No one debates the many dental benefits of fluoride. They are widely established and scientifically backed. But in recent years, concerns have been raised regarding the appropriateness of the widespread addition of fluoride to drinking water and salt in North America.

Now, a study published by Mount Sinai researchers in Environment International asserts that fluoride exposure may lead to a reduction in kidney and liver function among adolescents.

The study examined the relationship between fluoride levels in drinking water and blood with kidney and liver health among adolescents. The group of young people was participating in the National Health and Nutrition Examination Survey, a group of studies that assess health and nutritional well-being in the United States.

The findings showed that exposure to fluoride might contribute to changes in kidney and liver function among youth in the United States, where 74% of public water systems add fluoride for dental health benefits. Fluoridated water is the primary source of fluoride exposure in the U.S. The findings also suggest that young people who have poor kidney or liver function may absorb more fluoride in their bodies than their healthy peers.

This subject is important to study because a child's body excretes only 45% of fluoride in urine via the kidneys, while an adult's body clears it at a rate of 60%, and the kidneys accumulate more fluoride than any other organ in the body. These facts are courtesy of the study's first author Ashley J. Malin, Ph.D., postdoctoral fellow in the Department of Environmental Medicine and Public Health at the Icahn School of Medicine at Mount Sinai.

"This study's findings suggest that there may be potential kidney and liver health concerns to consider when evaluating fluoride use and appropriate levels in public health interventions," said Dr. Malin. "Prospective studies are needed to examine the impact of chronic low-level fluoride exposure on kidney and liver function in the U.S. population."

This study's findings, combined with other previous studies of childhood exposure to higher fluoride levels, show there is a dose-dependent relationship between fluoride and kidney and liver function. The findings, if confirmed in other studies, suggest it may be important to consider children's kidney and liver health in drafting public health guidelines in the future.

Potential health side effects include renal system damage, liver damage, thyroid dysfunction, bone and tooth disease and impaired ability to metabolize protein.