of dental hygiene is an important piece of overall preventative health.

How Much Fluoride Is Enough (or Too Much)?

In 2015, the U.S. Public Health Service updated its guidance to recommend fluoride concentrations of 0.7 milligrams per liter in tap water. The maximum safe level of fluoride in water is 4.0 milligrams per liter of water – leaving plenty of room for additional fluoride from food, toothpaste and mouthwash. “We’re not nearing any sort of maximum amount of fluoride consumption in our everyday lives,” explains Dr. Brenner.

Though there is greater public discussion about adding any kind of chemical to food sources – even a naturally occurring mineral like fluoride – Dr. Brenner adds that the amount of fluoride you’d need to consume to get sick is astronomically high. “Anything can be toxic in overly large amounts, even water,” she adds. “But you’d have to intentionally swallow cups and cups of fluoride salts to get sick.”

A Safe Strategy for Dental Health

Fluoride skeptics have pointed to a study linking fluoride supplementation with low IQ; however, Dr. Brenner shares that the study in question was not well done. “It did not control for other factors such as where participants lived, socioeconomic factors or access to healthcare,” she notes.

She emphasizes that decades of scientifically sound studies continue to point to the low risks and high rewards of fluoride supplementation as a strategy to reduce cavities and improve oral health.

The most common issue associated with too much fluoride is dental fluorosis, a discoloration of teeth that mainly occurs in children. Though fluorosis is a cosmetic concern, not a health problem, Dr. Brenner says it can be avoided through the careful use of fluoridated toothpastes.

“For children under three, the right amount of toothpaste is smaller than a grain of rice,” she adds. “For children under eight, it should be smaller than a pea.”