By Alan R. Gaby, MD
Healthnotes Newswire —Whether or not municipal water supplies should be fluoridated has been the subject of vigorous and often emotional debate for decades. Two studies published in this week’s British Medical Journal provide new information about the risks and benefits of adding fluoride to the water, concluding that fluoridation can significantly reduce the incidence of cavities, also known as dental caries.
In addition, contrary to previous evidence, fluoridation does not appear to increase the risk of bone fractures. However, exposure to fluoride during tooth development can result in a relatively high incidence of fluorosis, a mottled discoloration of the tooth enamel.
The first of the new studies was a systematic review of all medical research that assessed the safety and efficacy of fluoridating drinking water. Some 214 studies, published over more than five decades, were reviewed. While the results of these studies varied considerably, fluoridation was, on average, associated with a 14.6% increase in the proportion of children who had no cavities at all. Children living in fluoridated areas had on average 2.25 fewer decayed, missing, or filled teeth than did children living in nonfluoridated regions.1
However, fluorosis was a common finding among people drinking fluoridated water, and the incidence of fluorosis increased with increasing concentrations of fluoride in the water. At a fluoride concentration of 1 part per million—the level that is most common in fluoridated water supplies—12.5% of the population (one person in eight) would have fluorosis severe enough to be considered cosmetically displeasing. Aside from dental fluorosis, no other adverse effects, including no increased risk of cancer, were associated with fluoride exposure.
The second study examined the association between fluoridation and the risk of bone fractures. Scientists have long been concerned about the possibility that exposure to fluoride can promote fractures, because, while fluoride may increase bone density, the new bone that is formed is apparently of poor quality.2 Some previous studies have found an increased incidence of fractures in people drinking fluoridated water,3 4 5 whereas other research has found no increase in fracture risk.6
This new study evaluated 3,218 American women at least 65 years of age who had had continuous exposure to fluoridated water over the past 20 years and 2,563 similar women who had had no fluoride exposure during that time. In the women with fluoride exposure, the average bone mineral density (BMD) at the hip and lumbar spine was significantly higher (by 2.6% and 2.5%, respectively), but BMD was significantly lower (by 1.9%) at the wrist. Compared with nonexposed women, those exposed to fluoridated water had significantly fewer fractures of the hip and spine and a nonsignificant increase in wrist fractures. The authors of the study concluded that long-term exposure to fluoridated water does not increase the risk of fractures.7
Although these studies provide important new information, they are not likely to end the debate over fluoridation. The problem is that, because very little of the fluoridation research is of high quality, definitive conclusions cannot be drawn. Indeed, of the 214 studies reviewed in the new report, not a single one was judged to be of high quality. Fluoridation research typically involves various types of epidemiological (population-based) studies. For example, scientists might compare outcomes in communities that do or do not fluoridate. Alternatively, research might examine the incidence of cavities, fractures, fluorosis, and other factors in various communities before and after they began adding fluoride to the water. However, these types of studies are unable to control for the differences in diet and lifestyle that may be present in different communities, or for the changes that may occur in these parameters with time.
To provide the most reliable information on the risks and benefits of fluoridation, communities would have to be randomly assigned to fluoridate or not to fluoridate their water supplies, and the people living in those communities would not know whether or not their water contained added fluoride, thereby creating a “blinded” study. Given the strong opposition of some people to fluoridation, such studies are not likely to be performed. Consequently, it may be a long time before the risks and benefits of fluoridation are fully understood.
References1. McDonagh MS, Whiting PF, Wilson PM, et al. Systematic review of water fluoridation. BMJ 2000;321:855–9.
2. Danielson C, Lyon JL, Egger M, Goodenough GK. Hip fractures and fluoridation in Utah’s elderly population. JAMA 1992;268:746–8.
3. Kurttio P, Gustavsson N, Vartiainen T, Pekkanen J. Exposure to natural fluoride in well water and hip fracture: a cohort analysis in Finland. Am J Epidemiol 1999;150:817–24.
4. Danielson C, Lyon JL, Egger M, Goodenough GK. Hip fractures and fluoridation in Utah’s elderly population. JAMA 1992;268:746–8.
5. Sowers MR, Wallace RB, Lemke JH. The relationship of bone mass and fracture history to fluoride and calcium intake: a study of three communities. Am J Clin Nutr 1986;44:889–98.
6. Hillier S, Cooper C, Kellingray S, et al. Fluoride in drinking water and risk of hip fracture in the UK: a case-control study. Lancet 2000;355:265–9.
7. Phipps KR, Orwoll ES, Mason JD, Cauley JA. Community water fluoridation, bone mineral density, and fractures: prospective study of effects in older women. BMJ 2000;321:860–4. Alan R. Gaby, MD, an expert in nutritional therapies, served as a member of the Ad-Hoc Advisory Panel of the National Institutes of Health Office of Alternative Medicine. He is the Medical Editor for Clinical Essentials Alert, is the author of Preventing and Reversing Osteoporosis (Prima, 1994), and co-author of The Natural Pharmacy, 2nd Edition (Healthnotes, Prima, 1999), A–Z Guide to Drug-Herb-Vitamin Interactions (Healthnotes, Prima, 1999), Clinical Essentials Volume 1 and 2 (Healthnotes, 2000), and The Patient’s Book of Natural Healing (Prima, 1999). Currently he is the Endowed Professor of Nutrition at Bastyr University of Natural Health Sciences, Kenmore, Washington.