Is Fluoride Good for Teeth and Bones?
Phipps found that women with continuous exposure to fluoride had increased bone mass in their spines and upper legs; she also found that the same women had decreasedbone mineral density in their wrists. They also had fewer fractures of the spine, hip, and upper leg, but had more wrist fractures than women with no exposure. The findings for the women with "mixed exposure" to fluoride did not differ from those in women with no exposure.
Time frame is essential in fluoride studies, says Phipps. "The benefits of fluoride are cumulative, and these were women with minimum of 20 years of exposure," she tells WebMD. "It takes a prolonged exposure to see the benefits."
But one expert says he is not convinced that drinking fluoridated water leads to stronger bones.
"I think it would be a wildly optimistic assumption that because fluoride is good for your teeth, it's also good for your bones," long-time fluoride researcher Paul Connett, PhD, tells WebMD. "The numbers of wrist fractures [Phipps] found were not insignificant. These increases in wrist fractures are raising a huge red flag."
Fluoride indeed increases bone mineral density, up to a point -- but high doses makes bones more brittle, says Connett, a professor of environmental chemistry and toxicology at St. Lawrence University in New York. "We know much about the biological mechanisms that make this happen," he says.
So how much fluoridated water you drink does make a difference, says Connett. "Keep in mind that 50% of all the fluoride you ingest is going into your bones. ... It's really a no-brainer. If you want fluoride, brush it on your teeth and spit it out. What you shouldn't be doing is swallowing the stuff. The worst thing people could do is start chugging this stuff and do themselves damage. It's cumulative over your lifetime."
But an editorial published along with Phipps' study says that water fluoridation may be an answer to osteoporosis, a major public health problem. "There seems to be reasonable strong evidence that an optimal amount of fluoride in drinking water -- either added or occurring naturally -- does not increase the risk of osteoporotic fractures in elderly people. ... Fluoride seems to be the only drug capable of increasing ... bone mineral density," writes Hannu W. Hansen, a professor in the Community Dentistry Institute at the University of Oulu in Finland.
Because study results have been conflicting, though, Hansen writes that "the true value of the gain in bone mineral density remains questionable." Conflicting results may be caused by biases in studies, by the need for calcium supplements in addition to fluoride, and by the fact that high fluoride doses may be harmful and low doses beneficial, says Hansen.