Most experts recommend drinking fluoridated water to help prevent tooth decay, but questions still remain about fluoride's role in bone health.
About 62% of 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. Ten million Americans, mostly women, suffer from the potentially painful, debilitating disease, and another 18 million are at increased risk due to low bone mass.
Fluoride has been shown to increase the number of cells that build bone. From the 1950s through the 80s, 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.
Some scientists continue to study fluoride as a possible treatment, but studies have shown that, at high, therapeutic doses, the agent upsets the gastrointestinal system and is not consistently absorbed.
"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."
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."
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."
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.
Fewer fractures
–A study published in the
British Medical Journal
in 2000 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%. The Oregon Health Sciences University researchers measured bone mineral density in 9,000 older women and assessed the women's incidence of broken bones and exposure to fluoridated water.
Researchers compared women who had been continually exposed to fluoride for the past 20 years with those who had not. While the Oregon study showed a decrease in vertebrae and hip fractures, it found a non-statistically 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 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 to 30 years.
Regardless of their positions on fluoridation, osteoporosis experts agree that regular exercise, not smoking, and a balanced diet rich in fruits and vegetables and with adequate amounts of
calcium
and
vitamin D
are the best ways to promote bone health.
"Our guidelines," Dr. Cosman concludes, "are consistent with the guidelines people should follow to prevent heart disease and achieve overall good health."
