This year the British Medical Journal cited the 10 most important medical breakthroughs of the last quarter decade. Surprising, number six on their list was the movement for evidence based medicine or EBM. For those unfamiliar with this concept, EBM preaches that decisions about treatments or interventions must be based on solid clinical evidence, usually from large intervention trials, rather than anecdotal reports.

The most famous example of why EBM is so important relates to the estrogen during menopause controversy. Anecdotal and observational studies suggested that estrogen reduced heart disease risk in older women. However, the Women’s Health Initiative, a large randomized placebo controlled trial, proved that concept to be false, and indeed showed there may be greater risk of heart disease in women using hormone replacement. The reason I bring this to the reader’s attention, is the March 17 headline on the op-ed page of the Bangor Daily News exclaiming that fluoride in the drinking water is harmful to bones and teeth.

Seven years ago, the esteemed medical journal Lancet published a case-control study showing that the risk of hip fracture for men and women living in a community with fluoridated water was no different from those in a nonfluoridated water drinking community after controlling for multiple variables. I was asked to write the editorial for that article and I titled it “Fluoride and Fractures: An ecologic fallacy.”

In part, the reason for the controversy over fluoride and fractures has originated from ‘ecologic’ studies that are not controlled for variables such as genetics or diet that could profoundly affect outcomes such as fractures. In the case of the column Dr. Leo Leonidas, quoting studies from China and elsewhere in obscure journals without appropriate evidence is misleading at best and does more harm than good.

There will never be a randomized trial of fluoridated water to determine it is harmful to health. However, we can employ the principals of EBM to examine the published evidence to date on fluoride and bone. The two strongest studies originate from very large studies of women followed for long periods. The first comes from The Study of Osteoporotic Fractures which has been a landmark effort funded by the NIH to chart the causes of osteoporosis in the U.S. In 2000, the British Medical Journal published results from SOF on fluoride and fracture risk.

The study followed 9,700 postmenopausal women for more than 10 years and found that long-term exposure to fluoridated drinking water did NOT increase the risk of any fracture, and in fact might lower the risk of hip fractures. The second, more recent study was published in the Journal of Nutrition in 2005. It followed 1,300 female residents of three small communities in which water fluoride concentrations varied from low to high. Serum fluoride levels were measured and fractures were assessed. During four years of observation, serum fluoride concentrations that were high in subjects drinking fluoridated water were not associated with bone density or fractures. Hence, there is little support in the scientific community for the March 17 headline.

It is also extremely important to note that the quote on bone brittleness in that article is misleading. The authors of that paper compared 137 teeth obtained from Toronto, Montreal and Brazil (high, low and intermediate fluoride intakes) for their strength characteristics. The senior author, Dr. Mark Grynpas, is a colleague and collaborator of ours at The Jackson Laboratory. He is an expert on mineralization in bone and teeth, and also the importance of genetic determinants of bone strength.

In the paper, the authors do not mention bones (its about teeth!!) and make the statement that genetic and environmental factors contribute to changes in tooth strength, as well as fluoride. Hence, multiple determinants affect the quality of teeth, and unless these factors are controlled for, definitive conclusions cannot be made.

This is a far cry from stating that this paper shows that fluoride may be harmful to bone. In the end, decisions that have long ranging implications on health should only be made when considering all the evidence.

Clifford J. Rosen, M.D., is director of the Maine Center for Osteoporosis Research and Education at St. Joseph Hospital, senior staff scientist at The Jackson Laboratory and professor of nutrition at the University of Maine.