Is Fluoride Good for Teeth and Bones?
For her study, Phipps recruited women who lived in four Michigan communities from 1950 to 1994. The researchers looked at each woman's household water supply to determine which women had been exposed continuously to fluoridation, those whose exposure had been mixed over the years, and those with no exposure.
All women received bone-mineral density tests (tests that are commonly used to help diagnose osteoporosis) of the spine and femur, says Phipps. Questionnaires helped establish each woman's fracture risks, asking such questions such as what drugs and supplements they took, how many children they had, whether they were in menopause, and whether they had a history of fractures. The women were also asked about their activity levels.
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.