Fluoride in water, long added to public drinking supplies to prevent tooth decay, has become controversial in some industrialized areas because of concerns that the health benefits do not outweigh the possible dangers of fluoridation.

A new Australian study, however, confirms that fluoride in drinking water prevents tooth decay for adults of all ages, even those who did not drink fluoride in water as children.

The research was conducted by researchers at the University of North Carolina at Chapel Hill and the University of Adelaide, Australia, and published in the Journal of Dental Research.

"It was once thought that fluoridated drinking water only benefited children who consumed it from birth," explained Dr. Gary Slade of the UNC School of Dentistry.

"Now we show that fluoridated water reduces tooth decay in adults, even if they start drinking it after childhood.  In public health terms, it means that more people benefit from water fluoridation than previously thought."

The study analyzed national survey data from almost 4,000 adults selected randomly from the Australian population between 2004 and 2006, comparing levels of tooth decay with where respondents lived since 1964 and matching that data to information about fluoride levels in the local water supplies.

The results showed that adults who spent more than 75 percent of their lives in fluoridated communities had up 30 percent less tooth decay compared to those who lived less than 25 percent in communities with fluoride in the water.

"We should point out that the evidence is stacked in favor of long-term exposure to fluoride in drinking water," said Kaye Roberts-Thomson, a co-author of the study. "It really does have a significant dental health benefit."

Despite this and a large body of evidence that small doses of fluoride promote dental health by preventing tooth decay and cavities, members of some communities are concerned about the presence of fluoride in water supplies, arguing that it may have long-term side effects.

Community water fluoridation began in the United States in 1945, after the decay-preventing effects of naturally occurring fluoride in water was discovered. It was seen as a cost-effective way of promoting dental health in low-income communities without regular dental care.

The Centers for Disease Control and Prevention hail fluoridation of drinking water as one of the ten great public health achievements of the 20th century, and the Public Health Service estimates that every dollar spent putting fluoride in water saves fifty dollars in dental expenses.

Large doses of fluoride over a lifetime can lead to an increased likelihood of bone fractures in adults, but in the small doses present in fluoridated community water supplies, there is no strong evidence of adverse long-term effects worse than discolored tooth enamel.

The Environmental Protection Agency suggests that a safe level of fluoride in water supplies is 2.0 parts per million, though state and local governments can set more strict limits. The EPA conducted its last Six-Year Review of Drinking Water Standards in 2010 with no significant adverse findings about fluoride levels.

Fluoride in drinking water may have its critics, but it seems like its benefits far outweigh the drawbacks.

If you're still concerned about fluoride in your water supply and don't want the extra cost of bottled water, tap water can be de-fluoridated with simple methods like reverse osmosis filtration and distillation filtration. If you go through that effort, make sure to take extra care of your teeth!