Fluoride in Drinking Water

Experts recommend drinking fluoridated water to help prevent tooth decay, but questions still remain about fluoride's role in bone health. Many communities in the United States add fluoride to their drinking water to prevent tooth decay. Some scientists have raised concerns about fluoridation's relationship with osteoporosis, a disease that gradually weakens the bones and increases the chance of fractures.

The Paradox of Fluoride and Bone Density

Fluoride has been shown to increase the number of cells that build bone. From the 1950s through the 1980s, sodium fluoride was often suggested as a treatment for osteoporosis. But in the 1980s, Mayo Clinic researchers discovered, during controlled trials involving postmenopausal women, that fluoride increased bone mineral density but also increased the incidence of fractures, especially in the lower extremities. Research since then has been conflicting so fluoride therapy is still contraversial.

"The thinking is that the bone quality formed under the influence of fluoride is not normal. It gets incorporated in the crystal and changes the crystal's structure and stimulates production of a different kind of bone," says Dr. Cosman, clinical director of the National Osteoporosis Foundation. "Fluoride may impair the mineralization of bone. Bone quality may be abnormal even though bone mass goes up."

Fluoride in Water vs. Straight Fluoride

Robert R. Recker, MD, coordinator of the Osteoporosis Research Center at Creighton University in Omaha, Nebraska, cautions that fluoride given as a treatment differs from water fluoridation.

"The Mayo Clinic treatment trials are not pertinent to water fluoridation," says Dr. Recker. "Fluoridation in the water is not a risk. And fluoride as a treatment may still pan out. It hasn't been given an adequate trial with the proper formulation."

A Look at the Research

Just a sampling of the literature on fluoride and bone health shows conflicting results.

More Fractures

In a 1992 issue of the Journal of the American Medical Association, University of Utah researchers reported a study comparing the number of fractures in older adults who resided in areas with and without fluoridated water. The authors concluded, "We found a small but significant increase in the risk of hip fracture in both men and women exposed to artificial fluoridation at 1 ppm (part per million), suggesting that low levels of fluoride may increase the risk of hip fracture in the elderly."

Another study published in 2000, showed that fluoride did not prevent vertebral fractures, and that increasing fluoride doses was associated with increased risk of non-vertebral fractures and gastrointestinal side effects.

Equivalent Rates of Fracture

German researchers reported in 1998 that drinking fluoridated water did not affect bone mineral density and may decrease osteoporosis-related hip fractures in people over age 85.

In a more recent study, done in 2006, researchers studied 1,300 women in three small communities that had fluoridated water. Researchers concluded that "long-term exposure to fluoride did not demonstrate an association with bone mineral density or the risk of bone fracture."

Fewer Fractures

According to a study published in 2000 in British Medical Journal, water fluoridation did not appear to increase fracture risk for older women. The 9,704 women were over 65 years old and were followed for an average of seven years during the study. The study found that long-term exposure to fluoridated water cut the risk of hip fractures by 31% and the odds of breaking a vertebrae by 27%.

While the Oregon study showed a decrease in vertebrae and hip fractures, it found a nonstatistically significant increase in the number of wrist fractures.

"Fluoride seems to redistribute the mineral content, making one bone stronger but another a little bit weaker," explains lead author Kathy R. Phipps, DrPH, an epidemiologist at Oregon Health Sciences University. "But there are about 50,000 deaths per year from hip fractures, and twice that number of people are put into nursing homes because of hip fractures. People don't end up in a nursing home when they break a wrist."

The Need for More Research

The Oregon research is part of a larger study evaluating associations between broken bones and different factors that might increase or decrease fracture risk. Such studies help researchers formulate hypotheses, but this type of study cannot prove a cause-and-effect relationship. To prove that, scientists would have to take two similar communities, fluoridate one, and follow both for 25-30 years.

Ways to Prevent Bone Loss

Regardless of their positions on fluoridation, osteoporosis experts agree that the best ways to promote bone health are:

"Our guidelines," Dr. Cosman concludes, "are consistent with the guidelines people should follow to prevent heart disease and achieve overall good health."