LONDON (AP) – The first examination of 50 years of research on the safety of adding fluoride to drinking water found no evidence of harm, and some experts said the findings should allay lingering fears it could cause cancer, osteoporosis or Down Syndrome.
The review, published this week in the British Medical Journal, involved 214 studies and was the most comprehensive since fluoridation was first introduced in the United States after World War II.
Fluoride opponents dismissed the research, saying it ignored some studies showing adverse effects, such as an increase in bone fractures among the elderly, and did not account for fluoride from other sources.
“This is not the last word on fluoride,” said Paul Connett, a professor of chemistry at St. Lawrence University in New York and a fluoridation opponent. “This is a superficial look and you’ve got to put this in the context that we can’t control the dose. You have to test the fluoride level in people’s bones.”
The research was commissioned by the British government, which is contemplating a nationwide fluoridation program. As in many other countries, fluoride is added to the water in some British communities but not in others.
Worldwide, more than 360 million people live in areas with fluoridated water. In the United States, about 145 million people drink fluoridated water.
Fluoridation, which aims to reduce tooth decay, has been widely debated worldwide since its introduction. Fluoride is also found naturally in tea, fish and other foods, and is added to some tooth pastes.
The researchers, from the National Health Service Center for Reviews and Dissemination at the University of York in northern England, said they looked at every study conducted worldwide on the safety of fluoridated water and eliminated 3,017 they considered flawed.
Their analysis confirmed that fluoridation reduces tooth decay by about 15 percent, but found that it was also linked to dental fluorosis, or mottled teeth, about 48 percent of the time. In 12.5 percent of cases, mottling was moderate or severe, involving brown patches on the teeth. That is a cosmetic condition that can be rectified, said Paul Wilson, a lead researcher.
One of the most lingering suspicions has been that fluoridated water could make elderly people more likely to suffer bone fractures. At extremely high doses, fluoride can eat away at teeth and bones.
“The finding that long-term exposure to fluoridated water does not increase the risk of osteoporotic fractures among elderly people should alleviate remaining concerns about the safety of fluoridation,” said Hannu Hausen, an epidemiologist and dental professor at the University of Oulu in Oulu, Finland, who was not connected with the research.
The fear of osteoporosis has never been based on strong evidence, Wilson said.
“There are some very vociferous groups on both sides that have polarized the debate,” Wilson said. “But we’ve looked at 50 years of the best research and we’ve not been able to find any association with any harm.”
Connett was not convinced, saying tooth decay has been declining since World War II in both fluoridated and non-fluoridated areas. Fluoridation programs aim for a trade-off of only a minor level of mottled teeth, he said, and the study shows that has not been achieved.
“They wanted no more than 10 percent dental fluorosis in the mild stage,” he said. “This study shows they’ve got 48 percent, and 12.5 percent where it is ‘aesthetically unpleasing.’ The program is a total failure.”
Connett also objected to considering mottled teeth a purely cosmetic problem, saying it could be an indicator of a toxic effect. He also said the analysis of bone fracture risk was not thorough enough.
“You want the benefit of fluoride? Brush your teeth and spit it out as soon as you can. Why put it in the drinking water?” Connett said.
According to the World Health Organization, skeletal fluorosis is observed when drinking water contains 36 milligrams of fluoride per liter of water. The WHO recommends about 1.5 mg per liter. In most communities, the concentration is about 1 mg per liter.
Wilson said the studies he examined tracked the effects of up to 4 mg per liter in drinking water. He said people living in a community with a fluoridation program and consuming fluoride from other sources would be getting no higher a dose than that.